Test D: Incorrect Temperature Gauge Indication

PINPOINT TEST D: INCORRECT TEMPERATURE GAUGE INDICATION

Normal Operation
The PCM uses the cylinder head temperature (CHT) sensor to measure the engine coolant temperature. The instrument cluster (IC) receives the engine coolant temperature data from the PCM over the high speed controller area network (HS-CAN) communication bus. The instrument cluster (IC) monitors the engine coolant temperature data received from the PCM and commands the temperature gauge indication with a corresponding movement of the pointer.

The PCM incorporates 2 strategies for failsafe cooling in the event that the engine has reached an over temperature condition in order to protect the engine from severe damage. The first strategy is when the PCM provides engine operation but takes on the limp home strategy. The second strategy is when the PCM determines that the engine is sufficiently over temperature and is about to be shut down by the PCM. In both strategies, the PCM provides the engine over temperature information to the instrument cluster (IC) to illuminate the engine over temperature warning indicator and send the temperature gauge to the full hot (H) position.

If the engine coolant temperature data is missing or invalid for 5 seconds or less, the instrument cluster (IC) defaults the temperature gauge to the last setting, based upon the last known good temperature status message. If the instrument cluster (IC) does not receive the engine coolant temperature status message from the PCM for more than 5 seconds, the instrument cluster (IC) sets DTC U0101 in continuous memory and defaults the temperature gauge to cold (C). If the engine coolant temperature status message is invalid for more than 5 seconds, the instrument cluster (IC) sets DTC U2023 in continuous memory and defaults the temperature gauge to cold (C).

NOTE: If DTC U0101 is set in the instrument cluster (IC), other observable symptoms may be an inoperative tachometer, speedometer or odometer.

This pinpoint test is intended to diagnose the following:
- CHT sensor
- PCM
- Instrument cluster (IC)

D1-D4:

D4-D7:

D8: