Coolant heater temperature sensor open circuit or short circuit to 24V
• Check connectors to BMU (E81) B3 and B6 • Check VCA connector on the heater (H32) pin 3 and 4. • Disconnect the VCA connector on the heater (H32) an measure the resistance between pin 4 and pin 2. • If the resistance is measurable (< OL) change the heater (H32). • If the resistance is infinite or OL continue with the following steps. • Check that the wiring harness between BMU (E81) B3 and B6 and heater (H32) pin 3 and 4 via the connector C443 pin 1 and 4 is ok. • Replace BMU (E81)
What you'll see
No driver-visible symptom recorded.
System reaction
The heater in the hybrid battery cooling circuit will not be allowed to start. This may result in degraded hybrid system performance when the ambient temperature is below 5ºC. The battery system will eventually get warm when the vehicle is used even without heater but this may take some time. During this time the hybrid system has degraded performance.
Diagnostic depth
Electrical diagnosis in BMU
• Temperature sensor cables is not connected to BMU. • Temperature sensor cables is not connected to the heater in HRU/HPU. • Temperature sensor cables has shorted to 24V somewhere between BMU and hybrid battery heater. • Temperature sensor cables is broken somewhere between BMU and hybrid battery heater. • The temperature sensor is broken.