P07C4
Input/Turbine Shaft Speed Sensor C Circuit High.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 7
- AreaTransmission
- C4
- FaultThe specific fault in that area
What it means
P07C4 is a generic powertrain code meaning the transmission control unit has detected a high voltage or signal on the circuit of input/turbine shaft speed sensor 'C'. The control unit saw a signal level above the expected range, which usually points to an open circuit, a short to voltage or a faulty sensor. Which sensor is 'C' and where it sits depends on the transmission, so check the manufacturer's information for the specific model.
Symptoms
- Warning light on (engine management or transmission warning)
- Transmission may enter limp mode or fixed gear
- Harsh, delayed or flared gear changes
- Speedometer or rev reading erratic, if the signal is shared
- Reduced performance or poor economy
- Torque converter lock-up not operating
Possible causes
- Faulty input/turbine shaft speed sensor Clikely
- Damaged, chafed or open-circuit wiring to the sensorlikely
- Short to voltage in the signal or supply circuitpossible
- Corroded, loose or contaminated connector terminalspossible
- Metallic debris or damaged reluctor/target ring affecting the signalpossible
- Faulty transmission control unit or internal transmission harness (mechatronic unit on some designs)rare
How to diagnose
- Read all stored and pending codes and note freeze frame data, including vehicle speed, gear and transmission temperature
- Check for related speed sensor or gear ratio codes and any technical service bulletins for the model
- Inspect the sensor, wiring and connector for damage, oil ingress, corrosion, bent pins or chafing
- Check transmission fluid level and condition, looking for metal debris or contamination (procedure varies by transmission)
- With live data, compare input shaft speed with engine speed and output speed to see if the reading is implausible or stuck high
- Test the sensor supply, signal and earth circuits against the manufacturer's wiring diagram, checking for shorts to voltage or open circuits
- Test the sensor resistance or output against the specification for that transmission
- Clear the code and road test to confirm whether it returns
How to fix
- Replace the faulty speed sensor C
- Repair or replace damaged wiring, and fix any short to voltage or open circuit
- Clean or repair connector terminals, or replace the connector
- Correct fluid level or service the transmission, and repair any internal fault causing debris or a damaged target ring
- Repair or replace the internal harness or transmission control unit only once all else is ruled out and as per manufacturer procedure
Can I keep driving?
The car can usually be driven carefully a short distance, but limp mode and harsh shifts may occur, which can stress the transmission. Get it diagnosed soon and avoid heavy loads or towing meanwhile.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.