P0787: Shift Timing Solenoid A Low

What does P0787 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). P0787 means current or voltage in the circuit is too low – an open circuit or short to ground. GM's 4L60-E checks the 3-2 downshift solenoid output (more than 43 of 50 counts) after one trip and then sets maximum line pressure, holds third gear and disables the converter clutch; GM's Aisin-type five-speed flags SLS current below 92 mA for 12.5 s. The opposite is P0788.

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

Symptoms

• Warning lamp
• Limp mode (GM: fixed third gear)
• Harsh shifts from maximum pressure

Common causes

• High Wire open or shorted to ground
• High Solenoid coil open
• Low Module driver stage

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