P28CB code meaning
Clutch A Motor Position Sensor Circuit/Open
Powertrain system Generic code P28xx codes Check engine light
What P28CB means
A brushless motor can only be commutated correctly if the electronics know where the rotor stands; P28CB reports that the signal from the sensor tracking the clutch A motor's rotor position is missing or electrically unusable, mostly through an open line. Without it the controller cannot switch the U-V-W phases in the right order or count motor revolutions, so the pump of clutch A is shut down. In Getrag-type pump actuators these brushless ferrite motors are shared parts, and the position signal also serves to check motor speed against the pressure target. Typical causes: an open sensor feed or ground, a corroded pin, a failed sensor element. P28CC covers a signal that is present but implausible. No manufacturer publishes P28CB details.
P28CB at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P28CB
- Clutch A disabled, gears on that shaft unavailable
- Transmission warning lamp
- Possibly also motor speed codes stored
Common causes of P28CB
- Most likelyOpen signal, supply or ground wire of the clutch A motor position sensor
- PossibleCorroded or loose pin at the actuator connector
- PossibleFailed position sensor inside the actuator
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Clutch motor position sensor aWiring harnessTCM
What each part of P28CB means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 8 | Area: transmission. |
| CB | The exact fault in that area. |
What to do next
- Note P28CB and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P28CB
What does P28CB mean?
P28CB means "Clutch A Motor Position Sensor Circuit/Open". A brushless motor can only be commutated correctly if the electronics know where the rotor stands; P28CB reports that the signal from the sensor tracking the clutch A motor's rotor position is missing or electrically unusable, mostly through an open line. It is a generic code, so it means the same on every make.
Is it safe to drive with P28CB?
Drive gently and only to a workshop. With P28CB the car can go into limp mode (reduced power) to protect itself.
Will P28CB fail an emissions test?
Yes, it can. P28CB is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P28CB to fix?
Difficulty: hard. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P28CB clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.