Pinpoint Test G: The Tachometer Is Inoperative

Instrumentation, Message Center and Warning Chimes

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) 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 (Instrument Panel Cluster) does not receive the engine rpm data for 5 seconds or less, the IPC (Instrument Panel Cluster) defaults the tachometer to the last setting, based upon the last known good rpm message. If the IPC (Instrument Panel Cluster) does not receive the engine rpm data from the PCM for more than 5 seconds, the IPC (Instrument Panel Cluster) 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 (Instrument Panel Cluster) for 5 seconds or longer, the IPC (Instrument Panel Cluster) sets DTC U0401:68 and defaults the tachometer to 0 rpm.

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

This pinpoint test is intended to diagnose the following:

- PCM

- IPC (Instrument Panel Cluster)

PINPOINT TEST G : THE TACHOMETER IS INOPERATIVE

G1 RETRIEVE THE RECORDED PCM DTCs FROM THE 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
DIAGNOSE all PCM DTCs first. REFER to Computers and Control Systems Information.

No
GO to G2.

G2 CARRY OUT THE TACHOMETER ACTIVE COMMAND USING THE SCAN TOOL

- Ignition ON.

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

- Select the IPC (Instrument Panel Cluster) tachometer (TACH_IND) active command. Command the tachometer in 10% increments while monitoring the tachometer.

Does the tachometer indication increase within specifications?

Yes
GO to G3.

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

G3 RETRIEVE THE RECORDED DTCs FROM THE IPC (Instrument Panel Cluster) SELF-TEST

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

Are any DTCs recorded?

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

For DTC U0401:68, 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
INSTALL a new PCM. TEST the system for normal operation.