P088D: Reverse Inhibit Control Circuit High

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.

Symptoms

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

Most likely causes

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

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the fluid level and condition
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Read the input and output speed in live data
4. Check the connector and wiring
5. Check for other related engine codes
6. Consult the manufacturer's procedure for the transmission

Good to know

• Repair difficulty: medium

What each character of P088D means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 8: Transmission
• 8D: Specific fault in that system

Frequently asked questions

Can I keep driving with code P088D?

Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.

What causes code P088D?

The most common causes are: control wire shorted to a supply wire in the harness; solenoid coil low-resistance or shorted (driver overcurrent); moisture or corrosion between supply and control pin.

Related codes

• P0801Reverse Inhibit Control Circuit/Open
• P088CReverse Inhibit Control Circuit Low
• P0803Upshift/Skip Shift Solenoid Control Circuit
• P080DUpshift/Skip Shift Solenoid Control Circuit High
• P0813Reverse Output Circuit

Sources

• gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
• gsi.ext.gm.com: 19OBDG03A Diagnostics
• gsi.ext.gm.com: 19OBDG03B Diagnostics
• gsi.ext.gm.com: 16OBDG07A Engine Diagnostics

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.