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Home >> Jeep >> 2014 >> Wrangler Sahara, Standard Trans >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> 3.6L - DTCS P000A To P0155 >> Diagnosis And Testing >> 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 SENSOR GROUND CIRCUIT
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Refer to  PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE  .