Coolant Temperature Sensor
- Ensure coolant temperature sensor is properly installed and connector firmly seated. Ensure cooling system is full. Bleed cooling system (if necessary). Check resistance between switch connections (between wire terminal and ground if single wire connector). See COOLANT TEMPERATURE SENSOR RESISTANCE table.
- Resistance should be within specification. If resistance is not within specification, replace sensor. If resistance is correct, check sensor wiring circuit and repair.
NOTE:
On 525i, 535i and 735i models with self-diagnostics, a short or open in the coolant temperature sensor will set a Code 45. If Code 45 is set, MCU will operate engine with preset coolant temperature value of 122°F (50°C).
COOLANT TEMPERATURE SENSOR RESISTANCE
| Coolant Temperature - °F (°C) | Ohms |
|---|---|
| 14 (-10) | 8,200-10,500 |
| 63-73 (17-23) | 2,300-2,700 |
| 171-181 (77-83) | 300-360 |