It is not the codes but the diagnosis

[neelapala]

It is not the CEL codes but the diagnosis that has me concerned. Here is the story..

I just bought a 98 Camry XLE v6 with only 70K miles. Never owned Toyota before. I need to take the car in to get the safety inspection and emissions done for registration. It has a CEL and the codes are as follows:
P0125: Insufficient coolant temp for closed loop control
P1153: Air/Fuel sensor circuit resolution. Bank 2 Sensor 1
P1155: Air/Fuel sensor heater malfunction. Bank 2 Sensor 1

I cleared them to see if they would reappear and they sure did. 3 miles later.

I also had a mechanic some one recommended as reliable(not sure if he specializes on Toyota's) take a look. He pulled the same codes and diagnoised as requiring replacement of an Air fuel mixer thing that was supposedly causing these codes and CEL. He estimated about $350.00 for parts and labor. I was too tired then and was too preoccupied to get the specifics on the part.

Thereafter, I did some research and came across so much info that appears very confusing as a lot of folks seem to be getting this set of codes and very few have expressed satisfactory results.

Is my mechanic getting this right? What do you guys think? Your help shall be appreciated.

[Mister_Perkins]

P1155

Check resistance of A/F sensor heaters (bank 2 sensor 1)
if bad, Replace A/F sensors
if OK Check and repair harness or connector between EFI main relayand A/F sensors (bank 2 sensor 1) and ECM

[pmesfun]

New O2/A/F sensors should take the codes away.
Look at these threads.
1999 Avalon Check Engine Light - P1135 and P0125
For the record : P0125 & P1135

[fenixus]

both Air Fuel Ratio sensors (Heater circuit failure) codes throw the car into a limp (fail-safe) mode. troubleshoot them first (check basiscs first, so see if battery voltage is over 11V, check AFR HTR fuse 20A IIRC in main fuse box and check the AFR HTR relay in small fuse box by battery), replace both AFR sensors with Denso OE items from ebay (cheapest) if necessary.

check for part numbers here (you need Front Left and Front Right, Rear one refers to post-cat sensor under car):
http://www.densoaftermarket.com/cata....php?part=afrs

according to FSM the ECT for EFI sensor (insufficient coolant temperature) doesn't cause the fail-safe mode, but it causes actually more havoc.
The least you can do is to measure the resistance between its terminals and compare with the Toyota ECT resistance/temperature graph. see what temperature they report at cold and what at warm (measure on shut off car). Replace if you find yours falling into wrong temperature ranges. Please replace with OEM sensor from dealer online, they are like $50.



another option is car may have a stuck open thermostat, I think it can throw the same code (Coolant temperature insufficient to achieve closed loop operation). if you plan on replacing it as part of maintenance, please replace with an OEM thermostat and new gasket from dealer (around $15-20). aftermarket thermostats cause people more trouble than good.

[neelapala]

Thanks all.
From what has been suggested, is this something that can be done by a relatively inexperienced but mechanically inclined newbie? I gather that the testing of the battery can be done using a multi meter and probably the same for testing the fuses.
What I am trying to figure out is if this is caused by one issue that triggered all these codes or if these are two separate issues.
All of your suggestions are appreciated.

[fenixus]

if issues are caused by a common source then I can think of only 2 explanations:

a) common ground point is weak somewhere under hood, most likely on the rear or side of V6 engine or behind the passenger side head lamp and breaks the circuit intermittently throwing those codes on crucial sensors.

check this thread for location of ground points (bolts with black-white wires attached to them):
Preventative Maintenance: Engine Grounds

b) engine computer is faulty or has other problems (e.g. wrong inputs somewhere else) causing the above to appear.

otherwise they sound like 2 separate issues to my taste.

[carsrus]

Does the car take long to warm up?
Sounds like a bad thermostat and bad o2 sensor. Usually when they throw heater error their bad.

Pretty simple to change $100 in parts and a couple hours the first time around.

[zppeacock]

Toyota's will throw the p0125 code when the a/f sensor is failing. Your best bet is a new sensor. I prefer the oem sensors as I have had better luck with them.

[fenixus]

Originally Posted by zppeacock

Toyota's will throw the p0125 code when the a/f sensor is failing. Your best bet is a new sensor. I prefer the oem sensors as I have had better luck with them.

no they don't. I had both AFR HTR circuits faulty (wiring issues) so I had both P1135 and P1155 and never had the P0125.

P0125 is either stuck open thermostat or bad sensor (or its wiring is bad and affect readings at ECU end) or something else mechanical causing coolant to stay cold (can't thing of anything else except the thermostat).

[zppeacock]

Originally Posted by fenixus

no they don't. I had both AFR HTR circuits faulty (wiring issues) so I had both P1135 and P1155 and never had the P0125.

P0125 is either stuck open thermostat or bad sensor (or its wiring is bad and affect readings at ECU end) or something else mechanical causing coolant to stay cold (can't thing of anything else except the thermostat).

If you look it up on TIS the p0125 can be set because of a faulty a/f sensor. It wont set that code with every bad sensor.

Check this link out, read page 1 , I know its for a Tacoma but it shows how and when the p0125 is set.

http://www.parksoffroad.com/tacomamo...de/cip0125.pdf

[fenixus]

Originally Posted by zppeacock

If you look it up on TIS the p0125 can be set because of a faulty a/f sensor. It wont set that code with every bad sensor.

Check this link out, read page 1 , I know its for a Tacoma but it shows how and when the p0125 is set.

http://www.parksoffroad.com/tacomamo...de/cip0125.pdf

we are talking here about 1mz-fe, not 5vz-fe??

anyways, trouble area for OP's engine on P0125 in deed contains AFR sensor circuit or sensor:
Fuel system
- Injector
- Ignition system
- Gas leakage on exhaust system
- Open or short in A/F sensor circuit (bank 1, 2 sensor 1)
- A/F sensors (bank 1, 2 sensor 1)
- ECM

so I agree, *might* be related (always learning something new).

How do you explain the P0125 did not happen on my 1mz-fe with both AFR HTR circuits open ? It's not a rule that all P1135 and P1155 must cause P0125 (because they didn't on my V6) ... what gives?

it still might be 2 separate issues.

anyways OP was advised to check/replace AFR sensors and wiring (AFR HTR fuse and relay included) first.

[zppeacock]

I know were talking about the 1mz and not the 5vz but thats the only doc I had at the moment.

You said that both your heater circuits were out. The op has a code for the heater circuit (P1355) and a (P1353). Your codes were for the heaters which means that your sensors still were most likely responding to the air/fuel mixture which will not set the p0125.

When the ECM doesn't see the sensor moving, it first thinks that the engine is not warm because it is stuck in open loop. But in reality the engine is warm and should be in closed loop but the sensor inst responding to the air/fuel mix. So it throws the P0125.

I hope that makes some sense.

Edit: I didn't mean to make it seem like its a rule that you will always get this P0125 with the P1355 and P1353 but I reread it and I did word it poorly.

[fenixus]

you're probably right, i'm too tired too look through numbers now (i think I was thinkig about different ones ... or some gremlin swapped the digits). what you say makes sense to me however

[neelapala]

Here is something I discovered a little too late. This car has a history of failing emissions and passing soon after. I am guessing this is some kind of recurring problem. I hope I am not stuck with an emission failing lemon. I haven’t driven enough to see what the mileage is like. Will be able to do that this weekend and get back.
The codes I got were: P0125, P1153, P1155
@carsrus: No I do not think it takes too long to warm up, engine temperature display wise. But it appears a little slow in blowing hot air. Especially, when idle.
I hope one day I will be able to decipher accurately what is going on in these conversations. Also, what is the conclusive way to find out if the thermostat is stuck/not working?

Since I am a newbie, can you tell me if the following steps that I had outlined are what I need to be doing?
1. Test the battery
2. Test the Fuses
3 Replace A/F sensor bank 2 Sensor 1 ( the one in the front by the exhaust manifold correct?)
4. If this doesn’t solve the problem seek professional help.

or seek professional help right away.

In such a case what should I be telling the mechanic or should I just hope he is good and can figure it out.

[fenixus]

Originally Posted by neelapala

Here is something I discovered a little too late. This car has a history of failing emissions and passing soon after. I am guessing this is some kind of recurring problem. I hope I am not stuck with an emission failing lemon. I haven’t driven enough to see what the mileage is like. Will be able to do that this weekend and get back.
The codes I got were: P0125, P1153, P1155
@carsrus: No I do not think it takes too long to warm up, engine temperature display wise. But it appears a little slow in blowing hot air. Especially, when idle.
I hope one day I will be able to decipher accurately what is going on in these conversations. Also, what is the conclusive way to find out if the thermostat is stuck/not working?

Since I am a newbie, can you tell me if the following steps that I had outlined are what I need to be doing?
1. Test the battery
2. Test the Fuses
3 Replace A/F sensor bank 2 Sensor 1 ( the one in the front by the exhaust manifold correct?)
4. If this doesn’t solve the problem seek professional help.

or seek professional help right away.

In such a case what should I be telling the mechanic or should I just hope he is good and can figure it out.

neelapala,

sorry for trouble code numbers confusion last night. what zppeacock said is correct (though he confused trouble codes numbers even more than I did LOL ) and I second it, it makes sense.

if you are not feeling like doing extensive troubleshooting, I would give a shot to AFR replacement. you don't need both of them as I initially thought.

your trouble codes (P1153 and P1155) point strictly to a faulty AFR sensor in Bank 2 (front, the one closer to front end of car).

so go ahead and get the replacement from eBay like this one (based on '98 camry V6):
Denso OE 234-9007

http://cgi.ebay.com/ebaymotors/DENSO...Q5fAccessories
$100 shipped free, genuine Denso part (OEM supplier to Toyota).

or from here:

Amazon

Amazon

$104 shipped free as well.

and get it replaced. you may need to borrow an oxygen sensor socket (free tool loaner program) from local autozone, part number OEM27110 (refundable deposit required, around $20).

unplug it from connector first, remove old one out, install new one in with the copper grease/sealant (new Denso will come with it or may be pre-coated) on threads, tighten it down to ~32ft-lbs, plug it in.

then reset the ECU, easiest by removing negative battery terminal for 2-5 minutes (note it will reset radio and clock too). another way is to pull out 15A blue EFI fuse from Main Engine fuse box under hood on driver side (it will NOT reset the radio nor clock, but will reset the ECU). you may want to clean the battery terminals and posts with a brush wire while there.

re-connect securely and tightly again and fire the car up. check for codes after car fully warms up.

there is a big chance P0125 gets dismissed together with P1153 and P1155. good luck!