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Home >> Jeep >> 2008 >> Commander Overland, RWD >> Repair and Diagnosis >> Engine Performance >> System >> DTCS P0128 To P0197 >> P0128-Thermostat Rationality >> Possible Causes

Possible Causes

Possible Causes 
LOW COOLANT LEVEL
THERMOSTAT OPERATION
SIGNAL CIRCUIT SHORTED TO VOLTAGE
TEMPERATURE SENSOR
SIGNAL CIRCUIT OPEN
SENSOR GROUND CIRCUIT OPEN
SIGNAL CIRCUIT SHORTED TO GROUND
SIGNAL CIRCUIT SHORTED TO THE (K900), (G931) SENSOR GROUND CIRCUIT
OTHER POSSIBLE CAUSES
POWERTRAIN CONTROL MODULE (PCM)

Always perform the PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE before proceeding.