What it means
The ECM detects a circuit intermittent/erratic fault on the a/c compressor control module internal temperature sensor b 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
The A/C compressor control module uses its internal temperature sensor B reading to manage compressor operation and protect the unit from unsuitable temperatures. The ECM monitors that sensor's circuit for a stable signal; this code sets when the reading becomes intermittent or erratic enough that it cannot be relied on for control.
Common causes
Most likely first.
- Sensor connector not seated
- Noisy ground reference
- Connector with intermittent contact under vibration
Symptoms
- Check-engine light may be on
- Air conditioning may work intermittently or be reduced
How to diagnose it
- Use a scan tool to record freeze-frame data and watch the compressor module's temperature sensor B reading while the fault is present.
- Check whether A/C operation changes at the same time as the sensor B reading drops out or jumps.
- Inspect the sensor B connector for a loose fit, damaged pins, corrosion, or signs that vibration could interrupt contact.
- Follow the sensor B wiring and check for chafing, pinching, or loose ground connections that could make the signal unstable.
- With the correct wiring information, test sensor B circuit continuity and ground stability while gently moving the harness, then compare results with the manufacturer's specification.
Common fixes
- Reseat and secure the compressor control module's sensor B connector.
- Clean or repair corroded or loose connector terminals.
- Repair damaged sensor B wiring or its ground connection.
- Replace the internal temperature sensor or compressor control module if circuit tests confirm an internal fault.
Can I keep driving?
If the vehicle drives normally, limited driving is generally possible, but A/C may cut out or be reduced. Avoid relying on the air conditioning until the intermittent temperature reading is repaired.
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.