GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The hot lamp/low coolant lamp on the instrument panel has the ability to illuminate as a result of engine (DTC P0127) or transaxle (DTC P0218) overheating. The lamp will come on and stay on steady for either of these conditions. If the PCM detects a low coolant condition (DTC P1620), the lamp will flash as opposed to a solid ON lamp.

Conditions for Setting the DTC

Important: The hot lamp/low coolant lamp on the instrument panel will illuminate when these DTCs are set. The lamp will remain ON steady and is shared by both engine coolant and transaxle temperature circuits.

DTC P0217 will set if:

    • The engine coolant is above 118°C (244°F).
    • No other ECT sensor DTCs are set.

DTC P0218 will set if:

    • The transaxle fluid temperature is above 140°C (284°F).
    • The actuator temperature is above 160°C (320°F) as calculated by the PCM from fluid temperature and actuator on time.
    • No other transaxle temperature sensor DTCs are set.

Diagnostic Aids

Important: The A/C will turn OFF at 118°C (244°F) to protect the engine and transaxle.

    • If the lamp is flashing, refer to DTC P1620 diagnostics.
    • Overload due to trailer towing
    • Transaxle oil cooler restricted
    • Transaxle oil cooler lines restricted
    • Radiator or condenser air flow restricted
    • Front air dam missing and/or damaged
    • Low transaxle fluid level
    • Inoperative cooling fan
    • Corrosion at ECT sensor connectors
    • Engine cooling system components water pump and/or thermostat
    • ECT resistance malfunction -- Refer to ECT Out of Range - High