Pinpoint Test C: The Tachometer Is Inoperative

Instrumentation, Message Center and Warning Chimes

Pinpoint Test C: The Tachometer Is Inoperative

Normal Operation

The PCM uses the Crankshaft Position (CKP) sensor to measure the engine rpm. The PCM sends the data to the Instrument Panel Cluster (IPC) over the High Speed Controller Area Network (HS-CAN) communication bus to command the tachometer according to the data.

If the engine rpm data is invalid for 5 seconds or less or if the IPC does not receive the engine rpm data for 5 seconds or less, the IPC defaults the tachometer to the last setting, based upon the last known good rpm message.

If the IPC does not receive the engine rpm data from the PCM for more than 5 seconds, the IPC sets DTC U0100:00 in continuous memory and defaults the tachometer to 0 rpm. If the engine rpm data received is deemed invalid by the IPC for 5 seconds or more, the IPC sets DTC U0401:68 and defaults the tachometer to 0 rpm.

NOTE: If DTC U0100:00 sets in the IPC, other observable symptoms may be an inoperative speedometer or odometer.

This pinpoint test is intended to diagnose the following:

- PCM
- IPC

PINPOINT TEST C: THE TACHOMETER IS INOPERATIVE

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C1 RETRIEVE THE RECORDED DTCs FROM THE PCM KOEO SELF-TEST

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

Yes
REFER to Computers and Control Systems.

No
GO to C2.

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C2 RETRIEVE THE RECORDED DTCs FROM THE IPC SELF-TEST

- Check for recorded IPC DTCs from the self-test.
- Are any DTCs recorded?

Yes
For DTC U0100:00, GO to Pinpoint Test AM. Pinpoint Tests AM: DTC U0100:00 and P1607:87

For all other DTCs, REFER to DTC Charts.

No
GO to C3.

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C3 CARRY OUT THE TACHOMETER ACTIVE COMMAND USING THE SCAN TOOL

- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IPC DataLogger.
- Select the IPC tachometer (TACH_IND) active command. Command the tachometer on then off while monitoring the tachometer.
- Does the tachometer begin at 0 rpm, increase to 7,000 rpm then return to 0 rpm?

Yes
INSTALL a new PCM. REFER to Electronic Engine Controls Service and Repair. TEST the system for normal operation.

No
INSTALL a new IPC. REFER to Instrument Panel Cluster (IPC) Service and Repair. TEST the system for normal operation.

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