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.
- 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 harness connector at the throttle body. Allow up to 2 minutes for the ECM to completely power down.
- Ignition OFF, test for less than 5 ohms between the low reference circuit terminal C and ground.
- If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
- Ignition ON, test for 4.8-5.2 volts between 5-volt reference circuit terminal E and ground.
- If less than 4.8 volts, test 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
- If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- Verify the scan tool TP sensor 1 voltage is less than 0.1 volt.
- If greater than 0.1 volt, test the signal circuit terminal D for a short to voltage. If the circuit tests normal, replace the ECM.
- Verify the scan tool TP sensor 2 voltage is greater than 4.8 volts.
- If less than 4.8 volts, test the signal circuit terminal F for a short to ground. If the circuit tests normal, replace the ECM.
- Install a 3A fused jumper wire between the signal circuit terminal D and the 5-volt reference circuit terminal E of the TP sensor 1. Verify the TP sensor 1 voltage is greater than 4.8 volts.
- If less than 4.8 volts, test the TP sensor 1 signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
- Install a 3A fused jumper wire between the signal circuit terminal F and the low reference circuit terminal C of the TP sensor 2. Verify that the TP sensor 2 voltage is less than 0.1 volt.
- If greater than 1.0 volt, test the TP sensor 2 signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
- Ignition OFF, disconnect the harness connector at the ECM.
- Test for less than 5 ohms on all TP sensor circuits between the following terminals:
- ECM X2 signal circuit terminal 64 to TP terminal D
- ECM X2 signal circuit terminal 66 to TP terminal F
- ECM X2 5-volt reference circuit terminal 44 to terminal E
- If greater than 5 ohms, repair the affected circuit for open/high resistance.
- Test for infinite resistance between TP sensor 1 signal circuit terminal D and TP sensor signal circuit terminal F.
- If less than infinite resistance, repair the short between TP sensor 1 signal circuit and TP sensor 2 signal circuit.
- If all circuits test normal, replace the throttle body.