DTC P0654 Engine Speed Output Circuit. Chevrolet Malibu 1999

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1999 🢒 Malibu 🢒 Engine 🢒 Engine Controls - 3.1L 🢒 DTC P0654 Engine Speed Output Circuit

Circuit Description

The PCM supplies the ground to energize the Instrument Cluster tachometer. When the ignition switch is first turned on the PCM grounds the tachometer circuit. The circuit will remain grounded until the PCM receives the first 24X reference pulse. Once the 24X reference pulse is received, the PCM controls the pulse frequency in relationship to engine RPM. The tachometer is controlled at a rate of two pulses per crankshaft revolution.

Conditions for Running the DTC

The ignition is on.

Conditions for Setting the DTC

•	An improper voltage level has been detected on the Tachometer Output Control circuit.

•	The above condition present for at least 30 seconds.

Diagnostic Aids

Check for the following conditions:

•

Poor connection at the PCM. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Intermittents and Poor Connections Diagnosis , Connector Repairs and Wiring Repairs in Wiring Systems.

•

Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the PCM, turn the ignition on and observe voltmeter connected to the MIL circuit at the PCM harness connector while moving connectors and wiring harnesses related to the MIL control circuit. A change in voltage will indicate the location of the fault. Refer to Intermittents and Poor Connections Diagnosis , Connector Repairs and Wiring Repairs in Wiring Systems.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description

The numbers below refer to the step numbers on the diagnostic table:

Normally, ignition feed voltage should be present on the output driver circuit with the PCM disconnected and the ignition turned ON.

Checks for a shorted component or a short to battery positive voltage ON the output driver circuit. Either condition would result in a measured current of over 0.5 amps.

Checks for a faulty instrument cluster.

A fault in the 24X Crankshaft/Camshaft position sensors feed or ground circuits will result in the loss of both PCM input pulses. Without a 24X reference pulse the PCM can not begin tachometer pulse control causing an inoperative tachometer.

This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to PCM Replacement and Programming Procedures in Powertrain Control Module (PCM) and Sensors.

DTC P0654 - Engine Speed Output Circuit

Step

Action

Values

Yes

Was Diagnostic System Check - Instrument Cluster performed?

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

Was the Powertrain OBD System Check performed?

Go to Step 3

Go to Powertrain On Board Diagnostic (OBD) System Check

Turn OFF the ignition, disconnect the PCM.
Turn ON the ignition.
Using DMM, measure voltage between the tachometer control circuit at the PCM harness connector and ground.

Is voltage near the specified value?

B+

Go to Step 4

Go to Step 7

Set up DMM to measure 10 amp range.
Measure current between the tachometer control circuit and ground.
Monitor the current reading on the DMM for at least 2 minutes.

Does the current reading remain less than the specified value?

0.5 amp

Go to Step 12

Go to Step 5

Disconnect the instrument cluster (leave the PCM disconnected).
Using DMM, measure voltage between the tachometer control circuit and ground.

Is the voltage at the specified value?

0.0.0V

Go to Step 17

Go to Step 6

Locate and repair short to voltage in the tachometer control circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 19

Check the ignition feed fuse for the instrument cluster.

Is the fuse blown?

Go to Step 8

Go to Step 9

Locate and repair the following short condition:

•	Short to ground in ignition feed circuit.

•	Shorted component. Refer to Power and Grounding Component Views in Wiring Systems.

Replace the fuse.

Is the action complete?

Go to Step 19

Disconnect the instrument cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Console and Gauges.
Turn ON the ignition , measure voltage between the ignition feed circuit for the instrument cluster and ground.

Is the voltage near the specified value?

B+

Go to Step 10

Go to Step 16

Check the tachometer control circuit for an open or a short to ground.
If a problem is found, repair the tachometer control circuit. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

Go to Step 19

Go to Step 11

Check the tachometer control circuit and the ignition feed circuit for a poor connection at the instrument cluster and at the PCM.
If a problem is found, replace faulty terminals. Refer to Intermittents and Poor Connections Diagnosis , Connector Repairs , and Repairing Connector Terminals in Wiring Systems.

Was a problem found?

Go to Step 19

Go to Step 17

Turn OFF the ignition , reconnect the PCM and disconnect the instrument cluster.
Connect a test lamp between the tachometer control circuit and the tachometer feed circuit at the instrument cluster harness connector.
With the engine idling, observe the test lamp.

Does the test lamp flash ON and OFF?

Go to Diagnostic Aids

Go to Step 13

Is the test lamp ON steady?

Go to Step 14

Go to Step 15

Locate and repair the following circuit condition:

•	Short to ground in the 24X Crankshaft/Camshaft position sensor feed circuit.

•	Open in the 24X Crankshaft/Camshaft position sensor ground circuit.

•	Faulty splice connection in the 24X Crankshaft/Camshaft position sensor feed or ground circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 19

Check the tachometer control circuit for a poor connection at the PCM.
If a problem is found, replace faulty terminal. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs in Wiring Systems.

Was a problem found?

Go to Step 19

Go to Step 18

Locate and repair open in ignition feed circuit to the instrument cluster. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 19

Replace the instrument cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console.

Is the action complete?

Go to Step 19

Important: Replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

Go to Step 19

Operate the vehicle while observing the I/P tachometer.

Does the I/P tachometer operate properly?

System OK

Go to Diagnostic System Check - Instrument Cluster in Instrument Panel, Console and Gauges