I've a check engine light with code PO440 EVAP

FINCLADVIS

MEMBER
2002 TOYOTA TACOMA
144,000 MILES

I've a check engine light with code po440 EVAP. I've done smoke tests and no leaks in the lines, replaced fuel filler assembly, charcoal canister, two VSV values under the hood (engine) and the problem still persists. I've not replace VSV valve attached to canister and I'm running out of things to replace. Ironically the check engine light seems to come once the gas tank registers 1/2 tank or less? VERY FRUSTRATED. Can you help?

thank you!
John

2 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

P0440 - Evaporative Emission Control System Malfunction

CIRCUIT DESCRIPTION

The vapor pressure sensor, VSV for canister closed valve (CCV) and VSV for pressure switching valve are used to detect abnormalities in the evaporative emission control system.

The ECM decides whether there is an abnormality in the evaporative emission control system based on the vapor pressure sensor signal.

DTC Detecting Condition

DTC P0440 is recorded by the ECM when evaporative emissions leak from the components within the dotted line in Fig. 1, or when the vapor pressure sensor malfunctions.

Wiring Diagram

CONFIRMATION READINESS TEST

First Trip Procedure

Vehicle must be cold, ambient temperature approximately between 50 °F - 95 °F.
Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) sensor almost same value.

Clear DTC's.

Disconnecting the battery terminals or EFI fuse.
Readiness tests will show INCMPL (incomplete).

Drive the vehicle according to LA#4 drive cycle. Note the state of Readiness Tests. They will change to COMPL as the evaluation monitors operate and if the system passes. This procedure may take approximately 20 minutes or more.

NOTE: Do not shut off the engine - the results will be invalid.

Pass Condition - No Problem Found by the ECM

If the EVAP evaluation monitor shows COMPL, go to the Non-Continuous Test screen.

NOTE:
Do not shut off the engine - the results will be invalid.

To get there, go to Advanced OBD II, On-board Tests, Non-Continuous Tests.
If all of the tests in the time $02 category Tests show Pass, the evaluation monitor has operated and no problem was detected.

Fail Condition - Problem Detected by the ECM

If the EVAP evaluation monitor shows INCMPL, go to the Non-Continuous Test screen.

If all Tests show Pass, the following may have occurred.

The EVAP evaluation monitor did not operate.
The EVAP evaluation monitor did not finish.
The ECM withheld judgement.

If one or more of the tests in the time $02 category show Fail, the EVAP evaluation monitor did operate and the ECM detected a problem.

Go to Continuous Tests screen. This is the only place DTC's are listed for the first trip

NOTE: The DTC listed may not be valid. A second trip is needed to confirm the DTC.

Second Trip Procedure

Vehicle must be cold, ambient temperature approximately between 50 °F - 95 °F.
Go to Readiness Tests screen.
Drive the vehicle according to LA#4 drive cycle. Note the state of EVAP evaluation monitor. This procedure may take approximately 20 minutes or more.

NOTE: Do not shut off the engine - the results will be invalid.

If Readiness Tests changes to COMPL, the EVAP evaluation monitor has operated. Check for any stored DTC's.

If a DTC has stored, the problem has been detected and confirmed by the ECM.
If no DTC was found, the EVAP monitor operated but no problem was detected.

Step 1

Step 1(continued) - 5

Step 6 - 8

Step 9 - 11

Step 12

INSPECTION PROCEDURE

HINT:

If DTC P0441, P0446, P0450 or P0451 is output after DTC P0440 or P0442 first troubleshoot DTC P0441, P0446, P0450 or P0451. If no malfunction is detected, troubleshoot DTC P0440 or P0442 next.
Ask the customer whether, after the MIL came on, the customer found the fuel tank cap loose and tightened it. Also ask the customer whether the fuel tank cap was loose when refuelling. If the fuel tank cap was not loose, it was the cause of the DTC. If the fuel tank cap was not loose or if the customer was not sure if it was loose, troubleshoot according to the following procedure.
Read freeze frame data using hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. At the time of the malfunction.
When the ENGINE RUN TIME in the freeze frame data is less than 200 seconds, carefully check the vapor pressure sensor.

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here is the flow chart we use. Stop throwing parts at it, it would have been cheaper to get a real diag and replace the real issue.

Dont replace anything else till you find the problem

Roy