Faulty mode switch (worn contacts, sticking or internal failure); Damaged, corroded or loose wiring or connector in the switch circuit; Moisture, spilled drink or dirt contamination in the switch or console area; Short to earth, short to voltage or open circuit in the signal or reference wire; Poor earth or low supply voltage to the switch or control unit; Faulty transmission control unit or related control module; Outdated control unit software where the manufacturer has a known fix for the model.

P071A

Transmission Mode Switch A Circuit.

Generic
Powertrain
Generic code
Low severity

How this code is built

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

What it means

P071A is the generic code for a fault in the Transmission Mode Switch A circuit. The transmission control unit monitors the signal from the driver-operated mode switch (such as sport, economy, snow or tow/haul, depending on the vehicle). It set the code because the signal was out of range, stuck, erratic or did not match what it expected. Which mode the switch selects and how it is wired varies by model.

Symptoms

Transmission warning light or malfunction indicator lamp on
Selected drive mode does not engage or does not change
Mode indicator on the dash flickers, is wrong or is missing
Gearshifts feel different from normal, such as stuck in a default shift pattern
Gearbox may revert to a default or limp strategy on some models

Possible causes

Faulty mode switch (worn contacts, sticking or internal failure)likely
Damaged, corroded or loose wiring or connector in the switch circuitlikely
Moisture, spilled drink or dirt contamination in the switch or console areapossible
Short to earth, short to voltage or open circuit in the signal or reference wirepossible
Poor earth or low supply voltage to the switch or control unitpossible
Faulty transmission control unit or related control modulerare
Outdated control unit software where the manufacturer has a known fix for the modelrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, then check for other transmission, network or voltage faults
Operate the mode switch and watch whether the dash indicator and any live data for switch state change correctly
Visually inspect the switch, its surround and the console for damage, moisture or spilled liquid
Inspect the switch connector and the control unit connector for corrosion, bent or pushed-out pins and poor tension
Check the battery voltage and the charging system, as low voltage can cause false switch faults
With the wiring diagram for the model, test the switch circuit for supply, signal, earth, continuity and shorts
Test the switch itself for correct resistance or continuity in each position against the manufacturer specification
Check for technical service bulletins or software updates for the vehicle before considering the control unit

How to fix

Replace the mode switch if it fails testing or is mechanically worn
Repair or replace damaged wiring and clean or replace corroded connectors
Dry out and clean the switch area, and replace the switch if moisture has damaged it
Restore proper earth and power supply connections
Update the control unit software only if the manufacturer lists it as a fix for this fault
Replace or repair the control unit only after all wiring and switch checks have been passed

Can I keep driving?

Low severity

The car can normally be driven, as the transmission usually keeps working in a default mode, but book it in soon. If the gearbox goes into limp mode, shifts harshly or the warning lights stay on, have it checked sooner.

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