P0789 Code: Meaning, Symptoms, Causes & Fix

Overview

P0789 is triggered when monitoring logic identifies an issue with Shift Timing Solenoid A Intermittent affecting engine synchronization and valve timing.

Symptoms

loss of power at mid/high RPM
engine noise or unstable timing
rough running or misfire

Common causes

Intermittent harness contact affecting shift timing solenoid a intermittent
Connector pin fit issue
Connector pin damage/corrosion or harness stress near related components

How to diagnose P0789

Confirm P0789 and capture freeze-frame data with a professional scan tool.
Inspect wiring, connectors, and grounds related to shift timing solenoid a intermittent for obvious defects.
Reproduce the fault with harness movement and heat/vibration checks.
Check for related DTCs to identify the root-cause chain before replacing parts.
After repair, clear codes and confirm readiness monitors complete without recurrence.

Severity of code P0789

Moderate: This code is moderate severity: the vehicle may still operate, but fault progression can increase repair cost over time.

Can you drive with P0789?

Most vehicles can be driven short-term with P0789, but postpone heavy load/highway driving until repaired.

If the warning lamp is flashing or drivability/safety is affected, avoid driving and diagnose immediately.

How to fix it (step-by-step)

Repair obvious wiring/connector faults first to prevent repeat parts replacement.
Address the root fault mode (intermittent) in the shift timing solenoid a intermittent circuit/system.
Apply the required relearn/adaptation procedure if specified by service information.
Road-test and verify P0789 remains cleared under the conditions that originally set the code.

Fix options

Retest after thermal/vibration simulation.
Wiggle-test harness during live monitoring.
Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$300-$1400

Common mistakes when diagnosing P0789

Replacing parts without verifying voltage, ground, and signal integrity first.
Ignoring related stored/pending codes that indicate upstream faults.
Skipping post-repair verification drive cycle and readiness checks.

P0789 in common vehicles

P0789 appears across makes such as Mazda, Subaru, Lexus, Jeep. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes P0789?

P0789 is commonly set by intermittent faults affecting shift timing solenoid a intermittent.

How much does it cost to fix P0789?

For P0789, repair costs are typically $300-$1400 depending on exact root cause, labor rates, and part quality.

Can I clear P0789 without repair?

You can clear P0789 temporarily, but the code usually returns until the underlying fault is corrected.