P0788 — Shift/Timing Solenoid High

The controller detects an input above the calibrated electrical range in the transmission shift/timing solenoid circuit. “High” describes the monitored signal level and does not by itself identify the faulty component or prove that the related physical quantity is high; circuit topology, reference values and thresholds are vehicle-specific.

Affected system: Transmission shift/timing solenoid control

Symptoms

• Warning light may illuminate
• Related system function may be impaired
• Vehicle-specific symptoms vary

Possible causes

• Transmission fluid, hydraulic, solenoid, connector, or control-circuit issue
• Related wiring, connector, power or ground fault
• Vehicle-specific mechanical or control issue

What to check

• Record stored and pending codes and freeze-frame data
• Compare commanded and actual transmission data, inspect fluid condition and level according to the vehicle procedure, then test the relevant circuit and solenoid.
• Confirm measured values against the vehicle service information
• Retest under the conditions that set the code
• Compare commanded and actual transmission data, inspect fluid condition and level according to the vehicle procedure, then test the relevant circuit and solenoid.
• Repair the verified cause and confirm the code does not return

Also written as: P0788-00, P078800, PO788 (some scan tools add the fault-type byte, e.g. -00).