P078D: Shift Timing Solenoid B High

What does P078D mean?

'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 (P0788: short to positive or overcurrent, on GM's Aisin-type unit above 1356 mA for 2 s). Warning lamp and limp mode follow; the opposite is P078C.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Warning lamp
• Limp mode

Common causes

• High Short to positive
• Medium Winding short

Likelihood is a general estimate across vehicles; your make and model may differ.