Coolant temperature sensor open circuit or short circuit to 24V
• Check connectors to BMU (E81) B9 and B12 • For FPC1(B) - Check wiring between BMU and water temperature sensor and harness connector C443 pin 11 and 12 - Disconnect the connector C443 and the BMU E81 connectors (A, B and C) and measure the resistance between pin 11 and pin 14 and between pin 11 and pin 15 on the HRU side of the connector C443. - If the resistance is measureble(< OL) in any case change the sensor T179 including harness. - Measure the resistance between pin 11 and pin 14 and between pin 11 and pin 15 on the BMU side of the connector C443. - If the resistance is measureble(< OL) in any case replace the harness between C443 and BMU - If the resistance is infinite or OL in any case, change the BMU(E81) • For FPC1(A) - Check wiring between BMU and water temperature sensor T179. - Disconnect the connector E81A and B and measure the resistance between pin B9 and pin A2 in the harness connector. - If the resistance is measureble(< OL) change the sensor T179 - If the resistance is infinite or OL, change the 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 C443 (FPC1(B) only) • Temperature sensor cables has shorted to 24V somewhere between BMU and water temperature sensor. • Temperature sensor cables is broken somewhere between BMU and water temperature sensor. • The water temperature sensor is broken.