DTC P0654 Engine Speed Output Circuit. Buick LeSabre 2000

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2000 🢒 LeSabre 🢒 DTC 🢒 DTC P0654 Engine Speed Output Circuit

Engine Controls Components
IC Module, CMP and CKP Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

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 18X reference pulse. Once the 18X 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 engine is running.

•	The system voltage is between 9-16 volts.

Conditions for Setting the DTC

The PCM detects an incorrect voltage on the tachometer control circuit.

Diagnostic Aids

Check for the following conditions:

•	A faulty connection at the PCM or instrument cluster--Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Use a corresponding mating terminal to test for proper terminal tension.

•

A 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 tachometer control circuit at the PCM harness connector while moving connectors and wiring harnesses related to the tachometer control circuit. A change in voltage will indicate the location of the fault.

Test Description

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 B+ on the output driver circuit. Either condition would result in a measured current of over 0.5 amps.

Checks for a faulty instrument cluster.

This vehicle is equipped with a PCM that utilizes an electrically erasable programmable read only memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

DTC P0654 - Engine Speed Output Circuit

Step

Action

Values

Yes

Was Instrument Cluster Diagnositic System Check performed?

Go to Step 2

Go to Diagnostic System Check - Instrument Cluster

Was the Powertrain On-Board Diagnostic System Check performed?

Go to Step 3

Go to Powertrain On Board Diagnostic (OBD) System Check

Turn OFF the ignition switch, disconnect the PCM.
Turn ON the ignition switch.
Using a digital multimeter (DMM) , measure the voltage between the tachometer control circuit at the PCM harness connector and ground.

Is the voltage near the specified value?

B+

Go to Step 4

Go to Step 7

Set up the DMM to measure a 10 amp range.
Measure the 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 V

Go to Step 14

Go to Step 6

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

Is the action complete?

Go to Step 16

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:

•	The short to ground in the ignition feed circuit

•	The shorted component--Refer to Wiring Repairs in Wiring Systems.

Replace the fuse.

Is the action complete?

Go to Step 16

Disconnect the instrument cluster.
Turn ON the ignition switch, measure the 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 13

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

Was a problem found?

Go to Step 16

Go to Step 11

Check the tachometer control circuit and the instrument cluster ignition feed circuit for a faulty connection at the instrument cluster or at the PCM.
If a problem is found, replace the faulty terminals.

Was a problem found?

Go to Step 16

Go to Step 14

Check for poor connections at the PCM.
If a problem is found, repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Was a problem found?

Go to Step 16

Go to Step 15

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

Is the action complete?

Go to Step 16

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

Is the action complete?

Go to Step 16

Important: Replacement PCM must be programmed.

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

Is the action complete?

Go to Step 16

Operate the vehicle while observing the IP tachometer.

Does the IP tachometer operate properly?

System OK

Go to Diagnostic System Check - Instrument Cluster