P088D: Reverse Inhibit Control Circuit High

What does P088D mean?

The reverse inhibit solenoid on GM's six-speed manual gearboxes (Corvette, Camaro, CTS-V, ATS-V) blocks reverse while driving forward and is released by the engine module. A low-side driver with built-in diagnosis watches the control line: above 9 V and 250 rpm, 20 faults in 25 samples of 250 ms (about 6 s) set the code. GM rates it type C without MIL; from 2019 a service message appears. P0801 is the open circuit. P088D means the control line is shorted to voltage: when the driver switches on it sees too high a level or overcurrent, and the solenoid can no longer be operated, so reverse may stay locked.

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

Symptoms

• Reverse cannot be engaged (lockout not released) or is not blocked
• Service message (GM from 2019), no MIL

Common causes

• High Control wire shorted to a supply wire in the harness
• Medium Solenoid coil low-resistance or shorted (driver overcurrent)
• Medium Moisture or corrosion between supply and control pin
• Low Engine module driver faulty

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