Code 120, A/C Low Temperature Sensor

Code will set if outside air temperature sensor failure is not indicated by HVAC controller, outside air temperature is 4-99°C and A/C low side temperature sensor indicates less than -37°C or greater than 99°C.

1. Determines if conditions to set code are present.
2. If scan indicates A/C low side temperature is greater than 99°C with A/C low sensor disconnected and terminals "A" and "B" jumpered, A/C low temperature sensor circuits are okay.
3. If scan indicates A/C low side temperature less than -35°C with sensor unplugged, sensor is faulty.
4. When A/C low temperature sensor input circuit is jumpered to ground, scan should display temperature is greater than 99°C.
5. When backprobing PCM A/C low temperature sensor input terminal to ground, scan should display A/C low side temperature greater than 99°C.

Fig 1: Code 120 Schematic (4.0L) A/C Low Temperature Sensor

Fig 2: Code 120 Diagnostic Flow Chart (4.0L) A/C Low Temperature Sensor