DTC P0654. GMC Truck GMC T-Series Medium Duty Truck F6/F7/F8 2004

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC T-Series Medium Duty Truck F6/F7/F8 🢒 DTC 🢒 DTC P0654

Circuit Description

The engine control module (ECM) creates the engine speed signal by pulsing the signal circuit to ground at the rate of 2 pulses per engine revolution. The instrument panel cluster (IPC) converts the signal to a tachometer position. The IPC also receives a class 2 message from the ECM indicating the engine speed. The IPC uses this class 2 message for diagnostic purposes.

Conditions for Running the DTC

•	The IPC receives a class 2 message from the ECM indicating that the engine speed is greater than 800 RPM.

•	The ignition voltage is between 9 volts and 18 volts.

Conditions for Setting the DTC

•	The IPC does not detect a 2 pulses per engine revolution signal on the engine speed signal circuit.

•	The above condition is present for at least 5 seconds.

Action Taken When the DTC Sets

The IPC stores a DTC B0560 in memory.

Conditions for Clearing the DTC

•	A history DTC clears after 100 malfunction free warm-up cycles.

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

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

Step

Action

Values

Yes

Schematic Reference: Instrument Cluster Schematics

Did you perform the Instrument Cluster Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

Install a scan tool.
Start the engine.
With the scan tool, observe the Engine Speed parameter in the ECM Engine Data 1 data list.

Does the Engine Speed parameter match the tachometer display?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

Turn the ignition OFF.
Disconnect the following engine control module (ECM) connectors:

•	C2:w/o CTF

•

C1:CTF

Turn the ignition ON, with the engine OFF.
Measure the voltage from the engine speed signal circuit of the ECM to a good ground.

Does the voltage measure greater than the specified value?

9 V

Go to Step 4

Go to Step 5

Test the engine speed signal circuit for a 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 10

Go to Step 6

Test the engine speed signal circuit for a for an open or 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 10

Go to Step 7

Inspect for poor connections at the harness connector of the ECM. 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

Inspect for poor connections at the harness connector of the instrument panel cluster (IPC). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring System.

Did you find and correct the condition?

Go to Step 10

Go to Step 9

Important: Program the replacement ECM.

Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data in Engine Controls - 7.8L.

Did you complete the replacement?

Go to Step 10

Important: Program the replacement IPC.

Replace the IPC. Refer to Instrument Cluster Replacement .

Did you complete the replacement?

Go to Step 10

Use the scan tool in order to clear the DTCs.
Operate vehicle within the Conditions for Running this DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK