Clutch Pedal Switch "B" Circuit Low
The PCM has detected a fault in the clutch position sensor circuit. The clutch position sensor circuit is sometimes called the clutch start switch because it must be closed for the starter to engage. This code applies only to vehicles equipped with a manual transmission. If this code is exhibited in a vehicle with an automatic transmission, suspect a defective PCM or programming error.
Code Set Parameters
If the PCM detects an abnormal voltage or resistance reading from the clutch position sensor circuit, a code will be stored and a malfunction indicator lamp may be illuminated. Some vehicles will require multiple failure cycle in order for a service engine soon lamp to be illuminated and some models will not illuminate a service engine soon lamp at all.
Symptoms may range from non-existent or could include failure of the engine to start, the engine may start without the clutch depressed, a stored code, and an illuminated service engine soon lamp.
The most common causes of this type of malfunction code being stored are due to a defective or misadjusted clutch position sensor. Other possible causes include shorted, open, or corroded wiring and/or electrical connectors.
Technicians report that the starter/solenoid is frequently condemned in error when the clutch position sensor is at fault.
- A scanner (or code reader) and a digital volt/ohmmeter will be helpful in successfully diagnosing the potential causes of this code.
In most modern OBD-II applications the clutch position sensor (also called the clutch start switch) is used to close the circuit between the ignition switch and the starter solenoid assembly
While the clutch position sensor (or clutch interrupter) switch may vary by design from one manufacturer to another, it is usually of the “on/off” contact variety and is stationary mounted near the clutch foot pedal on the support bracket
- Some models place the switch directly on the pedal lever and use the pivot point as a fulcrum to move the contacts and open/close the circuit
- Regardless of design, constant voltage is typically present on one side of the switch and when the contacts in the switch are closed, voltage is transferred across the contacts and out of the switch to the starter or starter relay
Begin your diagnosis with a visual inspection of all wiring and connectors
- Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
- Always retest the system after repairs are completed to ensure success.
If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
- This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
- After the codes are cleared, operate the vehicle to see if the code returns
- If the code fails to immediately return, you may have an intermittent condition
- Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made
If the code immediately returns, check for battery voltage on the input side of the clutch position sensor using the digital volt/ohmmeter
- If there is no voltage present on the input side of the switch, disconnect any related control modules and check for continuity between the system fuse and the input circuit at the clutch position sensor
- Repair open or shorted circuits as required
If voltage is present on the input side of the clutch position sensor, depress the clutch pedal and check for voltage on the output side of the clutch position sensor
- If you have voltage on the input side and none on the output side (when the clutch pedal is depressed) suspect a faulty or misadjusted clutch position sensor
- Adjust or replace the switch as needed and retest the system afterward to ensure a successful repair.
If there is voltage present on the output circuit of the clutch position sensor, check circuit continuity and resistance between the switch and the PCM
- Take care to disconnect all related control modules before testing
- Again, refer to the vehicle wiring diagram to ensure that all circuits are tested
- Repair or replace system open or shorted circuits/connectors as required
If all circuits coincide with manufacturer’s specifications, suspect a defective PCM
- Remember that PCM failure is rare and replacement will require reprogramming