Pinpoint Tests AH: The Engine Over-Temperature Message Center Warning Indicator Is Never/Always On
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test AH: The Engine Over-Temperature Message Center Warning Indicator Is Never/Always On
Normal Operation
The PCM uses the Cylinder Head Temperature (CHT) sensor (gasoline) or Engine Coolant Temperature (ECT) sensor (diesel) to measure the engine coolant temperature. The Instrument Panel Cluster (IPC) receives the engine coolant temperature data from the PCM over the High Speed Controller Area Network (HS-CAN) communication bus. The PCM monitors the engine coolant temperature and when an over-temperature condition exists, the PCM sends a command to the IPC to send the temperature gauge to the hot band and to turn on the engine over-temperature message center warning indicator.
Failsafe Cooling
On gasoline engines, the PCM provides a failsafe cooling mode, which provides a visual indication to the driver that the engine is overheating while reducing the engine power to lower the engine temperature. When the PCM sends the IPC a failsafe mode command, the IPC turns on the engine over-temperature message center warning indicator.
If the engine coolant temperature or failsafe messages are missing or invalid for 5 seconds or less, the IPC defaults the engine over-temperature message center warning indicator to the last on/off setting, based upon the last known good temperature or failsafe cooling messages.
If the engine coolant temperature or failsafe messages are missing for more than 5 seconds, the IPC sets DTC U0100:00 in continuous memory and defaults the engine over-temperature message center warning indicator on.
If the engine coolant temperature data is deemed invalid by the IPC, the IPC sets DTC U0401:86 and defaults the engine over-temperature message center warning indicator on.
NOTE: If DTC U0100:00 is set in the IPC, other observable symptoms may be an inoperative tachometer, temperature gauge or odometer.
This pinpoint test is intended to diagnose the following:
- Engine over-temperature concern
- IPC
PINPOINT TEST AH: THE ENGINE OVER-TEMPERATURE MESSAGE CENTER WARNING INDICATOR IS NEVER/ALWAYS ON
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AH1 RETRIEVE THE RECORDED DTCs FROM THE IPC SELF-TEST
- Check for recorded IPC DTCs from the self-test.
- Is DTC U0100:00 recorded?
Yes
GO to Pinpoint Test AV. Pinpoint Tests AV: DTC U0100:00
No
GO to AH2.
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AH2 VERIFY THE OPERATION OF THE POWERTRAIN MALFUNCTION (WRENCH) MESSAGE CENTER INDICATOR
- Ignition OFF.
- Disconnect: In-Line C219.
- Ignition ON.
- NOTE: If multiple warnings are present, the message center indicators rotate through each of the warnings. Allow the displays to rotate through each display while determining whether the powertrain malfunction (wrench) and over-temperature message center indicators are active.
- Observe the message center or integrated display area of the IPC with the PCM connected and disconnected.
- Does the powertrain malfunction (wrench) indicator remain off when the PCM is connected and become active with the PCM disconnected?
Yes
VERIFY that the temperature gauge is displaying in the hot band.
If the temperature gauge is displaying in the hot band, REFER to Cooling System &/or Engine Block Heater to diagnose the engine overheating condition.
No
INSTALL a new IPC. REFER to Instrument Panel Cluster (IPC) Instrument Panel Cluster (IPC). TEST the system for normal operation.
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