Pinpoint Test G: The Tachometer Is Inoperative

Instrumentation, Message Center and Warning Chimes

Pinpoint Tests


Pinpoint Test G: The Tachometer Is Inoperative

Normal Operation

The PCM uses the Crankshaft Position (CKP) sensor to measure the engine rpm. The PCM sends the Instrument Panel Cluster (IPC) the data over the High Speed Controller Area Network (HS-CAN) communication bus to command the tachometer gauge 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 U0100:87 in continuous memory and defaults the tachometer to 0 rpm. If the engine rpm data is deemed invalid by the IPC for 5 seconds or longer, the IPC sets DTC U0401:68 and defaults the tachometer to 0 rpm.

NOTE: If DTC U0100:87 is set in the IPC, other observable symptoms can be an inoperative speedometer, temperature gauge or odometer.

This pinpoint test is intended to diagnose the following:

- CKP sensor
- IPC



PINPOINT TEST G: THE TACHOMETER IS INOPERATIVE

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G1 RETRIEVE THE RECORDED PCM DTCs FROM THE KOEO SELF-TEST


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

Yes
DIAGNOSE all PCM DTCs first. REFER to Computers and Control Systems Information.

No
GO to G2.

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G2 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 in 10% increments while monitoring the tachometer.
- Does the tachometer begin at 0 rpm, increase to 7,000 rpm then return to 0 rpm?

Yes
GO to G3.

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

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G3 RETRIEVE THE RECORDED DTCs FROM THE IPC SELF-TEST


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

Yes
For DTC U0100:87, GO to Pinpoint Test AQ. Pinpoint Tests AQ: DTC U0100:87

For DTC U0401:68, RETRIEVE and REPAIR all non-network DTCs in the PCM and other modules on the network. REFER to Computers and Control Systems Information and Body Control Systems for a list of all DTCs.

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

No
INSTALL a new PCM. REFER to Computers and Control Systems. TEST the system for normal operation.

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