Damaged, chafed, or corroded wiring in the clutch actuator B control circuit, including opens or shorts to ground; Failed clutch actuator B solenoid or motor, causing an open internal circuit; Loose or corroded electrical connector at the actuator or PCM; Blown fuse or faulty relay supplying power to the actuator circuit; Faulty PCM driver for the actuator control circuit, though this is less common; Contamination or fluid intrusion into the actuator connector causing high resistance

DTC codes / P09xx · Transmission / P090A

P090AClutch B Actuator Control Circuit/Open

Q: What does code P090A mean?

Clutch B Actuator Control Circuit/Open. P090A indicates that the powertrain control module (PCM) has detected an open circuit or loss of continuity in the control circuit for clutch actuator B, which is used in automated manual or dual-clutch transmissions to engage and disengage a clutch. The PCM monitors the circuit for expected voltage or current and sets this code when the signal falls outside the normal range, often disabling the actuator to protect the transmission.

P090A indicates that the powertrain control module (PCM) has detected an open circuit or loss of continuity in the control circuit for clutch actuator B, which is used in automated manual or dual-clutch transmissions to engage and disengage a clutch. The PCM monitors the circuit for expected voltage or current and sets this code when the signal falls outside the normal range, often disabling the actuator to protect the transmission.

SystemPowertrain

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaTransmission

Symptoms you may notice

Illumination of the check engine light or transmission warning light, often with no other symptoms besides the warning light
Harsh or delayed gear engagements, especially when starting from a stop or shifting between gears
Transmission may default to a limp-home mode, limiting engine power or preventing certain gears from being used
Inability to select gears or a flashing gear indicator on the instrument cluster
Audible clicking or no sound from the clutch actuator when attempting to shift
Vehicle may not move when placed in gear, or may experience sudden loss of drive

Common causes, most likely first

Damaged, chafed, or corroded wiring in the clutch actuator B control circuit, including opens or shorts to ground
Failed clutch actuator B solenoid or motor, causing an open internal circuit
Loose or corroded electrical connector at the actuator or PCM
Blown fuse or faulty relay supplying power to the actuator circuit
Faulty PCM driver for the actuator control circuit, though this is less common
Contamination or fluid intrusion into the actuator connector causing high resistance

How to diagnose and fix it

Perform a visual inspection of the actuator B wiring harness and connectors for damage, corrosion, or loose pins, and repair as needed
Check the fuse and relay for the clutch actuator circuit and replace any failed components
Use a digital multimeter to measure resistance and continuity of the control circuit from the PCM to the actuator, looking for opens or shorts
Test the clutch actuator B itself by applying power and ground directly to verify operation, and replace if it fails to actuate
Backprobe the PCM connector to check for the correct voltage or pulse-width modulated signal on the control circuit during activation
If all circuits and the actuator test good, suspect a faulty PCM and perform further diagnostics before replacement
Clear the code and perform a relearn or calibration procedure for the transmission as required by the manufacturer

What a P090A really tells you

An open circuit can be intermittent, so wiggle-test the harness while monitoring live data to catch a fault that only appears on rough roads or temperature changes.
A seized or mechanically binding clutch actuator can cause the PCM to set an open-circuit code by overheating the driver, so always check for mechanical freedom before replacing electrical parts.
The code often appears after transmission work or clutch replacement where a connector was left unplugged or a wire was pinched during reassembly.
Some vehicles use a shared power supply for multiple actuators, so a blown fuse may set P090A along with other actuator codes, pointing to a common feed rather than the actuator itself.
Do not overlook the ground circuit for the actuator; a poor ground can mimic an open circuit and cause the PCM to set this code even when the power side is intact.

Can I keep driving with P090A?

Driving with P090A is not recommended because the transmission may enter limp mode or lose the ability to engage gears, which can strand you or cause a loss of power in traffic. If you must move the vehicle, drive directly to a repair facility at low speed and avoid highways or heavy traffic.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.