P0978 code meaning
Shift Solenoid C Control Circuit Range/Performance
Powertrain system Generic code P09xx codes Check engine light
What P0978 means
Range/performance fault in the drive circuit of shift solenoid C. GM's 2007 Allison 1000 table used it for an open SS3 circuit, but only while the commanded gear is not reverse trim, 5th or 6th; the table even prints the label Circuit Low beside an open-circuit test, an apparent typo. FCA lists P0978 among the four codes that the 2014–2016 9-speed transaxle set under old software when the range sensor harness had poor crimps. Ferrari's DCT bulletin uses it for a missing signal from the actuator 4 engage position sensor. Ford and GM six-speeds do not use it. Low/high are P0979/P0980, the current open code P097C.
P0978 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0978
- MIL or transmission warning on
- Sudden neutral or default gear while driving
- Erratic or missing shifts
Common causes of P0978
- Most likelyIntermittent high resistance at crimped harness terminals (FCA 9-speed)
- PossibleOpen coil of shift solenoid C (Allison-type usage)
- PossibleTransmission software that predates the manufacturer's fix
- Less likelyFaulty driver stage in the transmission control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Shift solenoid cWiring harnessTCM
What each part of P0978 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 9 | Area: transmission. |
| 78 | The exact fault in that area. |
What to do next
- Note P0978 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 P0978
What does P0978 mean?
P0978 means "Shift Solenoid C Control Circuit Range/Performance". Range/performance fault in the drive circuit of shift solenoid C. It is a generic code, so it means the same on every make.
Is it safe to drive with P0978?
Drive gently and only to a workshop. With P0978 the car can go into limp mode (reduced power) to protect itself.
Will P0978 fail an emissions test?
Yes, it can. P0978 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 P0978 to fix?
Difficulty: hard. A typical repair takes 0.5 to 5 hours of work. This is a job for a workshop.
Will P0978 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.