Powertrain, generic · Transmission

P078C Shift Timing Solenoid B Low

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). 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.

Likely causes

Wire open or shorted to ground

Coil open

Symptoms

Warning lamp
Limp mode

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€100–800

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

P078A P078D P0787

References: law.cornell.edu, gsi.ext.gm.com.