P07C3

What it means

P07C3 is a generic powertrain code meaning the transmission control unit has detected a low signal on the circuit of input/turbine shaft speed sensor 'C'. The voltage or signal from that sensor sat below the expected range, typically from a short to earth, an open circuit or a failed sensor. Which sensor is 'C', and where it sits, depends on the transmission design, so check the manufacturer's information for the specific model.

Symptoms

• Gearbox warning light or engine management light on
• Transmission in limp-home mode, often stuck in one gear
• Harsh, delayed or flared gear changes
• Erratic or inoperative speedometer or rev-related gauges on some models
• Torque converter lock-up not engaging, with poorer fuel economy
• Gearbox refusing to shift manually or up or down normally

Possible causes

• Damaged, chafed or shorted wiring between the speed sensor and the transmission control unitlikely
• Faulty input/turbine shaft speed sensor Clikely
• Corroded, loose or contaminated connector pins at the sensor or transmission pluglikely
• Transmission fluid contamination with metal particles affecting a magnetic sensor, or fluid ingress into the connectorpossible
• Damaged or incorrectly fitted sensor reluctor or tone ring, or incorrect sensor air gap (design dependent)possible
• Fault in the transmission control unit or its power and earth suppliesrare
• Outdated control unit software where the manufacturer has issued a fix for this coderare

How to diagnose

1. Read all stored and pending codes and note the freeze frame data, including gear, vehicle speed and engine speed when the code set
2. Check for other speed sensor, solenoid or communication codes that point to a shared wiring or power fault
3. Check transmission fluid level and condition, looking for burnt smell, debris or fluid in the connector
4. Inspect the sensor wiring and connectors for chafing, heat damage, corrosion, and fluid wicking along the harness
5. Using the manufacturer's data, identify which sensor is 'C' and check its resistance or signal, as applicable to the sensor type
6. With the connector unplugged, test the wiring for short to earth, open circuit and short to supply, and check the control unit supply and earth
7. Watch live input shaft speed against engine and output speed on a road test to see if the signal drops out or reads zero
8. Check for relevant technical service bulletins or software updates for the model and gearbox

How to fix

• Repair or replace damaged wiring and fix any chafed sections, using proper sealed repairs
• Clean, repair or replace corroded or damaged connectors and terminals
• Replace the faulty speed sensor and ensure it is correctly seated and sealed
• Rectify fluid contamination: correct the fluid level or condition and repair any source of metal debris, which may need gearbox inspection
• Replace damaged tone ring or reluctor components, as the transmission design requires
• Update the control unit software only if the manufacturer lists it as a fix, or repair or replace the unit after confirming supply and earth are sound

Can I keep driving?

Nearby codes

• P07C2GenericInput/Turbine Shaft Speed Sensor B Circuit High
• P07C4GenericInput/Turbine Shaft Speed Sensor C Circuit High