Open circuit, chafed wiring or damaged connector in the reverse inhibit solenoid circuit; Faulty reverse inhibit solenoid or actuator; Corroded or loose connector terminals, or poor earth connection; Blown fuse or fault in the power supply to the circuit; Faulty gear selector or shift lock mechanism, or related switch; Fault inside the control unit driver, or outdated software where the manufacturer has issued a fix.

P0801

Reverse Inhibit Control Circuit/Open.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
8: AreaTransmission
01: FaultThe specific fault in that area

What it means

P0801 is the generic code for a fault in the reverse inhibit control circuit. On vehicles that fit this feature, the reverse inhibit solenoid or circuit stops the gearbox being shifted into reverse by mistake at speed or in certain conditions. The control unit set the code because it saw an open circuit, or a circuit that did not respond as commanded, on the reverse inhibit control line.

Symptoms

Reverse gear will not engage, or engages only intermittently
Reverse gear engages when it should be blocked, or the lock feels stuck
Gear lever feels unusually stiff or loose when selecting reverse
Reverse lights not working correctly on some models
Malfunction indicator lamp on, sometimes with a gearbox warning light

Possible causes

Open circuit, chafed wiring or damaged connector in the reverse inhibit solenoid circuitlikely
Faulty reverse inhibit solenoid or actuatorlikely
Corroded or loose connector terminals, or poor earth connectionpossible
Blown fuse or fault in the power supply to the circuitpossible
Faulty gear selector or shift lock mechanism, or related switchpossible
Fault inside the control unit driver, or outdated software where the manufacturer has issued a fixrare

How to diagnose

Read all stored codes and freeze frame data, and note any other gearbox or network codes
Check the relevant fuses and look up the circuit layout for this model, as the layout and component location vary by vehicle
Visually inspect the wiring and connector at the reverse inhibit solenoid for chafing, water ingress, corrosion and bent or pushed-back pins
Operate the gear selector through reverse and listen and feel for the solenoid or lock working
Check the supply voltage and earth at the solenoid connector with the ignition on
Test the solenoid winding resistance against the manufacturer's specification and check the control wire for continuity and shorts to earth or supply
Command the solenoid with a suitable diagnostic tester, if supported, and compare the response with the commanded state
Check for applicable software updates or technical bulletins for the model before condemning the control unit

How to fix

Repair or replace damaged wiring and clean or renew faulty connector terminals
Replace the reverse inhibit solenoid or actuator if it fails electrical or operating tests
Restore the power supply or earth, and replace any blown fuse once the cause of the overload is found
Repair or replace the gear selector or shift lock components if they are faulty
Update the control unit software if a known fault is fixed by a newer calibration, or replace the control unit if it is confirmed faulty

Can I keep driving?

Medium severity

The car can usually be driven carefully, but reverse may not engage or may not be properly inhibited, which can be inconvenient and, in some cases, a risk to the gearbox. Get it checked soon, and take extra care when manoeuvring.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.