P0788 Shift/Timing Solenoid High

P0788 points to a high shift or timing solenoid circuit signal. The module sees excessive voltage or an open/high circuit condition.

Code details

Generic OBD-II · P0

System: Transmission
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not treat a high circuit code as a hydraulic failure until the electrical path has been loaded and tested.

Symptoms of P0788

Harsh, delayed, or slipping shifts, or being stuck in one gear.
Check-engine light, sometimes with limp-home mode.
Flaring RPM or a shudder under load.

Common causes of P0788

Low or degraded transmission fluid.
A failing speed sensor, shift solenoid, or pressure-control circuit.
Wiring, connector, or internal hydraulic/mechanical faults.

Useful checks before replacing parts

Measure solenoid circuit voltage, resistance, feed voltage, driver control, and connector continuity under loaded conditions.
Inspect for open circuits, short-to-voltage faults, connector spread, internal harness damage, and module connector corrosion.
Compare command state with shift timing and ratio data to confirm whether the high circuit changes transmission behavior.

Related OBD-II codes

These nearby transmission entries can help compare wording and pin down the fault area.