P078C code meaning
Shift Timing Solenoid B Low
Powertrain system Generic code P07xx codes Check engine light
What P078C means
'Shift timing solenoid' means different parts: on GM's 4L60-E the 3-2 downshift solenoid that times the band apply on that downshift, on Aisin five-speeds (GM, Saab) the linear valve SLS that sets clutch pressure during the shift, and on the 2017–18 Genesis G80/G90 with shift-by-wire the on/off solenoids that engage drive (A) and reverse (B). Only Hyundai/Genesis is documented using solenoid B, and only with the base code P078A. No manufacturer document available to us uses this code; the description follows solenoid A (P0787: open circuit or short to ground, on GM's 4L60-E more than 43 of 50 failed counts). Warning lamp and limp mode follow; the opposite is P078D.
P078C at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P078C
- Warning lamp
- Limp mode
Common causes of P078C
- Most likelyWire open or shorted to ground
- Most likelyCoil open
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Shift timing solenoidTransmission wiringTransmission control module
What each part of P078C means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7 | Area: transmission. |
| 8C | The exact fault in that area. |
What to do next
- Note P078C 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 P078C
What does P078C mean?
P078C means "Shift Timing Solenoid B Low". 'Shift timing solenoid' means different parts: on GM's 4L60-E the 3-2 downshift solenoid that times the band apply on that downshift, on Aisin five-speeds (GM, Saab) the linear valve SLS that sets clutch pressure during the shift, and on the 2017–18 Genesis G80/G90 with shift-by-wire the on/off solenoids that engage drive (A) and reverse (B). It is a generic code, so it means the same on every make.
Is it safe to drive with P078C?
Drive gently and only to a workshop. With P078C the car can go into limp mode (reduced power) to protect itself.
Will P078C fail an emissions test?
Yes, it can. P078C 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 P078C to fix?
Difficulty: medium. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will P078C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.