Circuit/System Testing

WARNING: This page is about a different car, the 2008 GMC Yukon and 2008 Chevrolet Tahoe. However, it is still accessible from the selected car via links, so may be relevant.

IMPORTANT: All electrical components and accessories must be turned OFF and allowed to power down.

Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description .
Ignition ON, verify the scan tool hood position parameter displays Open.
- If the hood position does not display Open, refer to Diagnostic Trouble Code (DTC) List - Vehicle for DTC P254F.
Ignition OFF, disconnect the MAP harness connector at the MAP sensor.
Ignition OFF for 90 seconds, test for less than 5 ohms between the low reference circuit pin A and ground.
- If greater than the specified range, test the low reference circuit pin A for an open/high resistance. If the circuit tests normal, replace the ECM.
Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit pin C and ground.
- If less than the specified range, test the 5-volt reference circuit pin C for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
- If greater than the specified range, test the 5-volt reference circuit pin C for a short to voltage. If the circuit tests normal, replace the ECM.
Verify the scan tool MAP Sensor parameter is less than 12 kPa.
- If greater than the specified range, test the signal circuit pin B for a short to voltage. If the circuit tests normal, replace the ECM.
Install a 3A fused jumper wire between the signal circuit pin B and the 5-volt reference circuit. Verify the scan tool MAP Sensor parameter is greater than 103 kPa.
- If less than the specified range, test the signal circuit pin B for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
If all circuits test normal, test or replace the MAP sensor.