P071B code meaning
Transmission Mode Switch A Circuit Low
What P071B means
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.
P071B at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P071B
- Mode A cannot be selected or stays active
- Mode indicator missing or flashing
- Transmission stays on the normal shift schedule
Common causes of P071B
- Most likelySignal wire shorted to ground
- PossibleButton stuck pressed (switching to ground)
- PossibleMoisture or dirt in the button
- Less likelyControl module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Transmission mode switchSwitch wiringTransmission control module
What each part of P071B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 7 | Area: transmission. |
| 1B | The exact fault in that area. |
What to do next
- Note P071B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P071B
What does P071B mean?
P071B means "Transmission Mode Switch A Circuit Low". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P071B?
P071B does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P071B fail an emissions test?
P071B is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P071B to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P071B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.