What Does P0977 Mean?
The TCM has detected that the Shift Solenoid B (SS-B) control circuit voltage is consistently higher than expected, indicating a short to battery voltage or an open ground return. SS-B is stuck in one state because the TCM cannot pull the circuit low to command solenoid operation. This prevents normal gear transitions and the transmission will likely enter limp mode or be stuck in an unintended gear ratio.
Safety Warning
The transmission cannot shift normally and may be stuck in one gear or limp mode, significantly limiting vehicle capability. Avoid highway driving if the transmission cannot upshift. Have the vehicle diagnosed and repaired as soon as possible.
Common Causes
35%
Open ground return path in the SS-B circuit
25%
Short to battery voltage in the SS-B wiring harness
20%
Corroded or backed-out ground pin at the transmission case connector
15%
Shift Solenoid B with open winding on the ground side
5%
TCM SS-B driver circuit stuck in the high state
Diagnostic Steps
1
Measure SS-B resistance at the transmission connector — an extremely high or open reading suggests an open solenoid or broken ground-side winding.
2
With the transmission connector disconnected, check for battery voltage on the SS-B wire at the TCM connector with key on. Persistent voltage with no load suggests a short to B+ or a stuck-high TCM driver.
3
Verify continuity of the SS-B ground path from the solenoid through the internal harness, case connector, external harness, and back to the TCM ground reference. Any break causes the high reading.
4
Inspect the case connector for backed-out or corroded ground pins. Check all ground splices in the external harness.
5
If all tests pass, command SS-B on/off with the scan tool while monitoring circuit voltage at the TCM to confirm proper driver operation.
Estimated Repair Cost
$200 - $1,400
Parts + labor, varies by vehicle and location
The TCM has detected that the Shift Solenoid B (SS-B) control circuit voltage is consistently higher than expected, indicating a short to battery voltage or an open ground return. SS-B is stuck in one state because the TCM cannot pull the circuit low to command solenoid operation. This prevents norm...
The most common cause of P0977 (Shift Solenoid "B" Control Circuit High) is: Open ground return path in the SS-B circuit
Typical repair costs for P0977 range from $200 to $1,400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The transmission cannot shift normally and may be stuck in one gear or limp mode, significantly limiting vehicle capability. Avoid highway driving if the transmission cannot upshift. Have the vehicle diagnosed and repaired as soon as possible.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0977 to identify the root cause.
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Quick Info
Category
Powertrain
System
Automatic Transmission / Transaxle
Difficulty
Type
Generic (SAE)
Recommended Tools
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