P0977: Shift Solenoid “B” Control Circuit High OBD-II Trouble Code

Every time your transmission changes gears, a little plunger mechanism known as a solenoid, directs pressurized transmission fluid down the right channel to move the gears and clutches. If the ECU detects an unusually high-voltage signal along this shift solenoid B control circuit, a P0977 DTC will be saved.

Need a replacement transmission? Get an estimate for replacement transmissions and local installation. Look up your transmission model by vehicle make and model.

What Transmission Do I Have?

How Serious is the Code?

If the computer is not able to control a shift solenoid, then the transmission will not function properly. The transmission problems related to a P0977 diagnostic trouble code may start out as barely noticeable, but they will continue to get worse. Eventually leading to a nonfunctioning transmission.

Symptoms

Symptoms of a P0977 include:

  • Hard gear changes
  • Transmission may not shift into gear

Causes

  • Dirty transmission fluid/filter
  • Low on transmission fluid
  • Damaged wiring
  • Corroded/broken connectors
  • The shift solenoid has broken

How to Diagnose the Code?

The condition and level of transmission fluid is the first thing that should be checked when trying to diagnose a P0977 OBDII trouble code. If it’s clean and at the proper level, the wiring and connectors along the transmission wiring harness should be checked for signs of damaged wiring, and/or corroded/broken connectors. If everything is checked out of this point, then the shift solenoid itself will need to be tested.

Need a replacement transmission? Get an estimate for replacement transmissions and local installation. Look up your transmission model by vehicle make and model.

What Transmission Do I Have?

What Repairs Will Fix P0977?

  • Service the transmission
  • Replace or repair damage wiring/connectors
  • Replace shift solenoid

Related Codes

  • P0975 – Shift Solenoid “B” Control Circuit Range/Performance
  • P0976 – Shift Solenoid “B” Control Circuit Low