What it means
The fourth actuator supply rail is open. All loads on this rail are powerless and report follow-on faults.
At a glance
- Usually lights the check-engine light
How it works
Actuator supply rail D distributes electrical power to a group of controlled actuators, and the module monitors whether that supply is present. This code sets when the rail is open, so actuators on it may lose power and generate follow-on faults.
Common causes
Most likely first.
- Blown fuse on the supply rail
- Broken supply wire from main relay
Symptoms
- One or more actuator-related warning lights may come on
- Some engine or vehicle functions may be reduced or unavailable
- Check-engine light may be on
How to diagnose it
- Use a scan tool to record freeze-frame data and identify actuator-related codes that appeared with the rail D fault.
- Check battery condition and inspect the relevant fuse and main relay connections for obvious damage or looseness.
- Using the wiring diagram, identify the rail D fuse, relay, and powered actuators, then inspect the wiring and connectors for a break or corrosion.
- Check for supply at the rail D fuse and relay output using the manufacturer's procedure to locate where power is interrupted.
- If the supply path is intact, test the module's rail monitoring circuit and the relevant control output at the specified points.
Common fixes
- Replace a blown rail D fuse after checking for a short or overload that caused it to open.
- Repair a broken supply wire from the main relay to rail D.
- Clean or repair loose or corroded fuse, relay, or actuator terminals.
- Repair the supply control or monitoring circuit if testing confirms a module fault.
Can I keep driving?
Some engine or vehicle functions may be reduced or unavailable because actuators on rail D can lose power. Avoid driving if the engine runs poorly or a safety related function is affected.
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.