Circuit/System Verification
- If the ignition has been OFF for 8 hours or more, the ECT and the IAT, should be within 6°C (11°F) of each other and also the ambient temperature. Turn ON the ignition, with the engine OFF, and use a scan tool to observe the IAT and the ECT sensor parameters. Compare those sensor parameters to each other and also to the ambient temperature. A slight to moderate resistance in the IAT signal or low reference circuit, can widen the spread between the two sensors and cause this DTC to set.
- An IAT sensor that is skewed lower at various ambient temperatures, due to more resistance than is normal, can widen the spread between the two sensors and cause this DTC to set. Measure and record the resistance of the IAT sensor at various ambient temperatures, and then compare those measurements to the Temperature vs Resistance Table. Refer to TEMPERATURE VERSUS RESISTANCE .
- Inspect the ECT sensor terminals for corrosion, and for engine coolant leaking through the sensor.
- Turn OFF the ignition.
- Inspect the cooling system surge tank for the proper engine coolant level. Refer to Cooling System Leak Testing and COOLING SYSTEM DRAINING AND FILLING (LS4 GE 47716 FILL) .
- Inspect the thermostatically-controlled coolant heater, if equipped, for damage or modifications. Test for proper operation of the coolant heater. Refer to COOLANT HEATER INOPERATIVE .
CAUTION:
Under pressure, the temperature of the solution in the radiator can be considerably higher, without boiling. Removing the radiator cap while the engine is hot (pressure is high), will cause the solution to boil instantaneously, with explosive force. The solution will spew out over the engine, fenders, and the person removing the cap. Serious bodily injury may result. Flammable antifreeze, such as alcohol, is not recommended for use at any time. Flammable antifreeze could cause a serious fire.