Technical Description of OBD-II Trouble Code
Performance Issue in Bank 2 Charge Air Cooler Temperature Sensor Circuit
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles with a charge air cooler temperature sensor (Chevy, Ford, Toyota, Mitsubishi, Audi, VW, etc.). While it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
A turbocharger functions as an air pump that forcefully supplies air to the engine. It consists of two sections: the turbine and the compressor.
The turbine is connected to the exhaust manifold and is driven by exhaust gases. The compressor is attached to the air intake. Both sections are linked by a shaft, so when the turbine spins, the compressor also spins, allowing intake air to enter the engine. Cooler air results in a denser intake charge, leading to increased power. For this reason, many engines are equipped with a charge air cooler, also known as an intercooler. Charge air coolers can be either air-to-liquid or air-to-air coolers, but their purpose remains the same – to cool the air entering the intake.
A charge air cooler temperature sensor (CACT) is used to measure the temperature and density of the air entering or exiting the charge air cooler. This information is sent to the powertrain control module (PCM), where it is compared to the intake air temperature (and sometimes the engine coolant temperature and exhaust gas recirculation temperature) to assess the performance of the charge air cooler. The PCM sends a reference voltage (typically 5 volts) through an internal resistor and measures the voltage to determine the charge air cooler temperature.
Note: In some cases, the CACT is integrated into the boost pressure sensor.
Code P00A1 is triggered when the PCM detects a malfunction in the bank 2 charge air cooler temperature sensor. Bank 2 refers to the second bank of the engine, which does not include cylinder #1.
Related diagnostic codes for the circuit of the bank 2 charge air cooler temperature sensor include:
P00A0 Charge Air Cooler Temperature Sensor Circuit Bank 2
P00A2 Charge Air Cooler Temperature Sensor Circuit Low Bank 2
P00A3 Charge Air Cooler Temperature Sensor Circuit High Bank 2
P00A4 Charge Air Cooler Temperature Sensor Circuit Intermittent/Erratic Bank 2
Code Severity & Symptoms
These codes have a moderate severity level.
Symptoms of an engine code P00A1 may include:
Illuminated check engine light
Poor engine performance
Decreased fuel economy
Vehicle stuck in “limp” mode
Diesel particulate filter regeneration inhibited (if equipped)
Causes
Possible causes for the P00A1 code include:
Faulty sensor
Wiring issues
Failed or restricted charge air cooler
Faulty PCM
Diagnostic and Repair Procedures
Begin by visually inspecting the charge air cooler temperature sensor and its corresponding wiring. Look for loose connections, damaged wiring, etc. Also, visually inspect the charge air cooler and ducting. If any damage is found, repair it as necessary, clear the code, and check if it reappears.
Next, check for any technical service bulletins (TSBs) related to this issue. If no relevant TSBs are found, proceed with step-by-step diagnosis of the system.
The following is a general procedure, as the testing process for this code varies between vehicles. To accurately test the system, refer to the manufacturer’s diagnostic flow chart.
Perform some preliminary circuit testing: Use a scan tool to monitor the charge air coolant temperature sensor data parameter. Disconnect the CACT sensor; the scan tool value should drop to a very low value. Next, connect a jumper wire across the terminals. If the scan tool now displays a very high temperature, the connections are intact and the ECM can recognize the input. This indicates that the problem most likely lies with the sensor rather than a circuit or PCM issue.
Test the sensor: Disconnect the charge air cooler temperature sensor connector. Then, measure the resistance between the two sensor terminals using a digital multimeter set to ohms. Start the engine and observe the meter value; the values should decrease smoothly as the engine warms up (check the engine temperature gauge on the dashboard to ensure the engine reaches operating temperature). If the engine temperature increases but the CACT resistance does not decrease, the sensor is faulty and should be replaced.
Check the circuit
Check the reference voltage side of the circuit: With the ignition on, use a digital multimeter set to volts to check for a 5-volt reference from the PCM at one of the two charge air cooler temperature sensor terminals. If no reference signal is present, connect the meter set to ohms (with the ignition off) between the reference voltage pin on the CACT and the reference voltage pin on the PCM. If the meter reads “out of limits” (OL), there is an open circuit between the PCM and sensor that needs to be located and repaired. If the meter reads a numeric value, there is continuity.
If everything is functioning properly up to this point, check that there is a 5-volt reference coming out of the PCM at the reference voltage terminal. If there is no 5-volt reference from the PCM, the PCM is likely faulty.
Check the ground side of the circuit: Connect the meter set to ohms (with the ignition off) between the ground terminal on the charge air cooler temperature sensor and the ground terminal on the PCM. If the meter reads “out of limits” (OL), there is an open circuit between the PCM and sensor that needs to be located and repaired. If the meter reads a numeric value, there is continuity. Finally, check that the PCM has a good ground by attaching one meter lead to the PCM ground terminal and the other to chassis ground. Once again, if the meter reads “out of limits” (OL), there is an open circuit between the PCM and ground that needs to be located and repaired.
