C0402 code meaning
Rear Drive Clutch Solenoid Valve
What C0402 means
Publicly available J2012 tables skip C0402, yet GM assigns it in its rear differential clutch control module: the 2010–11 Saab 9-5 and the 2011 9-4X call it Transfer Case Solenoid Valve and describe the rear drive clutch solenoid, which the module drives by PWM to set the clutch pressure and so the torque sent rearward; the 2008–12 Saab 9-3 XWD calls it Differential Clutch Solenoid Valve. No maker documents it as a traction control lamp circuit. Subcode 02 is a short with coil resistance below 2 Ω, 04 an open with current off target by over 200 mA for 100 ms, 42/43/4B missing or bad calibration, 61 a valve that does not engage. AWD is switched off and Service Rear Axle appears; valve and module are replaced as a matched pair.
C0402 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0402
- Service Rear Axle or AWD warning displayed
- Car drives on the front wheels only
Common causes of C0402
- Most likelyOpen or shorted solenoid valve circuit at the rear drive unit
- PossibleValve calibration not stored after module replacement
- PossibleSolenoid valve sticking because of contaminated or aged clutch fluid
- Less likelyCorroded connector on the rear axle module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Clutch solenoidAwd control moduleAwd coupling
What each part of C0402 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 02 | The exact fault in that area. |
What to do next
- Note C0402 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 C0402
What does C0402 mean?
C0402 means "Rear Drive Clutch Solenoid Valve". Publicly available J2012 tables skip C0402, yet GM assigns it in its rear differential clutch control module: the 2010–11 Saab 9-5 and the 2011 9-4X call it Transfer Case Solenoid Valve and describe the rear drive clutch solenoid, which the module drives by PWM to set the clutch pressure and so the torque sent rearward; the 2008–12 Saab 9-3 XWD calls it Differential Clutch Solenoid Valve. It is a generic code, so it means the same on every make.
Is it safe to drive with C0402?
Drive gently and only to a workshop. With C0402 the car can go into limp mode (reduced power) to protect itself.
Will C0402 fail an emissions test?
C0402 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C0402 to fix?
Difficulty: hard. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will C0402 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.