Technical Service Bulletins

EVAP small leak DTC P0442

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The following diagnosis might be helpful if the vehicle exhibits a P0442 DTC, but a system leak cannot be verified through system testing instructions listed in the service manual. The difficulty in determining the cause of the EVAP leak results in improper repairs and customers returning for the same issue.

This applies to 2010 and prior passenger cars and trucks (including Saturn, Saab and Hummer H2 and H3.


The following information outlines the process to perform an EVAP emissions leak test using the EVAP Pressure/Purge Station J 41413-200.

1. Do not disturb any of the fuel system components after verification of a P0442.

2. Connect the Tech II to the vehicle and command the EVAP system CLOSED.

3. Change the tank pressure sensor units from in_H2O to mm_Hg for better resolution.

4. Start the engine and monitor the tank pressure sensor output value for approximately two minutes.

5. If the tank pressure sensor value DOES change (shows vacuum):

*  Remove the purge solenoid from the vehicle.

*  Pressurize the fuel tank side of the purge solenoid with J 41413-200.

*  Add smoke and allow pressure to stabilize for two minutes.

*  If smoke is allowed to pass through the purge solenoid, replace the purge solenoid.

6. If the tank pressure sensor value DOES NOT change:

*  Install CH-48096 adapter between the purge line from the canister and the purge solenoid. Do not use any other adapter or pressurization method.

*  With the EVAP system CLOSED, pressurize the system through the CH 48096 adapter and allow the system to completely stabilize for a minimum of five minutes.

*  Add smoke to the system with J 41413-200 after system stabilization.

*  Review all of the critical interfaces for any smoke (purge solenoid - engine side; remove quick connect or unbolt from manifold; fuel cap; canister vent solenoid filter or fresh air line; any EVAP line quick connects; additional locations)

7. Make appropriate repairs based upon test results.

GM advises that you follow this diagnostic process thoroughly and complete each step. If the condition is resolved without completing every step, the remaining steps do not need to be performed.


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