Diagnostic Aids

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

If any additional powertrain DTCs are stored, refer to Diagnostic Trouble Code (DTC) List in Engine Controls-3.8 L (L26 and L32).
For intermittent diagnosis, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

DTC P0608

Step	Action	Value(s)	Yes	No
Schematic Reference: Cruise Control Schematics Connector End View Reference: Cruise Control Connector End Views or Powertrain Control Module (PCM) Connector End Views in Engine Controls 3.8 L (L26 and L32)
1	Did you perform the Cruise Control Diagnostic System Check?	-	Go to Step 2	Go to Diagnostic System Check - Cruise Control
2	Turn the ignition OFF. Install a scan tool. Raise the vehicle drive wheels. Refer to Lifting and Jacking the Vehicle in General Information. Start the engine. Place the transmission into drive. With a scan tool, observe the Vehicle Speed Sensor parameter in the PCM Cruise Control Data list. Does the Vehicle Speed Sensor parameter indicate any vehicle speed?	-	Go to Step 4	Go to Step 3
3	Is DTC P0502 or P0503 current in the PCM?	-	Go to Diagnostic Aids	Go to Step 7
4	Turn the ignition OFF. Disconnect the throttle actuator control (TAC) module. Turn the ignition ON, with the engine OFF. Measure the voltage from the vehicle speed signal circuit to a good ground. Does the voltage measure greater than the specified value?	8.5 V	Go to Step 5	Go to Step 6
5	Test the vehicle speed signal circuit for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 11	Go to Step 8
6	Test the vehicle speed signal circuit for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 11	Go to Step 7
7	Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 11	Go to Step 9
8	Inspect for poor connections at the harness connector of the throttle actuator control (TAC) module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 11	Go to Step 10
9	IMPORTANT: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 3.8 L (L26 and L32).Did you complete the replacement?	-	Go to Step 11	-
10	Replace the TAC module. Refer to Throttle Body Assembly Replacement (L26)Throttle Body Assembly Replacement (L32) in Engine Controls - 3.8 L (L26 and L32). Did you complete the replacement?	-	Go to Step 11	-
11	Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC. Does the DTC reset?	-	Go to Step 2	System OK