What it means
The ECM detects a low fault on the a/c compressor control module internal temperature sensor a circuit. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Internal temperature sensor A in the A/C compressor control module helps the module monitor its temperature and manage compressor operation. This code sets when sensor A's circuit reads lower than the module can reliably use, which can result from a signal short to ground or a shorted sensor.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- Connector pins corroded - high contact resistance
Symptoms
- A/C warning light may come on
- Air conditioning may provide little or no cooling
- A/C operation may be limited or disabled
How to diagnose it
- Record freeze-frame data and check live data for sensor A's reported temperature, noting whether the low reading is steady or appeared under a particular operating condition.
- Inspect sensor A's connector and wiring for corrosion, damaged insulation, loose pins, or a signal wire contacting ground.
- With the circuit isolated as directed by the manufacturer, check the sensor signal for a short to ground and inspect the sensor's ground and reference connections.
- Test internal temperature sensor A and its wiring against the manufacturer's procedure to distinguish a shorted sensor from a harness fault.
- If the sensor circuit passes, check the compressor control module connector and input circuit using the manufacturer's diagnostic procedure.
Common fixes
- Clean and secure corroded or loose sensor A connector pins.
- Repair the signal wire where it is shorted to ground.
- Replace internal temperature sensor A if it fails the manufacturer's test.
- Repair or replace the compressor control module if its input circuit is confirmed faulty.
Can I keep driving?
Driving is generally possible with the A/C off, but cooling may be limited or disabled. Do not rely on A/C until the fault is repaired, and take extra care if cabin cooling is needed to keep occupants safe.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.