Error Code P0903 is defined as Clutch Actuator Circuit High. This is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to the present. This code appears in vehicles with transmission fluid temperature sensors. This includes vehicles from, but not limited to, Ford, Hyundai, Mercedes Benz, Smart, and Toyota. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

The clutch actuator circuit works by engaging and disengaging the clutch or clutches on semi-automatic transmission. Depending on the specifications and configurations of the vehicle, it comes equipped with multiple sensors and associated with a variety of components to accomplish its task. Some configurations include two hydraulic clutches, one for even gears and another one for odd gears. For newer vehicles, the number of gears ranges from 6 to 9. This design enables gear smooth and seamless gear changes, similar to a fully automatic transmission.

When the Powertrain Control Module (PCM), Electronic Control Module (ECM), or Transmission Control Module (TCM) determines a high voltage or resistance condition in the clutch actuator circuit, the Error Code P0903 will be set. Subsequently, the check engine light or transmission warning lamp will be activated.

Other related error codes include:

  • Error Code P0900
  • Error Code P0901
  • Error Code P0902

Common Symptoms

  • Motor not cranking (a safety precaution activated by the PCM)
  • Engine stalls while driving or after a control system failure
  • Transmission in Limp Mode
  • Transmission stuck in one gear (but doesn’t enter limp mode)
  • Check engine light and transmission warning light activated

Possible Causes

  • Faulty clutch actuator
  • Faulty sensor or solenoid
  • Damaged or faulty wiring
  • Defective or loose control module ground strap
  • Corroded, damaged, or loose connector
  • Faulty fuse or fuse-able link (If applicable)
  • Malfunctioning clutch master cylinder
  • Faulty ECM, PCM, or TCM

How to Check

Check with the Technical Service Bulletin. Look for the specific vehicle by year, model, and power plant.

Find and look for obvious damage in the components associated with the clutch actuator circuit. Inspect thoroughly, including the wires. Look for signs of rubbing, scraping, burn spots, and bare wires.

Check the connection security of the connectors. Look for signs of corrosion or damage on the pins. Ensure you check all related wiring connectors and connections to actuators, control modules, solenoids, and all sensors. Refer to the specific tech data for the vehicle to see if a fuse-able link is incorporated into the circuit.

Advanced Steps

This could be vehicle-specific and require advanced equipment to perform correctly.

You will need a digital multi-meter and the vehicle’s specific technical references. This includes troubleshooting charts and the appropriate sequence to follow, assisting you with an accurate diagnosis. Voltage Checks

Voltage Checks

A voltage check must be done using the specific troubleshooting guidelines for the vehicle to identify the proper sequence and acceptable ranges for the proper operation. This can vary from one vehicle make and model to another.

Suppose voltage check is able to identify the absence of the power source or ground. In that case, you need to conduct continuity testing to inspect the integrity of the connectors, wirings, and other components. Ensure you remove the power from the circuit, and the normal readings for the connections and wirings are at 0 ohms or resistance. Resistance (no continuity) means there is a fault in the wiring (open or shorted) and must be repaired or replaced.

Continuity tests from the PCM, ECM, and TCM will confirm ground straps and ground wires’ serviceability. Resistance means there is a loose connection or corrosion.

How to Fix

  • Replacement of the clutch actuator
  • Replacement of faulty sensor or solenoid
  • Replacement of clutch master cylinder
  • Cleaning of corrosion from the connectors
  • Repair or replacement of faulty wiring
  • Replacement of blown fuse or fuse-able link (if necessary)
  • Repair or replacement of defective ground straps
  • Flashing and replacement of PCM, ECM, or TCM

This code’s severity worsens if the vehicle is unable to shift properly, causing damage to the internal components of the transmission.

When repairing this code, the most common mistake is replacing the actuator, clutch master cylinder, sensor, solenoid, or the control module when faulty wiring is the problem.