Test B: DTC B1255 or DTC B1257 - Ambient Temperature Sensor Open Circuit or Short to Ground

PINPOINT TEST B: DTC B1255 OR DTC B1257 - AMBIENT TEMPERATURE SENSOR OPEN CIRCUIT OR SHORT TO GROUND

B1-B2:

B3-B5:

B5-B7:

Normal Operation
Under normal operation, the ambient air temperature sensor receives a ground from the electronic automatic temperature control (EATC) module through circuit RH111 (GY/BU). A 5-volt reference voltage is supplied to the ambient air temperature sensor from the EATC module through circuit VH407 (YE/GN).

Possible Causes
- An open in circuit RH111 (GY/BU) or VH407 (YE/GN)
- A short to ground in circuit VH407 (YE/GN)
- A short together in circuit RH111 (GY/BU) and VH407 (YE/GN)
- Ambient air temperature sensor
- EATC module