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Old 09-01-2010, 04:52 PM   #1 (permalink)
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Check Engine Code 450 / 451

I have a 97 T-100 3.4L v6 and my check engine light just came on with codes 450 / 451. This was immediately following a timing belt change although I do not know that the two are related.

The codes come up as an evaporative emission issue which has to do with burning off the fumes on top of the gas tank. I checked the gas cap, and took it off and re-tourqued it (although it was not loose). I cleared the code and it came back within 50 miles... Most likely will start troubleshooting tomorrow (when it's not raining)....

I think I know where to start, most likely the valve on top of the canister for evaporative emission control (had this fail in the past), but any help / suggestions would be appreciated.

Thanks,

Marc
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Old 09-01-2010, 06:27 PM   #2 (permalink)
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Codes are usually with a P and 4 digits...so yer codes should be P0450 and P0451.
How to test yer sensor...

Check all yer evaporative lines...could be a bad hose. Also, check the wiring to the sensor...there could be some corrosion on the contacts or a broken/nicked wire.

The gasket on the gas cap can go bad. Best thing to do is have it tested.
Part number fer the gas cap gasket is 77316-16010.
Looking up that part number on www.toyotapartsales.com I came up with this:

7731616010 $14.52 $0.00 $10.48
Fuel system - Fuel system components - Fuel cap - Gasket
Gasket 1993 - 1998

A complete gas cap w/gasket was listed as part number 77310-35080 and looking that up I came up with this:

7731035080 $25.78 $0.00 $18.60
Fuel system - Fuel system components - Fuel cap
Fuel cap 1993 - 1998

Gary (Parts Manager) from Toyota of Newnan will give you 30% off of MSRP and only charge you fer actual shipping plus a few dollars fer packaging. He seems to have the best deal. Contact him fer more info...
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Old 09-01-2010, 07:11 PM   #3 (permalink)
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Piccie of my vapor pressure sensor...


Part number is 89460-0w020.

From www.toyotapartsales.com...

Item Number MSRP Core Price Price
894600w020 $195.71 $0.00 $141.19

SENSOR ASSY, VAPOR P
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Old 09-02-2010, 09:47 AM   #4 (permalink)
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Thanks Bam,

I'm fairly certain it is the vapor pressure sensor, but the tubing doesn't look the greatest. Thanks for the link, and I was able to order the part (and not pay shipping) as I can pick it up of Toyota of Dallas. Thanks again, as I'm pretty sure if I would have called them directly they would have charge me MSRP (Toyota of Dallas, that is). The gas cap is holding pressure as you can hear / smell it when I take it off...

Marc
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Old 09-02-2010, 05:28 PM   #5 (permalink)
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Did you test yer sensor yet? I'd try that before buying it...

No prob...just click that "Thanks" button...if you don't mind.
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Old 08-08-2012, 01:55 PM   #6 (permalink)
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Did you test yer sensor yet? I'd try that before buying it...



How do you test the sensor?
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Old 08-08-2012, 02:06 PM   #7 (permalink)
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Quote:
Originally Posted by Heliroy View Post
Did you test yer sensor yet? I'd try that before buying it...



How do you test the sensor?
According to the FSM, you measure the resistance on the +B and HT pins. Resistance should be between 5-7 ohms at 68F (M/T Bank 1 Sensor 1--Downpipe sensor) or 11-16 ohms at 68F (Others--post catalytic converter sensor). If the resistance is not as specified, replace the sensor.
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Old 10-01-2012, 12:59 AM   #8 (permalink)
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Wink

So my 1998 T-100 2WD 5vz-fe auto had this code pending. Looking over the diagram, it seems the VPS has a direct link to the gas tank. I wonder if this sensor is gitting contaminated over time and wonder if putting a filter on the lines would extend the life of the sensor. Guess I'll have to experiment on this one and see what I can capture from the lines...

I'm not gonna worry about replacing the sensor just yet as it's only set a pending code once. I will have to test it to see if the sensor is still good.

OBD II Code P0450
Evaporative System Pressure Sensor Malfunction
...

Quote:
OBD II Fault Code

OBD II P0450

Fault Code Definition

Evaporative Control System Pressure Sensor Malfunction

Symptoms

Check Engine Light will illuminate
In most cases, there are no adverse conditions noticed by the driver
In some cases, there may be a noticeable fuel odor caused by the release of fuel vapors

Common Problems That Trigger the P0450 Code

Defective Fuel Tank Sending Unit
Defective or damaged Fuel Tank
Defective Fuel Tank Pressure Sensor, wiring, or computer

Common Misdiagnoses

Fuel Cap
Evaporative Purge Valve
Evaporative Vent Valve

Polluting Gases Expelled

HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog

The Basics
The Fuel Tank Pressure Sensor is a device that tracks any positive or negative pressure changes in the Fuel Storage or Evaporative Control (EVAP) system. It constantly relays this pressure information to the Powertrain Control Module (PCM). The Fuel Tank Pressure Sensor is located on top of the Fuel Tank, or on or near the Fuel Pump and Fuel Gauge Module.

Want to Learn More?
The Evaporative Control system Pressure Sensor code sets when the readings of the Pressure Sensor remain at a fixed value and do not change for ten seconds of vehicle operation after a cold start.

P0450 Diagnostic Theory for Shops and Technicians
The Code P0450 indicates that the Evaporative Pressure Sensor output value is not changing during the EVAP Monitor test and/or the operation of the vehicle. This code uses "two trip" logic, which means that the fault condition must be present during two successive cold starts and vehicle operation.

Common Tests for the Evaluating the Fuel Tank Pressure Sensor

Retrieve the code and write down the freeze frame information to be used as a baseline to test and verify any repair.
Pay very close attention to the Fuel Tank Pressure readings by observing its data stream on a scan tool. Does the Fuel Tank Pressure Sensor work properly? If it doesn't, the system will think that no vacuum is being created when, in fact, there is a vacuum being created that the Fuel Tank Pressure Sensor is unable to read. The Fuel Tank Pressure Sensor is the primary feedback sensor that the Powertrain Computer relies on for the leak test data.
Inspect and test the Fuel Pressure Sensor wiring. Verify that there is a 5-volt reference signal from the PCM, a good ground, as well as a good signal return circuit to the PCM.
While observing the data stream change (or lack there of) on a scan tool, test the Pressure Sensor with a Vacuum Gauge while it is connected to the wiring harness.
If all of the above test results are within spec, then the problem may reside in the PCM itself.
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Old 10-04-2012, 11:58 AM   #9 (permalink)
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After the first morning start, I have noticed my pending code P0450 only shows up around 5 miles regardless of speed and the engine coolant temp around 190F. It doesn't show up during the rest of the day.

It could be possible that the hose is bad. I'll have to do a check and see...
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Old 10-08-2012, 09:22 PM   #10 (permalink)
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Talking

Did some snooping around my evap hoses...and found this.

Split...


All hard and crusty...air plenum side.


Multiple cracks...evap canister side.


Where it was hooked up at...

Air plenum...


Evap canister..


I'll find out in the morning if that was the hose that wasn't doing it's job or not...

Got the hose from AutoZone fer just under $3.
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Old 11-05-2012, 07:48 AM   #11 (permalink)
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Haven't had the pending code fer the VPS since I cycled the electrical connector, flexed the VPS vent, and replaced both the long and short hoses to VSV #1...but strangely enough...I've been gitting a pending code fer the VSV #1 itself, P0446, Evaporative Emmission Control System Vent Control Circuit. I can hear it leaking after I've turned the engine off. Go figure. Tempted to see if I can clean that sucker.
http://www.obd-codes.com/p0446

So now I'm looking to buy a new VSV instead. At least they still make that part.

25860
VALVE ASSY, VACUUM SWITCHING, NO.1
25860‑75100
1
$179.46
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Old 11-05-2012, 12:24 PM   #12 (permalink)
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Fergot to link this thread over at Yotatech that SC T100 had found...
http://www.yotatech.com/f166/p0441-p...-p0451-251680/
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Old 11-05-2012, 12:36 PM   #13 (permalink)
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Looks like a new canister online is about $228 plus shipping. This is supposed to come with all new valves and sensors.

CANISTER ASSY, CHARC
Production date: 1997.08-
Part number: 77740-34071
Replaced by: 77740-34072
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