P0789 Shift/Timing Solenoid Intermittent

P0789 indicates an intermittent shift or timing solenoid fault. The circuit or response disappears, spikes, or becomes invalid only sometimes.

Code details

Generic OBD-II · P0

System: Transmission
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not clear intermittent solenoid timing codes without trying to reproduce the exact failure conditions.

Symptoms of P0789

Harsh, delayed, or slipping shifts, or being stuck in one gear.
Check-engine light, sometimes with limp-home mode.
Flaring RPM or a shudder under load.

Common causes of P0789

Low or degraded transmission fluid.
A failing speed sensor, shift solenoid, or pressure-control circuit.
Wiring, connector, or internal hydraulic/mechanical faults.

Useful checks before replacing parts

Graph solenoid command, circuit feedback, ratio change, speed sensor data, and fluid temperature during repeatable driving.
Inspect terminal tension, internal harness movement, case connector condition, heat sensitivity, and vibration-related wiring faults.
Check whether the intermittent event aligns with one shift, a hot soak, road vibration, or a specific throttle range.

Related OBD-II codes

These nearby transmission entries can help compare wording and pin down the fault area.