Powertrain, generic · Transmission

P071A Transmission Mode Switch A Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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. P071A is the general circuit fault of mode switch A: its state is invalid or implausible. The transmission then usually stays on its normal schedule. Low and high are P071B/P071C, switch B has P071D–P071F; the range sensor (PRNDL) is P0705 ff.

Likely causes

Mode switch A faulty (selector lever or console)
Wiring or connector in the console damaged (spilled drinks, chafing)
Resistor coding drifted (analog buttons)
Control module faulty

Symptoms

  • Mode A cannot be selected or stays active
  • Mode indicator missing or flashing
  • Transmission stays on the normal shift schedule

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–300
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

transmission mode switchswitch wiringtransmission control module

Related codes

P071BP071CP071DP0700P0705

References: law.cornell.edu, gsi.ext.gm.com.