The ECM controls cooling fan speed (low,medium, high) based on engine coolant temperature, vehicle speed, and A/C switch position. Fans will default to high-speed operation upon ECT or VSS failure.
ECM sets DTC P1624 if the ECM detects that the fan relay control line is open, short to ground or battery.
Item
Detecting Condition
Possible Cause
DTC Strategy
? Driver stage check
? Contact resistance in connectors
? Open or short circuit
? Malfunctioning fan relay
Enable Conditions
? Battery voltage > 10V
Threshold Value
? Open or short to ground
? Short to battery
Diagnostic Time
? 10 seconds