OBD Code P2189 on 2004 Audi A4 1.8T: Coolant Temperature Sensor Issue and No Heat Symptoms
I own a 2004 Audi A4 1.8T and am experiencing persistent engine light illumination despite replacing both coolant temperature sensors. The radiator fan activates when the engine is cold, but I still do not receive adequate heat from the heater core. Approximately one year ago, I replaced the thermostat and flushed the heater core, yet the issue persists. Given that the vehicle shows no significant overheating and the temperature gauge reads steadily around 200°F after driving for 15–20 minutes, I suspect a deeper issue with sensor readings or engine control signal integrity.
OBD Code P2181 refers to the Coolant Temperature Sensor (G62), located at the rear of the cylinder head. Since you've already replaced both sensors, it's advisable to consult a VW-certified mechanic to inspect wiring connections and verify signal integrity from the Engine Control Module (ECM). Faulty wiring or incorrect resistance values in the sensor circuit can still trigger this code even after replacement.