What it means
The gear shift control module A communication circuit reports a communication circuit condition. Shift command exchange is impaired.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Gear Shift Control Module A exchanges shift-related data with other controllers over a communication network. This code sets when the expected communication on Module A's circuit is faulty, without specifying a low or high circuit condition.
Common causes
Most likely first.
- Communication lost
- Wiring fault
- Gateway module routing CAN messages incorrectly
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
- Scan all modules and save freeze-frame data, noting which controllers report lost communication with Module A.
- Check whether Module A responds to the scan tool and review network status for missing or intermittent messages.
- Inspect Module A connectors and the accessible network wiring for loose pins, corrosion, chafing, or water intrusion.
- Check Module A's power and ground connections, since a supply fault can interrupt communication.
- If wiring and supplies are sound, test the network circuit and gateway message routing according to the manufacturer's procedure.
Common fixes
- Reconnect or clean a loose or corroded Module A connector.
- Repair damaged network wiring or a poor Module A power or ground connection.
- Correct gateway routing or configuration if testing identifies a message-routing problem.
- Repair or replace Module A if it fails communication testing despite verified network and power connections.
Can I keep driving?
With harsh or missing shifts or limp mode, limit driving to reaching a safe location and avoid high-speed or heavy-traffic journeys; loss of module communication can make shifting unreliable. Stop if the vehicle loses drive or shifts unpredictably.
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.