Powertrain, generic · Transmission

P088D Reverse Inhibit Control Circuit High

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

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

Symptoms

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

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–350
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

reverse lockout solenoidsolenoid wiringengine control modulemanual transmission

Related codes

P0801P088CP0803P080DP0813

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.