P078A code meaning
Shift Timing Solenoid B
Powertrain system Generic code P07xx codes Check engine light
What P078A 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). P078A is the general circuit code for solenoid B. The only documented user is Hyundai/Genesis: on the 2017–18 G80/G90 with shift-by-wire it is the on/off solenoid that engages reverse. The bulletins replace valve and electronic module, then the transmission module if the code returns. Reverse may not engage, with warning lamp and limp mode.
P078A 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 P078A
- Warning lamp
- Reverse cannot be engaged (Genesis shift-by-wire)
- Limp mode
Common causes of P078A
- Most likelySolenoid faulty
- PossibleElectronic module or transmission module
- Less likelyConnector or wire
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 P078A 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. |
| 8A | The exact fault in that area. |
What to do next
- Note P078A 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 P078A
What does P078A mean?
P078A means "Shift Timing Solenoid B". '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 P078A?
Drive gently and only to a workshop. With P078A the car can go into limp mode (reduced power) to protect itself.
Will P078A fail an emissions test?
Yes, it can. P078A 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 P078A to fix?
Difficulty: medium. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will P078A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.