Fail Safe Cooling
The vehicle has a strategy built into the powertrain control module (PCM) that will control the engine if it starts to overheat.
Stage 1 of the strategy will commence if the engine starts to overheat. The cylinder head temperature (CHT) sensor transmits a signal to the PCM, which then moves the temperature gauge pointer into the red zone.
If the engine is not switched off and the temperature continues to rise, the Powertrain Check Lamp is illuminated. This indicates to the driver that the engine is approaching critical limits and should be stopped. At this point DTC P1285 is set in the PCM which can be retrieved using a scan tool.
Stage 2 of the strategy will commence if the lamp and temperature gauge are ignored by the driver. The PCM will start to control the engine by cutting out two cylinders and restricting the RPM to below 3,000 RPM. Simultaneously the malfunction indicator lamp (MIL) will be illuminated. This indicates that long term engine damage can occur and vehicle emissions will be affected. At this point DTC P1299 is set in the PCM which can be retrieved using a scan tool.
Air is then drawn into the deactivated cylinders. This helps to control the temperature of the engine internal components. The deactivated cylinders are alternated to allow even cooling of all the cylinders.
NOTE: If the driver is using a high percentage of throttle travel (for example, an overtaking maneuver) when the PCM starts engine deactivation (Stage 2), the deactivation will be delayed for 10 seconds.
NOTE: After 2-cylinder operation has begun, the engine will not revert to 4-cylinder operation, even if the temperature should fall, until the ignition is switched off and then on again.
NOTE: The malfunction indicator lamp can only be extinguished by using a diagnostic tool after the fault has been rectified and the DTC cleared.
Stage 3 of the strategy will commence if the engine temperature still continues to rise. This will result in the engine being totally disabled before major engine damage or seizure occurs. The Powertrain Check Lamp will begin to flash, indicating to the driver that the engine will be switched off after 30 seconds. This allows the driver time to choose a suitable parking place.
Saturday, July 25th, 2015 AT 7:53 PM