Pinpoint Test C: The Temperature Gauge Is Inoperative
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test C: The Temperature Gauge Is Inoperative
Normal Operation
The PCM uses the Cylinder Head Temperature (CHT) sensor to measure the Engine Coolant Temperature (ECT). The Instrument Cluster (IC) receives the ECT data from the PCM over the High Speed Controller Area Network (HS-CAN) communication bus. The IC monitors the ECT 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 IC to illuminate the engine over-temperature warning indicator and send the temperature gauge to the full hot (H) position.
If the ECT data is missing or invalid for 5 seconds or less, the IC defaults the temperature gauge to the last setting, based upon the last known good temperature status message. If the IC does not receive the ECT status message from the PCM for more than 5 seconds, the IC sets DTC U0101 in continuous memory and defaults the temperature gauge to cold (C). If the ECT status message is invalid for more than 5 seconds, the IC sets DTC U2023 in continuous memory and defaults the temperature gauge to cold (C).
NOTE: If DTC U0101 is set in the IC, other observable symptoms may be an inoperative tachometer, speedometer or odometer.
This pinpoint test is intended to diagnose the following:
- PCM
- IC
PINPOINT TEST C: THE TEMPERATURE GAUGE 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 the Computers and Control Systems Information.
No
GO to C2.
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C2 RETRIEVE THE RECORDED DTCs FROM THE IC SELF-TEST
- Check for recorded IC DTCs from the self-test.
- Are any DTCs recorded?
Yes
For DTC U0101, Go To Pinpoint Test AF. Pinpoint Tests AF: DTC U0101
For all other DTCs, REFER to DTC Charts. Instrumentation, Message Center and Warning Chimes
No
GO to C3.
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C3 CARRY OUT THE TEMPERATURE GAUGE ACTIVE COMMAND USING THE SCAN TOOL
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: IC DataLogger.
- Select the IC temperature gauge (ECT_GAUGE) active command. Command the temperature gauge to the approximate values in the following table while monitoring the gauge.
- Does the temperature gauge begin to move in the cold (C) range, move to approximately mid-range and then full hot (H)?
Yes
INSTALL a new PCM. TEST the system for normal operation.
No
INSTALL a new IC. REFER to Instrument Cluster (IC) Instrument Cluster (IC). TEST the system for normal operation.
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