01 Mastering Fuel System Troubleshooting: Tips, Solutions, and… • 02 The Heart of Automatic Transmissions: A Closer Look at Torq… • 03 This Engine Feature Saves Gas But Could Bankrupt Your Wallet • 04 Diagnosing and Fixing Noisy Car Problems • 05 Smooth Shifting: Navigating Common Transmission Problems an… • 06 The Best Cars That Porsche Has Ever Made • 07 The Challenges of CVT Gearboxes: Troubleshooting and Repair • 08 Decoding the Engine Control Unit (ECU): Inputs, Outputs, an… • 09 Understanding and Using the Shift Lock Mechanism in Automat… • 10 How a Car Engine Actually Works From Start to Finish •

DTC codes / P2Cxx · Hybrid propulsion / P2C42

P2C42Fan 4 Performance/Stuck Off

P2C42 indicates that the powertrain control module (PCM) has commanded the fourth cooling fan circuit on, but the fan feedback signal does not match the expected state, so the PCM flags a performance or stuck-off condition. The computer typically detects this by comparing the fan's actual current draw or feedback voltage against the commanded state and finding no response when the fan should be running.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the check engine light (malfunction indicator lamp) on the dashboard.
  • Often no symptoms besides the warning light, especially if the fan is not needed for current driving conditions.
  • Engine coolant temperature may rise above normal in traffic or during extended idle.
  • The fourth fan may not run at all when the PCM commands it on, leading to reduced cooling capacity.
  • Possible activation of a fail-safe mode that limits engine power or disables certain functions to protect the engine.
  • In some vehicles, a message on the driver information center indicating reduced engine power or service required.

Common causes, most likely first

  1. Failed cooling fan motor or seized fan bearing, preventing rotation even when powered.
  2. Open or shorted wiring in the fan control circuit, including damaged connectors or corroded terminals.
  3. Blown fuse or faulty relay dedicated to the fourth fan circuit.
  4. Faulty fan control module or solid-state relay that does not supply power to the fan.
  5. PCM software issue or internal driver failure for the fan output.
  6. Poor ground connection for the fan motor or control module.
  7. Aftermarket or incorrect fan assembly that does not meet the vehicle's electrical specifications.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in other modules before proceeding.
  2. Inspect the fan fuse and relay for the fourth fan circuit, replacing any blown fuse or faulty relay.
  3. Visually inspect the fan connector and wiring for damage, corrosion, or loose pins, and repair as needed.
  4. Command the fan on using a scan tool bidirectional control and observe whether the fan runs and whether the feedback signal changes.
  5. Measure voltage and resistance at the fan motor connector while commanding the fan on to confirm power and ground delivery.
  6. If the fan does not run with direct power applied, replace the fan motor or assembly.
  7. If the fan runs with direct power but not under PCM command, test the control circuit back to the PCM and repair any open or short, or replace the PCM if the driver is faulty.

Fan circuit checks that techs often skip

  • A fan that spins freely by hand can still fail electrically, so always confirm current draw or feedback voltage rather than relying on visual inspection alone.
  • The fourth fan circuit is often part of a multi-fan array, and a failure in one fan can cause the PCM to set codes for multiple fans if they share a common power or ground point.
  • Some vehicles use a pulse-width modulated (PWM) signal to control fan speed, and a stuck-off code can be set by a fan that runs only at full speed or not at all due to a faulty PWM module.
  • A weak battery or charging system can cause intermittent fan operation and set this code without any hard fault in the fan circuit itself.
  • After replacing a fan, the PCM may need to relearn the fan feedback values; failing to perform a relearn can cause the code to return immediately.

Can I keep driving with P2C42?

It is generally safe to drive short distances with this code if the engine temperature remains normal, but avoid heavy loads, extended idling, or hot weather until repaired. If the temperature gauge climbs above normal or a warning message appears, stop and let the engine cool to prevent damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage