OBD-II fault code

P099A: Shift Solenoid G Control Circuit Range/Performance

What it means

The control module detects a range or performance problem in the shift solenoid G control circuit.

At a glance

  • Usually lights the check-engine light
  • The engine or gearbox may go into limp mode

How it works

Shift solenoid G is an electrically operated valve that helps direct transmission fluid during gear changes. The control module monitors the solenoid G control circuit and sets this code when its electrical behavior or response falls outside the expected range or performance.

Common causes

Most likely first.

  1. Faulty shift solenoid G
  2. Open, shorted, or high-resistance wiring or connection
  3. Transmission control module fault

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

  1. Save freeze-frame data and review transmission live data for solenoid G commands and any shift or pressure changes linked to the fault.
  2. Inspect the solenoid G connector and accessible harness for loose terminals, corrosion, fluid contamination, chafing, or damaged insulation.
  3. Check transmission fluid level and condition using the vehicle's specified procedure, because fluid issues can contribute to poor shifting.
  4. Test the solenoid G circuit for opens, shorts, and excessive resistance using the wiring diagram and manufacturer's specifications.
  5. Test solenoid G's coil and operation per the manufacturer's procedure; check the transmission control module only if the solenoid and wiring pass.

Common fixes

  • Secure or repair a loose or corroded solenoid G connector.
  • Repair damaged or high-resistance wiring in the solenoid G circuit.
  • Correct transmission fluid level or condition if it is outside specification.
  • Replace shift solenoid G if testing confirms it does not meet specification.
  • Repair or replace the transmission control module if testing isolates the fault there.

Can I keep driving?

If the vehicle shifts harshly, slips, or enters limp mode, avoid unnecessary driving and towing; use a tow if gear control is unreliable. Continued slipping can overheat and damage the transmission.

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.

Codes for the same component