What it means
Regeneration control switch input reads stuck high — short to battery voltage. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The regeneration control switch sends a request for a parked diesel particulate filter regeneration. This code sets when the controller sees the switch input held high, commonly because the signal wire is shorted to battery voltage and the request state cannot be read reliably.
Common causes
Most likely first.
- Switch wire shorted to battery voltage
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Regeneration warning or request indicator may stay on
- Forced regeneration may not start when requested
How to diagnose it
- Use a scan tool to record freeze-frame data and observe the regeneration request input with the switch released and pressed.
- Check whether the request indicator remains on and whether the controller accepts an intentional request under the vehicle’s specified conditions.
- Inspect the switch harness and connectors for chafing, moisture, corrosion, pushed-back pins, or contact with a battery-voltage wire.
- Use the wiring diagram and manufacturer’s procedure to check the input wire for a short to battery voltage and verify switch operation.
- If the switch and wiring pass, test the controller connector and input circuit for unintended voltage or an internal fault.
Common fixes
- Repair the regeneration switch signal wire where it is contacting a battery-voltage source.
- Clean or replace damaged or corroded connector terminals in the switch circuit.
- Replace a faulty regeneration control switch if it holds the input high when disconnected from the harness.
- Repair the controller connector or input circuit if testing isolates the fault there.
Can I keep driving?
The controller may not accept a parked regeneration request, so follow aftertreatment warnings and do not ignore filter restriction alerts. Continued driving as soot loading rises can lead to reduced power or a required service regeneration.
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.