BMW fault 4E89 - Solenoid valve S2
P0977 · Control circuit high
4E89 is stored by the EGS when shift solenoid S2 (shift solenoid B) remains energized after being commanded off. This solenoid directs pressurized fluid to specific clutch packs in the transmission valve body. A stuck-on solenoid prevents the controlled release of hydraulic pressure during gear changes.
The EGS commands solenoid S2 to deactivate but receives feedback indicating the solenoid remains energized. The fault is logged after the solenoid is triggered 5 times for 100 ms periods with OFF status but consistently returns ON feedback. This indicates a short to power in the wiring, a mechanically stuck plunger, or a driver circuit stuck in the on state. Monitoring requires the engine running and battery voltage between 9V and 16V. The MIL illuminates on the second drive cycle.
- Module
- EGS
- Severity
- Warning
- Likely cause
- Short to power in the solenoid S2 wiring
- Common fix
- Repairing the transmission wiring harness
Symptoms
- MIL (check engine light) illuminated.
- Harsh or erratic gear shifts as the solenoid fails to release hydraulic pressure on command.
- Transmission enters failsafe mode.
Common causes
- Short to battery voltage in the external transmission wiring harness where the S2 control wire contacts a power source.
- Moisture or contamination in the connector bridging the S2 control pin to an adjacent supply pin.
- Short circuit in the internal transmission wiring harness (14-pin) between the solenoid control wire and a powered circuit.
- EGS control module driver circuit stuck in the on state.
Diagnosis
- Read the fault memory and determine whether the fault is active or stored. If passive, check plug connections at the EGS and transmission for correct engagement, loose contacts, and any corrosion bridging pins. Inspect the external harness for damaged insulation or bare copper contacting powered wires. Check specifically for shorts to battery positive.
- If the fault is active, disconnect the EGS connector and measure voltage on the solenoid S2 control pin. Any voltage present with the EGS disconnected confirms a short to power in the harness.
- If the external harness is clear, measure resistance on the internal 14-pin harness. Check for shorts between the solenoid S2 control wire and adjacent power supply wires. Low resistance between them confirms an internal harness short.
- If all wiring checks pass, the solenoid plunger may be mechanically stuck, or the EGS control module driver circuit is faulty. Replace the internal harness if resistance is out of specification, or replace the solenoid if the plunger is stuck. Verify the EGS output if all else passes.
Resolution
Repair the external wiring harness if a short to power is found, and reroute any wires contacting power sources. Replace the internal 14-pin harness if an internal short is confirmed. If the solenoid plunger is stuck, replace the solenoid or hydraulic actuator. As a last resort, replace the EGS control module if the driver circuit is faulty, and reset adaptation data after replacement. Clear the fault memory and confirm the MIL does not return over two full drive cycles.