Code P00A4: Intermittent Charge Air Cooler Temperature Sensor Circuit, Bank 2
The engine trouble code P00A4 is a generic powertrain code indicating an intermittent issue in the Charge Air Cooler Temperature (CACT) sensor circuit on engine bank 2. This problem affects engine performance and requires diagnosis.
Role of the Sensor and the Charge Air Cooler
The turbocharger forces air into the engine to increase its power. The compressed air heats up and must be cooled by the charge air cooler (or intercooler) to increase its density. The temperature sensor (CACT) measures the temperature of this cooled air and sends the signal to the Powertrain Control Module (PCM). The PCM uses this data, often comparing it to other temperatures (intake, coolant), to optimize engine operation.
Symptoms of Code P00A4
- Check Engine Light illuminated
- Poor performance and power loss
- Reduced fuel economy
- Limp mode activated (“limp home mode”)
- Diesel particulate filter regeneration inhibited (if applicable)
Possible Causes of the Fault
- Faulty or failing CACT sensor
- Wiring issues: loose connections, damaged wires, corrosion
- Clogged or faulty charge air cooler
- Rare PCM failure
Diagnostic Procedure
⚠️ Caution: This procedure is general. Always consult manufacturer-specific information for your vehicle.
- Visual Inspection: Inspect the sensor, its connector, and the wiring. Look for any signs of damage, corrosion, or loose connections. Also check the condition of the cooler and its air ducts.
- Sensor Test:
- With the engine cold, disconnect the sensor connector.
- Measure its resistance (Ohms) between its two terminals using a multimeter.
- Start the engine. The resistance should gradually decrease as the engine warms up. If the value remains stable or erratic, the sensor is most likely faulty.
- Circuit Test:
- Reference Voltage (5V): Ignition on, check for the presence of 5V at the corresponding terminal of the sensor connector. If absent, check the wire continuity back to the PCM.
- Ground: Ignition off, check the continuity between the ground terminal of the connector and the PCM ground, and between the PCM and the chassis ground.
- Diagnostic Tool Test: Use an OBD2 scanner to monitor the sensor’s live data (CACT parameter). Disconnect the sensor: the displayed value should drop. Short the connector pins: the value should spike. This confirms that the PCM and circuit are functioning, pointing to a faulty sensor.
Repair and Advice
After identifying and correcting the cause (replacing the sensor, repairing wiring, cleaning the cooler), clear the trouble codes with your diagnostic tool. Perform a road test to verify that the P00A4 code does not reappear.
Need help? Electrical diagnosis can be complex. If you are not comfortable with these procedures, consult a professional mechanic for an accurate diagnosis and reliable repair.