Code P007C: Low Circuit Value for Charge Air Cooler Temperature Sensor
Understanding Fault Code P007C
The generic code P007C belongs to the powertrain group and indicates a circuit problem with the Charge Air Cooler Temperature (CACT) sensor, typically a short circuit on bank 1. This code applies to most vehicles equipped with a turbocharger and an OBD-II system (Chevrolet, Ford, Toyota, Audi, VW, etc.). Precise diagnostic procedures may vary by manufacturer and model.
Role of the Sensor and Turbocharger
The turbocharger forces air into the engine to increase its power. It consists of two sections: a turbine, driven by exhaust gases, and a compressor, which draws in intake air. A charge air cooler (intercooler), either air-to-air or air-to-liquid, is often used to cool this compressed air, thereby increasing its density and combustion efficiency.
The Charge Air Cooler Temperature (CACT) sensor measures the air temperature at the intercooler outlet. The PCM (Powertrain Control Module) uses this data, often comparing it with other temperatures (intake air, coolant), to optimize engine operation. It sends a 5V reference voltage to the sensor and measures the return voltage to determine the temperature.
Note: The CACT is sometimes integrated with the Manifold Absolute Pressure (MAP) sensor.
Symptoms and Severity of Fault P007C
The severity of this code is moderate. A vehicle with this fault may exhibit the following symptoms:
- Malfunction Indicator Lamp (Check Engine) illuminated
- Reduced engine performance and power loss
- Decreased fuel economy
- Activation of limp mode
- Inhibition of Diesel Particulate Filter (DPF) regeneration on diesel engines
Possible Causes of Code P007C
Several components can be the source of this code:
- Faulty temperature sensor (CACT)
- Wiring issue (short circuit, open circuit, loose or corroded connector)
- Obstructed or damaged charge air cooler
- Rare PCM failure
Diagnostic and Repair Procedures
1. Visual Inspection: Start by inspecting the sensor, its connector, and associated wiring. Look for signs of damage, corrosion, or loose connections. Also inspect the charge air cooler and its ducts for any restrictions or leaks. Repair or replace damaged components, clear the codes, and perform a road test.
2. Consultation of Technical Service Bulletins (TSBs): Check with the manufacturer for any TSBs related to this specific issue for your vehicle model.
3. Sensor and Circuit Testing: The following steps are general. Always consult specific manufacturer data for the exact procedure.
- Preliminary Test: Using a diagnostic tool, observe the CACT temperature value. Disconnect the sensor connector. The displayed value should drop sharply. Then, short the two pins of the connector with a jumper wire. The value should now display a very high temperature. If this occurs, the circuit and PCM appear functional, pointing to a faulty sensor.
- Sensor Test: Disconnect the sensor and measure its resistance (Ohms) using a multimeter. On a cold engine start, the resistance should gradually decrease as the engine (and thus the air) warms up. If the resistance does not change or is inconsistent, the sensor is likely faulty.
- Reference Circuit (5V) Test: Engine OFF, ignition ON. Using a multimeter (Volts), check for the presence of 5V on the reference voltage pin of the sensor connector. If absent, check the continuity (Ohms, ignition OFF) between this pin and the corresponding pin at the PCM to identify a possible break.
- Ground Test: Ignition OFF. Check the continuity (Ohms) between the ground pin of the sensor connector and the corresponding ground pin at the PCM. Also verify that the PCM itself has a good ground connection to the chassis.
Conclusion: If the sensor and wiring are in good condition and the 5V signal from the PCM is absent, the PCM itself might be faulty (rare case).
Need Additional Help?
Electrical diagnosis can be complex. If you are not equipped or familiar with these procedures, consult a professional mechanic for an accurate diagnosis and reliable repair. Use a quality OBD2 diagnostic tool to read and clear fault codes.