Powertrain, generic · Transmission
P088C Reverse Inhibit Control Circuit Low
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. P088C means the control line is shorted to ground, so the solenoid is energised unintentionally or can no longer be switched off.
Likely causes
Wire between engine module and gearbox chafed to ground (tunnel, near exhaust)
Solenoid coil shorted to ground
Water or corrosion in the gearbox connector
Engine module driver faulty
Symptoms
- Reverse cannot be engaged or is no longer 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
References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.