Faulty transmission mode switch B (internal short or worn contacts); Signal wire shorted to ground due to chafed or damaged wiring; Corroded, loose or water-damaged connector at the switch or control unit; Sticking or jammed switch or selector assembly, for example from spilt drink or debris; Poor reference voltage or earth supply to the switch circuit; Faulty transmission control module or a software fault, depending on the model.

P071E

Transmission Mode Switch B Circuit Low.

Generic
Powertrain
Generic code
Low severity

How this code is built

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

What it means

P071E is a generic powertrain code meaning the transmission control module has seen a low voltage signal on the Transmission Mode Switch B circuit. This is the driver-selected mode input (for example sport, economy, tow or snow, depending on the vehicle). The module sets the code when the signal sits below the expected range, which points to a short to ground, a faulty switch or a fault inside the circuit.

Symptoms

Gearbox warning light or malfunction indicator lamp on
Selected drive mode not recognised or not changing
Gearbox stuck in a default shift mode
Harsh, late or unusual gear changes
Mode indicator on the dash not matching the selection
Reduced performance or limp-home behaviour in some cases

Possible causes

Faulty transmission mode switch B (internal short or worn contacts)likely
Signal wire shorted to ground due to chafed or damaged wiringlikely
Corroded, loose or water-damaged connector at the switch or control unitpossible
Sticking or jammed switch or selector assembly, for example from spilt drink or debrispossible
Poor reference voltage or earth supply to the switch circuitpossible
Faulty transmission control module or a software fault, depending on the modelrare

How to diagnose

Read stored and pending codes and note the freeze frame data, then check for other gearbox or network codes.
Check the manufacturer's information for how the mode switch B circuit is arranged on this model, as the layout varies between vehicles and gearbox types.
Operate the mode switch through all positions and watch the live data to see whether the switch state changes or stays fixed low.
Inspect the switch, its surroundings and the wiring for contamination, damage, chafing or water ingress.
Check the connectors at the switch and control unit for corrosion, bent pins and poor terminal tension.
With the ignition off and the connector unplugged, test the signal wire for a short to ground and for continuity back to the control unit.
Check the reference voltage and earth at the switch against the manufacturer's specification.
If wiring and switch are sound, check for software updates relevant to this fault before considering the control unit.

How to fix

Replace the mode switch or the selector assembly it is part of if it tests faulty.
Repair or replace damaged wiring where it is shorted to ground.
Clean or repair corroded connectors and replace damaged terminals.
Clean or replace a contaminated or sticking switch assembly.
Restore a missing reference voltage or earth connection.
Update or replace the control unit only if testing confirms it is at fault, or if an outdated calibration is a known cause for this model.

Can I keep driving?

Low severity

The car can normally be driven, as the gearbox usually defaults to a standard mode. Book it in soon, and stop if shifting becomes harsh or the gearbox enters limp mode.

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