DTC P0608. GMC Truck GMC C-Series Medium Duty Truck B7 2002

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C-Series Medium Duty Truck B7 🢒 DTC 🢒 DTC P0608

Circuit Description

The PCM creates the vehicle speed signal by pulsing the vehicle speed signal circuit to ground. The PCM monitors the voltage on the vehicle speed signal circuit. If the PCM determines that the voltage is out of the normal operating range, a DTC sets.

Conditions for Running the DTC

•	The engine speed is greater than 400 RPM.

•	The ignition voltage is between 6 volts and 18 volts.

Conditions for Setting the DTC

•	The PCM detects that the commanded state of the driver and the actual state of the signal circuit do not match.

•	The condition must be present for a minimum of 5 seconds.

Action Taken When the DTC Sets

•	The PCM stores the DTC information in memory when the diagnostic runs and fails.

•	The PCM records the operating conditions at the time the diagnostic fails. The PCM displays the failure information in the Failure Records on the scan tool.

Conditions for Clearing the DTC

•	The history DTC clears after 40 malfunction free warm-up cycles.

•	The DTC becomes history when the conditions for setting the DTC are no longer present.

•	The PCM receives the clear code command from the scan tool.

Step	Action	Values	Yes	No
Schematic Reference: Instrument Cluster Schematics
1	Did you perform the Instrument Cluster Diagnostic System Check?	--	Go to Step 2	Go to Diagnostic System Check - Instrument Cluster
2	Install a scan tool. Raise the vehicle's drive wheels. Refer to Lifting and Jacking the Vehicle in General Information. Start the engine. Place the transmission into drive for an automatic transmission or third gear for a manual transmission. With the scan tool, observe the Vehicle Speed Sensor parameter in the PCM Engine Data 1 data list. Does the Vehicle Speed Sensor parameter match the speedometer display?	--	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Turn the ignition OFF. Disconnect C2 at the PCM. 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?	9.0 V	Go to Step 4	Go to Step 5
4	Test the vehicle speed signal circuit for a short to battery voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 10	Go to Step 6
5	Test the vehicle speed signal circuit for a short to ground or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 10	Go to Step 7
6	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 10	Go to Step 8
7	Inspect for poor connections at the harness connector of the IPC. 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 10	Go to Step 9
8	Important:: Program the replacement PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 8.1L. Did you complete the replacement?	--	Go to Step 10	--
9	Replace the IPC. Refer to Instrument Cluster Replacement . Did you complete the replacement?	--	Go to Step 10	--
10	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