P2C3E

Code

Generic P — Powertrain

Fan 4 Control Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 25 EN: 38 RU: 23

AI status

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Page language: EN

Causes

Open or short in wiring harness to Fan 4
Corroded or disconnected connector at fan, relay, or ECM
Failed fan motor (stalled or high resistance)
Bad fan relay or blown fuse
Faulty ECM/driver output for Fan 4
Intermittent/loose ground or power supply

Symptoms

Cooling fan 4 does not operate when commanded
Cooling fan 4 runs continuously regardless of command
Engine temperature higher than normal or overheating
Reduced A/C cooling performance at low speeds
Malfunction Indicator Lamp (MIL) or related warning illuminated
Intermittent fan operation or unusual fan noise

What to check

Read and record freeze-frame data and related codes with scan tool
Visual inspection of wiring, connectors, pins, and fan assembly for damage or corrosion
Check relevant fuses and relays for Fan 4 and replace if faulty
Backprobe fan connector while commanding fan ON and OFF; measure voltage and ground presence
Measure continuity and resistance between ECM control pin and fan connector
Bench-test fan motor directly with battery (observe current draw and operation)

Signal parameters

Control type: switched ground, switched battery, or PWM output (vehicle dependent)
Voltage range: 0 V (off) to approximately battery voltage (on) ~11–14 V
PWM duty cycle: 0–100% depending on commanded torque/temperature
Typical PWM frequency (if used): commonly ~20–300 Hz (manufacturer dependent)
Typical fan motor current draw: varies by vehicle; commonly single-digit to tens of amps (measure to verify)

Diagnostic algorithm

Retrieve stored data: record freeze-frame, related codes, and live data for fan status and commanded outputs.
Visual inspection: check harness, connectors, pins, fan assembly, relay and fuse for obvious damage or corrosion.
Verify power and ground: with the ignition ON, check for battery voltage at the fan power feed and a good ground at the fan motor.
Command fan ON via scan tool while backprobing the control pin: measure control voltage or PWM; note duty cycle and frequency (if present).
Direct bench test: disconnect fan connector and apply battery power directly to fan to confirm motor operation and measure current draw. Do this only when safe and with fan secured.
Continuity and resistance: with battery disconnected, measure resistance between ECM control pin and fan connector; check for shorts to battery or ground.
Relay/fuse check: swap or bench-test relay and inspect fuse circuit for intermittent faults.
If wiring and fan motor test good, consider ECM driver failure: verify with manufacturer service information; replace or reprogram ECM only after confirming external circuit integrity.
After repairs, clear codes and perform functional test under various conditions (A/C on/off, different engine temps). Retest for reappearance of the code.

Likely causes

Damaged wiring or pin corrosion at fan connector
Blown fuse or failed relay controlling fan circuit
Fan motor failure under load
Failed ECM driver transistor for fan output

Fault status

⚠️ Status

Manufacturer-specific code indicating a fault in the Fan 4 control circuit — possible open, short, high resistance, connector/relay/fuse issue, motor failure, or ECM driver fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours