DTC P0128

Issue Description

The P0128 DTC in Dodge vehicles means that the engine coolant temperature is not rising as expected. This typically points to a thermostat that is stuck open, causing the engine to run cooler than optimal.

Dodge P0128 Error Code

Causes

  • Stuck open thermostat.
  • Faulty Engine Coolant Temperature (ECT) sensor.
  • Low coolant level.
  • Wiring or connector issues in the ECT sensor circuit.
  • Faulty radiator fan relay (rare).

Symptoms

  • Check Engine Light (CEL) is On.
  • Poor fuel economy.
  • Engine takes longer to warm up.
  • Heater may blow lukewarm air.
  • Possible emissions test failure.

Solutions

  • Replace faulty or stuck-open thermostat.
  • Test and replace ECT sensor if readings are inaccurate.
  • Top off or flush coolant system if low or dirty.
  • Inspect wiring and connectors for damage.
  • Clear the code and retest after repairs.

Dodge Error Codes

  • DTC P0121

    DTC P0121

    Throttle/Pedal Position Sensor A Range/Performance Problem

  • DTC P0128

    DTC P0128

    Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

  • DTC P0171 & P0174

    DTC P0171 & P0174

    Indicate issues related to the air-fuel mixture.

  • DTC P0301-P0308

    DTC P0301-P0308

    Individual cylinder misfires that caused by issues like a bad spark plug or coil, can also point to mechanical or fuel-related problems.