What it means
The transmission control module monitors the Shift Timing Solenoid B circuit for intermittent operation. It sets this code when the circuit signal or solenoid response drops out or becomes erratic during operation.
At a glance
- Usually lights the check-engine light
How it works
Shift timing solenoid B is an electrically controlled valve that helps the transmission time gear changes on its second shift-control channel. The TCM monitors its circuit and response; this code sets when the signal or solenoid response becomes erratic or drops out intermittently.
Common causes
Most likely first.
- Loose connector at the transmission
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Save the freeze-frame data and use live data to note when solenoid B's signal or response drops out, including gear, temperature, and vehicle vibration conditions.
- Inspect the solenoid B transmission connector and harness for loose fit, corrosion, chafing, or contact with a vibrating component.
- Move the harness and connector gently while monitoring the scan-tool data to look for an intermittent dropout.
- Test solenoid B circuit continuity and check for intermittent opens or shorts while flexing the harness, using the manufacturer's procedure.
- If the wiring passes, test solenoid B coil operation and the TCM command against the manufacturer's specification.
Common fixes
- Secure a loose solenoid B connector.
- Clean corroded terminals and restore a reliable connector fit.
- Repair chafed wiring and secure the harness away from vibration.
- Replace shift timing solenoid B if intermittent operation is confirmed.
- Repair the TCM driver only after the circuit and solenoid pass their checks.
Can I keep driving?
If shifts are predictable, use only short, gentle trips and avoid towing or hard acceleration. Stop if the transmission slips, shudders, or loses gears, since continued driving can worsen transmission damage.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.