P071B
Transmission Mode Switch A Circuit Low
Transmission
Generic OBD-II
High
What it means
P071B means the transmission mode switch — the control that selects between shift programs such as normal, sport, or tow/haul — is sending an abnormally low-voltage signal. This is a comfort/feature circuit, so the car generally starts and drives fine; you may simply lose the selectable mode or be locked into the default program. It usually points to the switch, a wiring short to ground, or a corroded connector.
High
Can I keep driving? Drivable — the car starts and drives normally; you may just lose a selectable mode (sport, tow/haul) or be stuck in the default shift program.
Common symptoms
What you'll notice
- Check-engine light on
- Sport, tow/haul, or other selectable mode not working
- Transmission stuck in its default shift program
- Mode indicator on the dash not responding
Common causes
Most likely first
- Faulty transmission mode switchLikely
- Short to ground in the mode switch circuitCommon
- Corroded or loose connector at the switchCommon
- Faulty control module (less common)Less often
How to diagnose & fix
Work through it in order
- Inspect the mode switch and its connector for corrosion or moisture intrusion.
- Check the switch circuit for a short to ground while operating the switch.
- Test the switch for correct resistance in each position.
- Replace the switch if it fails; suspect the control module only after wiring is verified. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P071B?+
Yes. This affects a selectable driving mode, not core transmission operation, so the car drives normally in its default program. Fix it to restore the mode.
Can I just clear P071B?+
It will return while the circuit reads low. The switch or its wiring short needs to be repaired for the code to stay off.
Related codes
Often seen with P071B
Read & clear P071B yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX