P2BDC

Code

Generic P — Powertrain

Motor Electronics Coolant Temperature Sensor C Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 29 EN: 27 RU: 24

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Page language: EN

Causes

Open or short in coolant temperature sensor C wiring
Poor connector contact (corrosion, bent pins, water intrusion)
Failed coolant temperature sensor (NTC sensor)
Faulty ECM power, reference or ground for the sensor circuit
Intermittent wiring damage (chafing, heat, movement)
Incorrect sensor installed or wrong resistance characteristic

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Incorrect temperature gauge reading or no movement
Poor cold/hot idle behavior or hard starting when hot/cold
Reduced engine performance or torque management
Radiator fan operation may be incorrect or inoperative

What to check

Read freeze frame and live data for the coolant temperature sensor C
Scan for additional related codes (other ECT circuits, power/ground faults)
Visually inspect sensor, connector, and wiring for damage, corrosion, or contamination
Backprobe sensor connector and verify reference voltage and signal with key on, engine off
Measure sensor resistance at known temperatures (compare to spec) or measure output voltage while warming engine
Check ECM power and ground integrity for that circuit

Signal parameters

Typical reference voltage from ECM: ~5.0 V (some systems use 3.3 V) — should be present at sensor connector
Expected sensor signal (voltage) behavior: HIGH voltage when cold (~4.0–4.9 V) and LOW when hot (~0.2–1.0 V), depending on design
Typical NTC resistor range (approximate): cold (~0–20°C) several kilo-ohms; hot (~80–100°C) a few hundred ohms — consult vehicle spec
Open-circuit: signal floats toward reference voltage or no continuity; short-to-ground: signal near 0 V; short-to-battery: signal near reference voltage with no change

Diagnostic algorithm

Retrieve trouble code, freeze frame, and live data. Note conditions when code set (temp, run time, voltage).
Inspect the sensor C connector and wiring for physical damage, corrosion, melted insulation, or evidence of water ingress.
With ignition ON (engine OFF), backprobe the connector: verify ECM reference voltage present and a good ground. If no reference, suspect ECM or fused supply.
Measure the sensor signal voltage while warming the engine: voltage should decrease smoothly as temperature rises. If it is stuck high/low or erratic, proceed.
Remove sensor and measure resistance at ambient and warmed temperatures; compare to manufacturer specification. If resistance out of range, replace sensor.
Check continuity between sensor signal and ECM pin; check for short to ground or battery using an ohmmeter with circuit de-energized.
If wiring and sensor test good, inspect ECM connector and pins. Wiggle test wiring while monitoring live data to expose intermittent faults.
If all wiring and sensor check okay, suspect ECM input failure. Confirm with manufacturer diagnostics before ECM replacement.
Repair or replace defective wiring, connector, or sensor as required, clear codes, and perform a road test to verify the repair.

Likely causes

Damaged sensor harness between sensor and PCM
Corroded or loose sensor connector
Short to battery or ground on the sensor signal or reference
Failed coolant temperature sensor
PCM input circuit fault (less common)

Fault status

⚠️ Status

ECM detected abnormal or out-of-range signal on Coolant Temperature Sensor C circuit — possible open, short to ground/battery, intermittent connection, or faulty sensor.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours