Faulty transmission mode switch or selector assembly (internal open circuit or fault, worn or contaminated contacts); Open circuit or high resistance in the switch signal wiring, or corroded or loose connector terminals; Signal wire shorted to a voltage supply; Poor or missing switch ground connection; Moisture or liquid ingress into the switch, shifter or connector (for example a spilt drink); Faulty transmission control module or related control unit, or an outdated calibration where the manufacturer lists it as a known cause.

P071C

Transmission Mode Switch A Circuit High.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
7: AreaTransmission
1C: FaultThe specific fault in that area

What it means

P071C is a generic code meaning the transmission control module has detected a high voltage in the Transmission Mode Switch A circuit. The module saw a signal voltage above the expected range, which usually points to an open circuit, a short to voltage or a faulty switch. The exact switch type, location and signal strategy depend on the make, model and gearbox.

Symptoms

Gearbox mode selection (such as sport, economy, winter or tow/haul) not working or not responding
Mode indicator on the dash missing, flashing or showing the wrong mode
Gearbox stuck in a default mode with changed shift points
Harsh, delayed or unusual gear changes
Gearbox or gearbox warning light on, with the engine light possibly on too

Possible causes

Faulty transmission mode switch or selector assembly (internal open circuit or fault, worn or contaminated contacts)likely
Open circuit or high resistance in the switch signal wiring, or corroded or loose connector terminalslikely
Signal wire shorted to a voltage supplypossible
Poor or missing switch ground connectionpossible
Moisture or liquid ingress into the switch, shifter or connector (for example a spilt drink)possible
Faulty transmission control module or related control unit, or an outdated calibration where the manufacturer lists it as a known causerare

How to diagnose

Read all stored codes and freeze frame data, noting when the fault set and whether other transmission or network codes are present
Check for manufacturer service bulletins for the specific model and gearbox
Operate the mode switch and watch the live data for the switch state or signal voltage, checking it changes with each press
Visually inspect the switch, shifter area and connectors for damage, moisture, corrosion or spilt liquid
Check the wiring between the switch and control module for chafing, breaks and pin damage, and wiggle test it while watching live data
With the switch unplugged, check the reference voltage, signal and ground against the wiring diagram for that model
Test the wiring for a short to voltage and check continuity and resistance of the signal and ground circuits
Check the switch resistance or operation against the manufacturer's specification before condemning the control module

How to fix

Replace the mode switch or selector assembly if it fails testing
Repair or replace damaged wiring and clean or replace corroded connector terminals
Repair any short to voltage in the signal circuit
Restore a good ground connection to the switch
Dry out and clean the switch and connector after liquid ingress, replacing parts that are damaged
Repair or replace the control module, or update its calibration, only after the wiring and switch are proven good and the manufacturer's procedure calls for it

Can I keep driving?

Low severity

The car can usually be driven, but the gearbox may stay in a default mode with altered shifting. Book it in soon, and stop driving if the gearbox shifts harshly, slips or goes into limp mode.

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