Misleading Codes

Robert Diagnostician New York Posted   Latest   Edited  
Case Study
2005 Honda CR-V EX 2.4L (K24A1) 5-spd (GPPA)

2005 CRV with a common P1457 code. Code definition for the P1457 is for an evaporitive emissions leak on the canister side of the system. In case you are not familiar with this evap system Honda splits the evap system into 2 sections. The sections are composed of the tank side and the canister side.

The system is split in half for testing with the use of the bypass valve. The valve can close off the tank system from the canister system so a problem area can be more accurately located. 

The code this CRV set was for a vapor leak on the canister side of the system. The purge would be commanded open and the vent would be closed and and the bypass would be closed to pull a vacuum on the canister parts. A quick vacuum should be achieved and it should hold. This vacuum is to be monitored by the evap pressure sensor. 

To set the code either a vacuum threshold was not acheived or the vacuum was not held for a specific amount of time. 

It is common for this code to set if the bypass solenoid has failed open. When the solenoid is failed open the vacuum is also applied to the tank system. Due to the volume of the tank system the module will interpret this fault as a leak because it takes too long for the vacuum threshold to be met. 

On this vehicle that is not the case. 

I have developed a method of testing these type evap systems that works well for me. 

I attach the smoke machine to the evap vent hose. At this point the purge is closed the bypass is open and the vent is open. While the smoke machine indicates flow I command the vent closed with a scan tool. Flow should stop immediately. Then I command vent open and flow should resume. This part of the test is repeated several times to verify that the vent does not stick Intermittently. 

After the vent test I allow the smoke machine to run until a flow rate of 0 is acheived. If the flow does not stop at this time then there is a leak that needs to be located. Again not the case here with this CRV it held vacuum well

If the flow does stop then the system is sealed. Next step is to command the bypass open. Flow should start again if not then there is an issue with the bypass valve or solenoid or wiring for bypass solenoid. If flow does increase when the bypass is opened it’s on to the final step. 

With the vent still open the bypass off and the smoke machine still on and connected to the vent hose then the purge is commanded open While the flow is at 0 verifying the sealed system. The flow should increase when the purge is opened to max flow very quickly. If flow does not increase quickly then either the purge did not open or the lines are restricted. 

That was the case with this CRV. When the purge was commanded open the flow from the smoke machine did not resume. So there is a problem with the purge valve or lines. Removing the tank line from purge showed flow so the lines are not plugged. 

So a noid light was installed in to the purge solenoid connector and the solenoid commanded on there was no light activation. 

So there is no command for the purge valve. Next power to the solenoid was tested. That was OK. Next step to test the ground command from the module. No ground from module for the purge solenoid when commanded. 

Next step is to access the engine module unplug the connector and manually apply ground for the purge solenoid. With ground applied at the control module connector and power verified at the solenoid there is no activation of the noid light. That verifies that there is a broken wire somewhere between the module and the purge solenoid. 

A close inspection of the engine harness indicates some damage near the firewall pass through grommet.

After properly repairing the harness the solenoid was again commanded on with the scan tool and the noid light illuminated verifying a complete circuit from the module to the solenoid.

Finally an onboard evap function test was commanded with the scan tool which was passed. System operation verified. Codes cleared and road test performed. 

So a code that indicates a vapor leak turns out to be a broken circuit. A good reason to understand the complete system before attempting to diagnose it. 

Ray Diagnostician

Robert, excellent work and presentation!! Ray

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Maynard Technician

That is an excellent way of doing it, I usually fight them with smoking from the opposite end.... I think I like your way much better.

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Angel Technician

Thanks for sharing your case study with us. Working mainly on domestics, Honda’s Evap can be a little tricky. Thanks for giving us background information on the system as well.

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