|Trouble Code||Fault Location||Probable Cause|
|P0901||Clutch actuator -circuit range/performance||Wiring, poor connection, clutch actuator, ECM/PCM/TCM|
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What Does Code P0901 Mean?
OBD II fault code P0901 is a generic code that is defined as “Clutch actuator -circuit range/performance”, and is set when the PCM (Powertrain Control Module) detects a problem in the control circuit of the clutch actuator that affects the range or performance of the clutch actuator. Note that code P0902 refers to a problem with either the clutch actuator itself, or with the clutch actuator’s control circuit.
On applications that are fitted with automated manual transmissions, which are normal manual transmissions that are fitted with computer-controlled shift mechanisms, the clutch is also controlled by the PCM by means of an actuator that can be electrically (most commonly) or hydraulically operated.
When the PCM determines that a shift point had been reached, it actuates the clutch to decouple the transmission from the engine, after which actuators deselect the current gear, and depending on the operating conditions, selects the next higher or lower gear. When the PCM receives confirmation from various position sensors that the next gear had been selected successfully, it again activates the clutch actuator to re-engage the clutch, which “reconnects” the engine to the transmission. Note that the position of the clutch actuator is continually being monitored by the PCM.
Thus, when the PCM detects a fault condition, electrical failure, or malfunction in the actuator control circuit that prevents the clutch actuator from fully disengaging/re-engaging the clutch, or if it receives a signal from the clutch actuator position sensor that does not agree with the desired or expected position of the clutch actuator it will set code P0901, and may also illuminate a warning light.
The image below shows a typical clutch actuator but note that the appearance, and operating principles of clutch actuators vary between manufacturers. Refer to the manual for the application for details on the location and operating principles of the clutch actuator on the affected application.
What are the common causes of code P0901 ?
Some common causes of code P0901 could include the following-
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors
- Defective clutch actuator
- Low fluid level if the actuator is hydraulically operated
- Defective position switch/sensor
- Worn clutch components
- Mechanical failure of clutch components
- Failed or failing PCM/TCM. Note that control module failure is a rare event, and the fault must be sought elsewhere before any control module is replaced
What are the symptoms of code P0901 ?
Some common symptoms of code P0901 could include the following-
- Stored trouble code and possibly an illuminated warning light
- Additional transmission related codes may be present
- Varying degrees of clutch slippage may be present
- Gear shifts may be harsh or unpredictable
- In some cases, the transmission may be held in a fail-safe or limp mode until the problem is resolved
- Engine may stall when coming to a stop
How do you troubleshoot code P0901 ?
NOTE: Some Jeep, Chrysler and Fiat models that were built between 2014 and 2016 for the NAFTA, LATAM, EMEA and APAC markets, and that have undergone the S55 safety recall, may experience code P0901 that may be accompanied by serious driveability concerns and issues. On these models, the problem can be resolved by replacing the entire transmission harness with an upgraded OEM harness.
Record all fault codes present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.
Refer to the manual to locate the clutch actuator and its associated wiring. Determine the function and color coding of all wiring to avoid a misdiagnosis.
Perform a thorough visual inspection of all wiring and look for damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors. Replace wiring or make repairs as required.
If no visible damage to wiring is found, prepare to perform resistance, continuity, ground integrity, and where applicable, reference voltage checks on all wiring. Be sure to disconnect all wiring from all relevant control modules to prevent damaging the controllers during resistance testing.
Compare all obtained readings with the values stated in the manual, and replace wiring or make repairs as required to ensure that all electrical values fall within the ranges specified by the manufacturer.
NOTE: Pay particular attention the internal resistance of both the actuator position sensor and the actuator itself if it is electrically operated. The internal resistance of these components is a reasonably good indicator of their overall condition, so replace components with OEM replacements if any resistance value does not agree with the specified value(s).
If the fault persists but all wiring and electrical values check out, use the scanner to cycle the clutch actuator multiple times to rule out an intermittent fault. However, be sure to monitor the current draw, since an excessive current draw could indicate either broken or worn clutch components, or a defective/ sticky actuator, and sometimes both.
NOTE #1: If the actuator is hydraulically operated and it has to be replaced, refer to the manual to determine the correct procedure to follow to remove and reinstall the replacement actuator without allowing air to enter the system. Purging air from a hydraulic system can sometimes be very challenging, so follow the instructions to the letter to avoid this problem.
NOTE #2: If a defective/sticky clutch actuator is suspected, replace both the actuator and the position sensor as a set to ensure that the PCM is supplied with accurate input data. Also bear in mind that on most applications, the new actuator and position sensor need to be adapted to the PCM by performing a prescribed adjustment and/or relearning procedure. Be sure to perform all required procedures EXACTLY as described in the manual to avoid a recurrence of the problem, or refer the vehicle to a competent repair facility for professional assistance with the relearning/adaptation procedure(s).
If the steps 1 through 4 did not resolve the problem, suspect either defects in clutch components, or a failed PCM. However, it is far more likely for the clutch to be defective than the PCM; if a defective clutch is suspected, refer the vehicle to the dealer or other competent repair facility for professional diagnosis and repair, since this type of diagnosis/repair requires removal of the transmission.
Codes Related to P0901
- P0900 – “Clutch Actuator Circuit/Open”
- P0902 – “Clutch Actuator Circuit Low”
- P0903 – “Clutch Actuator Circuit High”