P0902: Clutch actuator circuit voltage too low
Clutch actuator circuit low (semi-automatic transmission)
Severity: Inspect soon
TroubleCodes.net says P0902 can leave the car unable to engage a gear and possibly undrivable, and PartsAvatar describes the same circuit fault.
It gets more serious if:
- Not verified: The engine stalls or the car will not move or crank. We found no source saying whether to keep driving.
P0902 in short
P0902 means the computer sees too little voltage in the clutch actuator circuit on a semi-automatic or dual-clutch transmission. The selector switch, wiring or the actuator are the usual causes. The car may fail to engage a gear, stall or enter limp mode, so have it inspected soon.
Semi-automatic and dual-clutch transmissions use an actuator, a motor or hydraulic solenoid, to press and release the clutch instead of a pedal. The computer watches that circuit and sets P0902 when its voltage is lower than it should be.
TroubleCodes.net says the selector switch is the most common cause, then wiring, a short to ground and the actuator. On hydraulic systems, low brake fluid can also play a part, and a module fault is rare.
Because the car may not engage a gear, treat this as a fault to get looked at soon. Read both the engine and transmission modules before anything is cleared.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Gear selector or shift switch fault
Common general cause- Why it ranks here
- TroubleCodes.net lists the selector switch as the most common cause.
- What would change this
- Rises if gear engagement worsens with shifter movement.
Cause 2: Wiring, ground or short to ground in the actuator circuit
Common general cause- Why it ranks here
- Both sources list wiring faults, an open circuit or a ground problem, and a low-voltage code points at the circuit.
- What would change this
- Rises if the harness is chafed or a ground connection is loose or corroded.
Cause 3: Failed clutch actuator motor or solenoid
Common general cause- Why it ranks here
- Both sources list the actuator or solenoid.
- What would change this
- Rises if wiring and selector test good and the actuator does not respond.
Cause 4: Low brake or clutch fluid on hydraulic systems
Common general cause- Why it ranks here
- TroubleCodes.net lists low brake fluid for hydraulic clutch systems.
- What would change this
- Rises if the reservoir is low. Low fluid also means a leak to find.
Cause 5: Transmission control module
Possible — needs testing- Why it ranks here
- Both sources list the module as a rare cause.
- What would change this
- Rises only after everything else is ruled out.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read codes from the engine and transmission modules with a scan tool that supports both, before anything is cleared. Note any selector, clutch position or other circuit codes.
IfSelector or shift switch codes are stored
It meansStart with the selector.
IfP0902 alone
It meansCheck the fluid and wiring.
Step 2: If the clutch is hydraulic, look at the fluid reservoir level by the maker's method.
Warning:The brake and clutch systems may share fluid. Low fluid can affect braking, so have a leak checked before driving.
IfThe level is low
It meansFind the leak first. Do not just top it up.
IfThe level is normal or the system is not hydraulic
It meansInspect the wiring.
Step 3: Inspect the actuator connector, harness and ground points for chafing, corrosion and loose connections.
IfDamage or a loose ground is found
It meansRepair it and retest.
Points to: Wiring, ground or short to ground in the actuator circuit
IfEverything looks fine
It meansA shop should test the actuator and circuit.
Step 4: Have a shop check circuit voltage and command the actuator with a scan tool.
Warning:Shop test. It needs the maker's wiring diagram.
IfThe circuit is good but the actuator does not respond
It meansThe actuator has failed.
IfVoltage is low at the actuator
It meansTrace the wiring and ground.
Points to: Wiring, ground or short to ground in the actuator circuit
Symptoms
- Check engine light
- Cannot engage a gear
- Engine stalls Gets more serious: stop and have it checked.
- Limp mode, or no crank Gets more serious: stop and have it checked.
How to fix
Step 1: Do not clear the code before the transmission module has been read.
Step 2: Look for fluid leaks under the car if the system is hydraulic.
Parts and cost context
- Transmission control module (TCM):Do not replace the module for P0902 unless a test points to it. Both sources call a module fault rare.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
We don't have reviewed vehicle-specific evidence for P0902 yet. The causes and tests above apply across vehicles.
Related codes
No curated relationships for P0902 yet.
P0902 questions
Which cars set P0902?
Cars with a semi-automatic or dual-clutch transmission, where an actuator works the clutch. Cars with a normal automatic or a clutch pedal do not use this circuit.
Can I drive with P0902?
It may not be possible. The car may not engage a gear, may stall or may not crank. Have it inspected soon.
Sources and review
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error