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Diagnosing and replacing knock sensors on the 3VZ-FE V6

180K views 73 replies 14 participants last post by  norm356 
#1 · (Edited)
Some of this would apply to the later 1MZ-FE V6 also.

Retrieving the error codes:
To read the error codes, follow the instructions on this website. For the '92-'93 V6 Camry which has OBD I, the error codes related to knock sensors are listed below.

52 = Knock Sensor signal, left bank (front, nearest radiator). No number 2 knock sensor signal to ECM for 2 crank revolutions with engine speed between 1,600 and 5,200 RPM.
53 = Knock control signal. Engine control computer (for knock control) malfunction at engine speed between 650 & 5,200 RPM.
55 = Knock Sensor signal, right bank (rear, near the firewall). No number 1 knock sensor signal to ECM for 2 crank revolutions with engine speed between 1,600 and 5,200 RPM.

For the 1MZ-FE, which has OBD2:
P0325 Knock Sensor 1 Circuit Malfunction (Bank 1, firewall-side)
P0330 Knock Sensor 2 Circuit Malfunction (Bank 2, radiator-side)

Diagnosing the source of the error code:
53 is caused by a fault in the ECU per the FSM. I'd interpret that to mean the ECU is bad; replace it.

52 & 55 can be caused by faults in the ECU, the wiring, or the sensors. So it's best to try to narrow it down. The ECU cannot be checked, so the only thing that can be done is to check sensors and wiring. If they check out OK, then replace the ECU.

FYI: Toyota uses "resonance piezo" knock sensors that put out a 7.6 kHz signal at all times, whether the engine's knocking or not. The ECU is constantly looking for this 7.6 kHz signal when RPM is between 1,600 & 5,200, and if it doesn't see it, it throws an error code. Once the code is thrown, ignition timing is retarded (to zero degrees BTDC, near as I can figure out), which cuts HP pretty badly. Here's a youtube video that talks about Toyota's resonance piezo knock sensors:


Checking the knock sensors:
There are two tests that can be performed. One is to check resistance, the other is to check the live signal with the engine running using an oscilloscope.

Checking resistance:
The sensors are located under the intake manifold, which makes them inaccessible without tearing it apart. Fortunately there is a short cable that runs from them out to the front right side of the engine where it connects to the main wiring harness. The pic below shows where this connector is. Unplug it to check resistance at this point in the wiring.



Edit:
Here's a couple pics showing how to find that connector on the 1MZ-FE. It's not nearly as convenient. This first pic shows the cable where it exits from under the intake manifold. I've marked it with a red line.
(Pic lost in transitioning from Photobucket)

Follow that cable to the connector, boxed in red in the pic below. Roughly, it's under the throttle body.
(Pic lost in transitioning from Photobucket)


In the picture below, the knock sensor signal wires are at pin 1 (rear sensor) and pin 2 (front sensor); the other two terminals serve to connect the cable's shielding to ground. Measure resistance from pin 1 to a good ground and pin 2 to ground. I stress *good* ground. I first checked using the front exhaust shield as a ground, and was getting screwy readings. When I checked resistance from that shield to the battery negative terminal, it was nowhere near zero. It *must* be zero; this is important! So I measured to the battery neg terminal to avoid getting a bad reading. The resistance from the sensor's signal wire to ground must be greater than 1 megohm (1,000,000 ohms). If the resistance checks below 1 megohm on either sensor, it's fairly safe to conclude the problem is not the ECU, but it could be the knock sensor or the short cable going to them. If the resistance is infinity (open circuit), there's a good chance the cable is broken or disconnected from the sensor; the FSM does not say this, that's my opinion. On mine, the rear sensor measured 0.300 megohms; bad!



Checking sensor output with an oscilloscope:
Turn on your o-scope and set the time scale to 100 microseconds/division, and the voltage scale to 200 mV/division. With the connector described above unplugged, start the engine. Connect the scope's signal probe to one contact and the probe's ground lead to a good ground. The engine needs to be revved a bit for the sensor to generate a measureable signal; roughly 2k RPM. The FSM says 4k RPM, which I found unnecessary. At idle, they'll put out just a small ripple. A good sensor will put out a signal as shown below. The rear sensor on mine was flat-lined. So I've either got a bad sensor, or the short cable is bad. Either way, the intake tract needs to be taken apart to inspect and replace things.



If you find nothing wrong in either of these checks, either the main wiring harness is bad, or the ECU is bad. To check the main wiring harness, check resistance in the cable connected to the ECU from pin 6 (signal KNK1) to ground, and pin 14 (signal KNK2) to ground. The glove box must be removed to access the ECU. Again, resistance should be greater than 1 megohm. If it checks OK, chances are the ECU is bad. If it checks bad, there's a problem with the main wiring harness... and I have pity on your soul. Good luck finding that problem!

Replacing the sensors & cable:
If you've determined there's a problem with one of the sensors or the short cable going to them, it's time to take it apart and replace things. I decided before starting that I was going to replace both knock sensors and the short cable. This is a big enough job I didn't want to risk having to do it again soon. I ordered the cable and two sensors for ~$300 from ToyoPartsman, Gary Smith at Newnan Toyota. I also ordered a Fel-Pro gasket set for $40 from Rockauto. And a tube of silicone sealant locally for resealing the coolant bypass tube, a "while you're in there" job I highly recommend doing. You'll also need coolant to refill the cooling system when you're done.

Part numbers:
Fel-Pro gasket set = MS95406
Knock sensor = 89615-32030 (this p/n replaces 89615-33020)
Short cable = 82219-33010





First, drain the coolant by opening the petcock at the bottom of the radiator on the engine side. It's circled in the pic below. This is necessary because there are coolant passages in the intake manifold. If it's not drained, when the intake manifold is removed coolant will spill everywhere and make a big mess. Worse, some could drain into a cylinder with open valves and hydrolock it. Don't be foolish, drain it. Google "hydrolocked engine" pics if you feel a need to see bent and busted connecting rods.



Use an allen wrench to remove the two fasteners holding the decorative intake cover (no pic). As shown in the pic below remove the 4 bolts circled in red, unplug the injectors circled in yellow, and disconnect the vacuum lines in green. Set this assembly aside to the right.



Remove the big flexible rubber intake duct running from the MAF sensor to the intake mouth.



Remove the intake plenum 2 bolts and 2 nuts circled in red below. When reassembling, torque these to 32 ft-lb.



Remove the 4 hex huts (reassembly torque 9 ft-lb) holding the ACIS actuator to the plenum. Disconnect the banjo bolt (reassembly torque 11 ft-lb) fuel connection to the cold start injector, and the vacuum line going to the vacuum motor. Set it aside as shown and remove the gasket. Also disconnect the rubber hose going from the PCV valve to the nipple on the underside of the intake plenum. Use the new gasket from the Fel-Pro set on reassembly.



There are 5 fasteners on the backside of the plenum that must be removed. One on the left...



One here...



one here...


And two in the middle (reassembly torque 13 ft-lb), which bolt the EGR pipe to the back of the plenum (see pic later). Mark with a Sharpie, and remove these vacuum lines...



Unplug the ECT sensor (green plug) and the cold start injector timer behind it, both on the left in this pic. On the right, disconnect the throttle position sensor connector, and the IACV connector (blocked from view, it's underneath the rear cylinder circled in blue in this pic)...



Now lift the plenum, and disconnect the three coolant lines underneath shown below. You now should be able to move the plenum to the driver's side of the bay, out of your way (unless I've forgotten something, which is possible, so check). Also, see the EGR pipe I said I would mention earlier?... in the lower left of this pic.



With the plenum removed, STUFF SOME RAGS INTO THE INTAKE MANIFOLD PORTS TO KEEP FROM DROPPING THINGS IN THERE!!! Yes, I meant to yell. It would really suck to drop a washer through an open valve down into a cylinder, and have to remove the head. Then remove the two bolts circled in red and disconnect the three injector connectors circled in yellow, and set the rear injector harness aside to the left...



Disconnect the upper radiator hose and the small coolant hose going from the thermostat housing to the coolant reservoir (no pic). Remove the 8 bolts and 4 hex nuts (reassembly torque 13 ft-lb, work from middle outward, doing it in several passes). Warning: The bolts have two washers each, and the nuts have a captive washer and a loose washer; don't drop them. The short bolts (yellow circles) go in the outer holes, and the long bolts (red circles) in the inner holes. Also remove the bolt holding the ground wire, and a metal bracket. These two are out of view, on the left, next to the thermostat housing). There is one electrical connection (in blue) to undo to the intake manifold. Sorry for not getting everything in this pic, but I had my camera bumped into the hood looking straight down, and this is as good a pic as I could get. Note that you're seeing some things in this pic that shouldn't be there... that's because I forgot to take this pic until I was putting it back together.



Now lift up on the manifold, revealing the knock sensors (in big red circles below). Unsnap the knock sensor cable anchor circled in yellow. Remove the hex nut in the small red circle; this will allow the coolant bypass tube to be lifted out of place.



Remove the two bolts holding the coolant bypass metal tube flange and lift it out. At this point, you can re-check knock sensor resistance to verify which sensor is bad. Before reinstalling the bypass, remove and replace the knock sensors, torquing to 33 ft-lbs. Install the new cable, snapping it into place, and routing it out to the main harness. Reinstall the small hex nut holding that end-plate.



Thoroughly clean the bypass tube flange and the mating surface in the block. Apply sealant to the bypass flange as shown, insert into the block, and replace the fasteners, torquing to 6 ft-lbs.



Remove the old intake gaskets and clean both mating surfaces thoroughly. I also scraped out the carbon in the mouths of the intake ports in the heads. When done, I used a shop vac with a small flexible nozzle to suck out any carbon debris that may have fallen into those ports.



Reassemble in reverse. Torque the new knock sensors to 33 ft-lbs, and don't use any sealant or thread locker. Take your time, double check that everything gets hooked back up correctly. Don't pinch anything under the intake manifold! (*%$*&!!!... I can be such a dope sometimes!) Take lots of your own pics before disconnecting things; that can really save you from getting stuff wrong.

After reassembly, remove the radiator cap at the thermostat housing and refill the system with coolant. Check for leaks, especially at the intake manifold's coolant galleys on each end. With the cap still off, start the engine and top off as needed. Keep watching and topping off until the engine is fully warmed up. And continue to keep an eye out for leaks. You'll see the coolant level drop many times, with an occasional bubble burping out. Keep adding coolant as needed until it won't take any more. This is important, so don't be in a rush! The 3VZ is fussy about air bubbles in the cooling system, and will overheat if you don't get this done properly. Even after doing this, it's a good idea to closely monitor the coolant level in the overflow reservoir for a few days, topping off as needed. I've had to top it off twice in the week since I've finished the job. And the CE light has remained OFF! :clap:

Oh, and here's why you should buy the cable, even if it's not the source of the problem. When I went to disconnect them, the connectors at the knock sensors crumbled like egg shells at the first touch.
 
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#2 ·
Nice DIY, very complete.

What a lot of work to replace a couple of very expensive sensors. It would have probably cost a fortune to have a dealer do it.

I bet you are glad it's finally done.

You might want to sticky this. :D

.
 
#3 ·
Thanks AJ! Yeah, I'm darn glad it's done. It took me 10 or 12 hours. Partly because I'm always slow at this stuff. And stopping to take pics... and putting something on wrong and having to redo it. Like setting the intake manifold on top of a coolant line, pinching it and not noticing until I go to hook it up... "Now where the heck did that go? :confused:... AH CRAP!:facepalm:". :lol:
 
#4 ·
Nice job, and excellent DIY. Great pictures! I might have to take mine apart again some time just to clean and shop vac my intake ports out, the appearance inside the intake plenum and manifold on mine, suggested I probably have a similar cylinder head, port condition.:rolleyes: Hey that probably will give the equivalent of a miny porting job, in itself!:)

One very useful tip on re-assembly, after the intake manifold is back on...
Leave the plenum threaded, but loose and not torqued down, so that it has a little wiggle movement left, to help in re-threading the rear braces and EGR system, in that tight space behind the engine. Personally, I could not get those darn things to align well enough to get the bolts back in without re-loosening the plenum.;)
 
#5 ·
93 Camry "new"/used 3VZ-FE code 55 emission fail

I have a 1993 Camry that had its motor changed twice (long story why). Both times it had a "only 25K miles" used motor installed. The first time it threw a code 55 right after the motor change and I had it fixed ($$). It was wiring to the sensor that is tough to get to as noted in this thread on Toyotanation. The second motor was from the same supplier (only 25K miles) and it likewise threw a code 55 but I was told not to invest in fixing it. I don't mind the drop in performance.

It had a new catalytic and exhaust installed at the same time as this latest motor. The car has overall been well maintained. It is mostly now driven very short distances in the city (3 miles in each direction typical). I've only put about 4K miles on it for each of the past two years since the motor was changed. Recently (June) I drove it on the highway for 5.5 hours in each direction so it has had some exercise. It just failed its smog test recently. I wonder if the retarded timing from the code 55 could be contributing significantly to the failed smog test. The old fuel injectors and sensors were put on the latest motor. It barely passed on the HC on past smog tests (with those same injectors) when it didn't have the code 55 problem.

Since the failed test, I ran 1/2 can of seafoam through the brake vacuum line and I put one ounce of Seafoam per gallon into the tank. I hope that if I burn about half the tank this week that it will do better on the smog test this Saturday.

Prior to the seafoam, the HC limit was 57 and I failed with somewhere in the 60s and the NO limit was in the low 400s and I just barely failed it with the code 55 problem.

Any thoughts/suggestions?
 
#6 ·
The recurring code for the knock sensors makes me think there might be a problem with the main wiring harness. ...Or was your main harness also swapped with the two engines?

I doubt that's why it's failing emissions tho. If it's not throwing any other error codes besides the knock sensors, my first guess would be the upstream O2 sensors are "lazy", and need to be replaced. If you get the Denso "Universal" fit sensors they're really cheap, like $30 each. Universal = same sensor without the connector, which is a single wire in this case, so transferring the connector is easy.

Is it failing for NOx too? That might be a problem with the EGR system.
 
#7 ·
Probably same problem as with first motor change

When the motor was first changed, the check engine light came on after a few minutes of driving, and it threw code 55 the problem was a wiring harness (mechanic charged about about $80 for the part) to the knock sensor. I assume that he changed it using a procedure much like you described on this thread. Lots of labor and cost.

When the motor was changed again (short story why below) by a different mechanic (I moved cities) with the same type of motor (25K miles) from the same supplier, I am likewise getting code 55. The wiring harness that had been put on motor #2 to correct the code 55 was not put on motor #3. I forgot to tell the new mechanic about that problem with motor #2. That was my oversight. It probably would have been far easier for him to change that harness before installing the motor. Oh well...

With motor #3, as with motor #2 before changing that wiring harness, the check engine light comes on after a few minutes of driving. I suspect that the same wiring harness has a problem but of course the sensor (from the old motor, put on the new one) could have since developed a problem.

I got the car good and hot before the e-test with a highway drive. The HC limit was 57 and it registered in the high 60s if memory serves. The NO limit was 421 if memory serves and I was a bit high (about 428).

From past emission tests it has been right on the high limit for HC so I was wondering if there was something simple causing that like dirty injectors. That's why I decided to try running 8 ounces of Seafoam through the brake vacuum line, etc and put one ounce per gallon in the tank. I think that the retarded timing from the code 55 will make HC worse. I hope that the Seafoam will have helped. It's getting re-tested for emissions this Saturday and if it fails again I'll bring it in for diagnostics because my new mechanic doesn't want to change the wire on the knock sensor unless that is the likely reason for the emission test failure.

Any advice/suggestions would be welcome.

I'll post the outcome later for all to see and possibly benefit.

Short story as to why a second motor was installed:

The mechanic who installed it forgot to re-connect the coolant temperature sensor that drives the hydraulic cooling fan. I've learnd that there are three different coolant temperature sensors on the car (one driving the temp reading on the dash, one feeding the ECU, one driving the cooling fan). Sadly the cooling fan coolant temp sensor isn't connected to the ECU so there was no visual indication of it not being connected. Therefore the cooling ECU (a different one) ran in failsafe mode. On a hot summer day in stop and go traffic with the air conditioning on, it overheated and red lined before I noticed the increasing engine temperature. I turned off the car as soon as I noticed. When it cooled down it seemed to be OK. More than a year later I learned that I had a slight head gasket issue that only surfaced in hot ambient driving conditions on longer drives. From my research at the time 3VZ-FEs are known for such non-obvious head gasket issues. I expect that that the over-heat was a contributing factor. By that time I had moved cities.
 
#8 ·
I think the "problem" with 3VZ-FE engines is probably overated as an problem. More likely the "problem" was with owners that neglected to maintain thier cars cooling system properly. Even that first red-line overheating situation could cause the problem because of an iron block/aluminum head, different expansion rates of the metals, alot less forgiving than, Iron & Iron, or Aluminum & Aluminum.

The HC/emmissions failure does sound alot like messed-up O2 sensors though, these sensors can wonder far and wide without causing codes, until they are almost useless. (I've seen filthy plugs, carboned exhaust tailpipes, and terrible milage, and just a code after 2-3 months of driving x 3). -Reset, then nothing for 2-3 months.

Incidently, my car also required a knock sensor replacement at about 120K miles. One done, no problems with that since.:)
 
#9 ·
Might the special ECU OBDI test mode help diagnose O2 sensors?

Thanks for the excellent information. I found http://www.midshiprunabout.org/mk2/why-the-3vz-fe-is-the-best-toyota-v6/ that says:

Why the 3vz-fe is superior
Mostly ECU reasons:
It’s OBD-I ECU is the least trouble code throwing, least caring ECU in the line-up....

It does not throw/store codes from o2 sensor feedback – even if it is massively different. Black smoke rich to engine melting lean. It doesn’t care...

Afraid you’ll miss OBD-II’s anal retentiveness for troubleshooting?
The 3vz-fe has you covered. Tho the ’94 1mz-fe had the world’s first complaint engine/ECU, the 3vz-fe’s do have an ace up their sleeve.
Diagnostic mode II. Yes… The 3vz-fe is the only v6, and one of two OBD-II Toyota’s with DIAG2! This can’t even be entered with the ECU OFF! It has to be done with the engine running! It will throw every code possible instantly. Guess what happens when you trigger it & you’re not moving more than 6mph? Yep, wheel speed sensor code. All your temp & o2 sensors haven’t warmed up? Ya – count all them too. Along with a half dozen other codes.
Anything triggers anything in DIAG2.

It sounds like most people don't know about this special test mode. If I interpret the above correctly, in normal mode the ECU may not report issues with failing O2 sensors but might it be more sensitive in test mode? I would ideally like to test this myself before bringing the car in for expensive troubleshooting where the mechanic probably won't know about or take advantage of the test mode.

From http://www.justanswer.com/uploads/skyvisions/2008-05-01_093302_93_camry_codes.pdf I see on page EG2-173 that "Compared to the normal mode, the test mode has high sensing ability to test malfunctions"...

"First, using SST, connect terminals TE2 and E1 of the DLC2, then turn the ignition switch on to begin the diagnosis in the test mode"

It shows a picture but I cannot tell how to get at the DLC2 now what an SST is. From the picture the SST looks like a fairly simple (and hopefully cheap) jumper setup. Is it a special connector that I can buy and if so, from where? Also how can I hopefully easily gain access to that DLC2 connector? Any pointers would be appreciated.

I will post what I ultimately learn back here.
 
#10 ·
Yes, the SST is just a jumper wire. A paper clip will work. I made one with wire and a couple of small crimp-on spade terminals that stays connected a bit more securely. I've never looked for the DLC2 port. From the images, it looks like it would be left of the fuse box pointing downwards.
 
#11 ·
O2 sensor brand recommendations for 3VZ-FE?

By the way I got into test mode using a paper clip on the diagnostic connector under the hood instead. It was much easier to get at. Even after multiple medium length drives, I never got more than code 55.

Just in case the car's O2 sensors need to be replaced, does anyone have any brand recommendations? I see quite varied pricing such as about $20 for Bosch 11027 (universal) as compared to highly variable pricing (up to $130 in Canada for each of front and rear) for models from Walker, Denso, Standard Motor Products, Ultrapower, APWI, Beck/Arnley, Delphi, NTK, AC Delco, Airtex/Wells. Some were noted for California (more stringent, I assume).
 
#12 ·
Denso, # 234-1053 are from the original parts supplier for Toyota, pretty reasonable in pricing, come with the correct mounting brackets in place and OE style plugs to plug into the cars wiring. There were slightly cheaper brands and parts available, but these were the closest to a direct OE replacement (they are listed as such), and only $20-30 more than other options. Made the job easy as pie, and gave me confidence that good parts were being put back in. (Think it took me about an hour of fiddling around to to the job).:)
 
#13 ·
Timing issue. However performance now awful with code 55

I brought in the car for diagnostics and re-test. The only thing done prior was the use of Seafoam (up the brake vacuum line and in the gas tank, burned 1/2 tank). They adjusted the timing and it passed the smog test. I have the past results from 2003, 2004, 2008, and 2010. The 2012 results for 25 mph driving had the lowest HC by a wide margin. The limit was 57 ppm and it measured 35. I've always been right at the limit in the past except for my recent fail at 64. The NO limit for 25 mph driving was 421 and it measured 185 now versus 428 when it failed recently. The HC at idle went up a bit from 33 to 45 (limit 200).

However it still has the code 55, just as when the motor was changed. When the motor was changed the performance wasn't ideal but it was tolerable. My mechanic convinced me to live with it. Now with the timing adjusted and the code 55, I cannot live with the drop in performance. It is quite hesitant while accelerating. Once it's up to cruising speed it's OK.

So now I'll change the wiring harness and knock sensor as described in this excellent posting on Toyotanation. I hope that it makes a really big difference. I miss the silky smooth power of a well functioning stock 3VZ-FE. I bet it's even better if tweaked.
 
#15 · (Edited)
If you do remove the intake plenum, yes, use a new gasket. But the spark plugs & wires can be replaced without removing the plenum. To get the rear plugs out, use a series of 3/8 inch drive sockets and extensions as follows, from the bottom up:

1) A *good* spark plug socket. One that has the rubber insert that grips the plug securely.
2) 6 inch long extension
3) U-joint
4) 6 inch long extension
5) The ratchet.

I like to assemble 1, 2, and 3 together and drop them down the plug well, then put 4 & 5 on that.
 
#16 ·
Some of this would apply to the later 1MZ-FE V6 also.

Now lift the plenum, and disconnect the three coolant lines underneath shown below. You now should be able to move the plenum to the driver's side of the bay, out of your way (unless I've forgotten something, which is possible, so check). Also, see the EGR pipe I said I would mention earlier?... in the lower left of this pic.



I see part diagram for the water-bypass hoses, I guess the hoses two ends should be


1. 16261: main coolant chnnel branch into throttle body
2. 16264: outlet of throttle body and inlet of IAC
3. 16267: outlet of IAC and inlet of EGR cooler
4. 16281: outlet of EGR cooler and water flow into upper water hose


So I think the middle hose should be No. 5 vacuum air hose that describe in page EG-211 of 3vzfe engine FSM. Is my guess correct? Does anyone give some viewpoints?
 
#17 ·
great thread, excellent info.

i wimped out and took to mechanic (sorry, didn't have time). Also replaced the knock wiring harness. Imagine how PO'ed I am when same CEL is on, same code for knock sensor. According to flow chart it is either wiring or ECU. Good luck seeing a defective/chafed wire. While possbile, I'm highly doubting it.

Real question I have is regarding diagnosis/knock sensor test. I don't have an oscilliscope. I do own a Harbor Freight multimeter. It has 3 or 4 resistance settings: 2000, 200, 20 and the ohm symbol. So which of these will measure "megaohms" as described at the beginning of this thread?

Does the car need to be turned on? running? revved to certain RPM?.... in order to get a reading? I tried the grounding method and got nothing.
 
#18 ·
I did it with the engine off. When you say it read nothing, does that mean it showed infinite resistance? Are you certain it was set to measure resistance?... Not volts?


Sent from AutoGuide.com App
 
#19 · (Edited)
I have DCV & ACV, and i use those settings for voltage. i was set to the ohm section with the greek looking ohm symbol. I tried each of the various resistance settings; I had my black lead on the NEG battery terminal, and I individually checked the 2 brass looking male leads/prongs from the wiring harness, with the red lead.

I will have to double check again on my reading. I think infinity shows as "1" . Probably a low end meter but has always worked when I'm checking ac & dv voltage.

my continuity beeper hasn't worked for a long time.
 
#20 ·
well I just finished an ECU swap between 2 cars I have same model, same year, same ECU part #s. Still didn't fix my CEL, nor did my performance change. My CEL car gives code for knock sensor. It is sluggish in mid range, around 2000 RPM, it is flat when I give it gas. The other car has snap and pep driving exact same way. ALSO, my CEL car gets poor mileage. I also tried seafoam, and cleaned throttle body.

want to sell CEL car, but don't want to dump my problem on someone else.
 
#21 · (Edited)
OK, sounds like the meter is set correctly. Sorry if I offended, but ya never know the level of someone's skills on these boards.

Still getting the knock sensor code after swapping with a known-good ECU?... that kinda narrows it down to the wiring harness between the ECU and the connector for the short harness. You could check resistance from signal wire to ground at either end (disconnect at the ECU-end if you check at the sensor-end). Or visually inspect the harness for problems.

Edit: If the main harness checks out OK, maybe the new knock sensors are bad? What brand of parts were used?
 
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#22 · (Edited)
no BMR, you didn't offend me in the least. i was giving detail in case there was a setting i missed on the meter. I'm not sure which of the resistance values to set it at.

In fact, I really appreciate your thread and gave the thanks i meant to do earlier.

I wondered exact same thing about possibly faulty knock sensors. They are el-cheapo brand. Only need to work long enough to sell car. Couldn't stomach $200 each from our local parts store. Never even checked Toyota price. i will be boiled if they are brand new & faulty. the $85 wiring harness had me miffed.

trying to track the harness will be fun. I suppose if I can figure out which wire on the ECU plug is the corresponding wire on the knock sensor harness end.... I might be able to check for continuity. heck, then I could even run and splice in new wire???
 
#23 ·
I kept my one known-good OEM knock sensor. I doubt I'll ever use it. If you want it, it's yours for the price of shipping. PM me if you're interested.
 
#24 ·
thanks for the offer. I first want to determine what's going on. Can a knock sensor be "bench tested" for the resitance ? be nice to know before installing it that it is working (on the new ones I have). could I set it in a vice and use the vice as ground, then check resistance value?? just thinking out loud.
 
#25 ·
I'm sure you could bench test it like that. If the sensor's internal resistance is wrong, you'd see it. Problem is checking their output.
 
#26 ·
will the oscilliscope show the output & give a better diagnosis?

I tried the test again today. when i set my cheapo meter to 2000k or 200K resistance, it displays "1" or "1." . If i check a piece of meteal or touch the 2 leads together it shows "0.00" for continuity/resistance.

So, when I ground one meter lead to NEG terminal and check both of the brass pins seperately (even checked the silver pins), I show "1". Like it's not registering any resistance at all. These are new sensors and new wiring harness. Shouldn't I get something? Not sure as this is a very basic, cheap meter.

I also checked code again and it is only code 52. I do NOT get code 55. I do not get any other codes.
 
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