Fault Code 12
Fault Code 12Ambient Temperature Sensor
- Sensor, harness or Air Conditioning Control Module (A/CCM) open circuit.
- Sensor, harness or A/CCM short circuit to ground.
If the signal on pin 27 (12-way connector, A/CCM) remains at less than 1 volt, suspect either a short circuit to ground on the signal wire or an open circuit on the 5 volt supply to the sensor. If the signal on pin 27 rises to approximately 5 volts, suspect an open circuit on the earth supply to the sensor.
Check the voltage, against the graph below (Image), measured between pin 27 (12-way connector) and pin 19 (22-way connector) A/CCM.
Characteristics Of Ambient Temperature Sensor, Fig.1:
If the voltage is within the set limits, the system is operating correctly.
A resistance check can be carried out on the sensor and should conform with the figures below, measured between pin 27 (12-way connector) and pin 19 (22-way connector) A/CCM.
10 °C 3.1 - 3.7 K Ohm
25 °C 1.6 - 1.8 K Ohm
50 °C 0.5 - 0.7 K Ohm
If the resistance is outside the set limits, renew the sensor.
NOTE: The resistance should continue to decrease as the temperature increases and vice versa.
Inspect sensor harness for open circuit or short circuit to ground. repair as necessary.
If the voltage is outside the set limits, renew the A/CCM.