Powertrain, generic · Transmission

P078A Shift Timing Solenoid B

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

'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.

Likely causes

Solenoid faulty
Electronic module or transmission module
Connector or wire

Symptoms

  • Warning lamp
  • Reverse cannot be engaged (Genesis shift-by-wire)
  • Limp mode

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€200–1,000
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

shift timing solenoidtransmission wiringtransmission control module

Related codes

P0785P078BP078CP078DP078E

References: static.nhtsa.gov, static.nhtsa.gov.