Son's 03 threw a check engine light on on his way home tonight. I ran code check and only one C is 10 PCM PO442. I couldn't find this code on my list I have. It happened just as he pushed windshield washer button. Car still has GMPP warr coverage for few miles. All other codes shown were H. Thanks

 

Searched my service manual dvd. Sounds like a small vacuum leak.

P0442
This DTC tests the evaporative emission (EVAP) system for a small leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the vacuum decay rate. At an appropriate time, the control module turns the EVAP canister purge valve ON and the EVAP vent valve ON. This allows the engine to draw a vacuum on the EVAP system. At a calibrated time, or vacuum level, the control module turns the EVAP canister purge valve OFF, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum decay. If the control module detects a leak larger than a calibrated amount, this DTC sets.

Conditions for Running the DTC
DTC P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0443, P0449, P0452, P0453, P1112, P1114, P1115, P1120, P1133, P1134, P1153, P1154, P1220, P1221 are not set.
The ignition voltage is between 10-18 volts.
The barometric pressure is more than 75 kPa.
The fuel level is between 15-85 percent.
The engine coolant temperature (ECT) is between 4-30°C (39-86°F).
The intake air temperature (IAT) is between 4-30°C (39-86°F).
The start up ECT and IAT are within 9°C (16°F) of each other.
The vehicle speed sensor (VSS) is less than 121 km/h (75 mph).
Conditions for Setting the DTC
The EVAP system can achieve vacuum, but a vacuum decay is detected during the diagnostic test.

Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

 

Thanks, will let dealer have a look tomorrow.

 

Have you refueled the car recently? Check the gas cap to insure it is installed correctly. (I always make sure that the cap clicks 3 times when installing.) Also, check the condition of the O-ring gasket on the gas cap. Either of these things can cause the EVAP systems test to fail and the car to throw this trouble code. Once you've checked the cap O-ring and installation, clear the trouble code and see if it returns.

Good luck with the fix.

 

That was it. The purge check valve was stuck open. They replaced it. Thanks