P007C - Charge Air Cooler Temperature Sensor Circuit Low (Bank 1)
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P007C is a generic OBD-II code indicating that the Engine Control Unit (ECU) has detected an unexpectedly low voltage from the Charge Air Cooler (CAC) temperature sensor on Bank 1. This sensor monitors the efficiency of the intercooler by measuring air temperature after the turbocharger. The sensor typically operates as a NTC thermistor. A 'Circuit Low' condition usually signifies a short circuit to ground in the signal wire or an internal sensor failure that pulls the signal voltage below the calibrated threshold (typically <0.2V). Accurate temperature data is essential for the ECU to manage air density calculations, boost pressure, and ignition timing.
Possible Causes
Faulty Charge Air Cooler (CAC) temperature sensor (internal short)
Wiring harness damaged or shorted to ground in the signal circuit
Corrosion or short circuit within the sensor connector
Failed Engine Control Unit (ECU)
Symptoms
Recommended Solution
- Visual Inspection: Check the CAC sensor wiring and connector for fraying, oil contamination, or heat damage.
- Reference Voltage Test: Disconnect the sensor and turn on ignition. Measure between the reference wire and ground; you should see a steady 5.0V from the ECU.
- Ground Circuit Test: Ensure the sensor ground wire has good continuity to chassis ground (< 0.5 Ohms).
- Sensor Bench Test: Measure resistance (Ohms) across the sensor pins. Compare with manufacturer specs (e.g., 2000-3000 Ohms at 20°C). If resistance is near 0 Ohms, the sensor is internally shorted.
- Advanced Diagnosis: Monitor live data using a scan tool. If the temperature reading is stuck at maximum (e.g. 150°C+) even with a cold engine, it confirms a short to ground.
- Component Replacement: Replace the faulty sensor and clear the DTCs.
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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