A transmission mode switch selects an alternative shift schedule such as sport, winter or tow/haul; J2012 does not define which button is A or B. No manufacturer document available to us uses P071A–P071F: GM monitors its analog drive mode switch under its own codes (low below 21–29 % of 5 V, high from 94 %, 200 of 250 samples, two trips), which shows how such buttons are read as coded voltages. P071B means the signal of mode switch A is below its lower limit: with analog, resistor-coded buttons a short to ground, with digital buttons switching to ground a button stuck pressed. The opposite is P071C.
Medium severity. Can I keep driving?Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
Symptoms
- Mode A cannot be selected or stays active
- Mode indicator missing or flashing
- Transmission stays on the normal shift schedule
Most likely causes
- Signal wire shorted to ground
- Button stuck pressed (switching to ground)
- Moisture or dirt in the button
- Control module faulty
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: easy
What each character of P071B means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 7: Transmission
- 1B: Specific fault in that system
Frequently asked questions
Can I keep driving with code P071B?
Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
What causes code P071B?
The most common causes are: signal wire shorted to ground; button stuck pressed (switching to ground); moisture or dirt in the button.
Related codes
- P071ATransmission Mode Switch A Circuit
- P071CTransmission Mode Switch A Circuit High
- P071ETransmission Mode Switch B Circuit Low
- P0700Transmission Control System (MIL Request)
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.