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Home >> Chrysler >> 2009 >> 300 Signature Series >> Repair and Diagnosis >> External Pages >> Different car >> Section 49 (Engine Controls - DTCS P0122 To P0175) >> Diagnosis And Testing >> P0128-Thermostat Rationality >> Possible Causes

Possible Causes

WARNING: This page is about a different car, the 2006 Dodge Magnum, 2006 Dodge Charger, and 2006 Chrysler 300. However, it is still accessible from the selected car via links, so may be relevant.
Possible Causes 
LOW COOLANT LEVEL
THERMOSTAT OPERATION
SIGNAL CIRCUIT SHORTED TO BATTERY VOLTAGE
TEMPERATURE SENSOR
SIGNAL CIRCUIT OPEN
(K900) SENSOR GROUND CIRCUIT OPEN
SIGNAL CIRCUIT SHORTED TO GROUND
SIGNAL CIRCUIT SHORTED TO (K900), (G931) SENSOR GROUND
OTHER POSSIBLE CAUSES
PCM

Always perform the  PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE  before proceeding.