Powertrain, generic · Transmission

P0977 Shift Solenoid B Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

High-voltage fault in the control circuit of shift solenoid B. GM six-speeds put an open or a power short of the mode 3 multiplex valve here, 1.2 of 1.5 s; the 2016 table sets it without MIL, the 2019 table with MIL after one trip. The Saab 9-4X 6T70 treats it more severely than P0976: 2 s, Type A, high-side driver off, only reverse and 5th gear left, no converter lockup. Ford uses it strictly for SSB short to power, as in its 2012 and later summaries. GM's Allison 1000 checks for 0.39 ohm or less to a supply over three samples (75 ms in 2016, 60 ms in 2023). FCA 9-speed and Aisin uses are not documented for this code. Ground-side faults are P0976.

Likely causes

Open solenoid B coil or wire on GM six-speeds, where opens report as high
Control wire shorted to battery or a switched supply
Damaged pins or seals at the transmission pass-through connector
Faulty driver stage in the control module

Symptoms

  • Limp mode with only reverse and one high forward gear
  • Weak acceleration from rest
  • MIL or transmission warning, depending on calibration

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,600
Time1–5 h

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

Parts involved

shift solenoid bwiring harnesstcm

Related codes

P0976P097BP0975P0755P0757

References: gsi.ext.gm.com, gsi.ext.gm.com, newtonnet.co.uk, saabwisonline.com.