Pinpoint Test J: Inaccurate Tachometer Indication

Instrumentation, Message Center and Warning Chimes

Pinpoint Test J: Inaccurate Tachometer Indication

Normal Operation

The PCM uses the Crankshaft Position (CKP) sensor to measure the engine rpm. The Instrument Cluster (IC) receives the tachometer data from the PCM over the High Speed Controller Area Network (HS-CAN) communication bus and commands the tachometer according to the data. If the IC (Instrument Cluster) does not receive the engine rpm data or the data received is deemed invalid by the IC (Instrument Cluster) for more than 5 seconds, the IC (Instrument Cluster) sets DTC U0100.

NOTE: If DTC U0100 is set in the IC (Instrument Cluster), other observable symptoms are likely to be an inoperative speedometer, tachometer and temperature gauge.

This pinpoint test is intended to diagnose the following:

- PCM concern

- IC (Instrument Cluster)

PINPOINT TEST J : INACCURATE TACHOMETER INDICATION

J1 RETRIEVE THE RECORDED DTCs FROM THE IC (Instrument Cluster) SELF-TEST

- Check for recorded IC (Instrument Cluster) DTCs from the self-test.

Is DTC U0100 recorded?

Yes
GO to Pinpoint Test AT. Pinpoint Test AT: DTC U0100

For DTC U2023, RETRIEVE and REPAIR all non-network DTCs in the PCM and other modules on the network.

For all other DTCs, REFER to DTC Charts. Instrumentation, Message Center and Warning Chimes

No
GO to J2.

J2 RETRIEVE THE RECORDED DTCs FROM THE PCM KOEO (Key ON Engine OFF) SELF-TEST

- Check for recorded PCM DTCs from the Key ON Engine OFF (KOEO) self-test.

Are any DTCs recorded?

Yes
REFER to Computers and Control Systems Information.

No
GO to J3.

J3 OBSERVE THE TACHOMETER POINTER POSITION

- Start the engine.

- Observe the tachometer while increasing the engine speed between 0 and 2,000 rpm.

- Ignition OFF.

Does the tachometer begin at 0 rpm, increase with engine rpm then return to 0 rpm with the engine off?

Yes
GO to J4.

No
INSTALL a new IC (Instrument Cluster). REFER to Instrument Cluster (IC) . TEST the system for normal operation.

J4 CARRY OUT THE IC (Instrument Cluster) TACHOMETER ACTIVE COMMAND USING THE SCAN TOOL

- Ignition ON.

- Enter the following diagnostic mode on the scan tool: IC (Instrument Cluster) DataLogger.

- Select the IC (Instrument Cluster) tachometer (TACH_IND) active command and scroll in 10% increments.

Does the tachometer start at 0 rpm and increase by 700 rpm for each 10% increase commanded?

Yes
GO to J5.

No
INSTALL a new IC (Instrument Cluster). REFER to Instrument Cluster (IC) . TEST the system for normal operation.

J5 CARRY OUT THE IC (Instrument Cluster) DEALER TEST MODE

- Start the engine.

- Enter the IC (Instrument Cluster) dealer test mode with the Key ON Engine Running (KOER) by pressing and holding the odometer/trip odometer reset button (base cluster) or the message center switch RESET button (message center cluster) while starting the engine. Scroll through the displays until TACHOMETER is displayed.

- Operate the engine at 1,000 rpm, 1,500 rpm and 2,000 rpm.

- Monitor and compare the engine rpm input with the tachometer reading.

Do the self-test engine rpm input values match the tachometer indication?

Yes
GO to J6.

No
INSTALL a new IC (Instrument Cluster). REFER to Instrument Cluster (IC) . TEST the system for normal operation.

J6 CHECK THE PCM RPM SIGNAL INPUT

- Start the engine.

- Enter the following diagnostic mode on the scan tool: PCM DataLogger.

- Monitor the PCM vehicle speed sensor (RPM) PID while operating the engine at 1,000 rpm, 1,500 rpm and 2,000 rpm.

Does the PCM PID match the tachometer indication?

Yes
The tachometer is operating correctly at this time.

No
INSTALL a new IC (Instrument Cluster). REFER to Instrument Cluster (IC) . TEST the system for normal operation.