What it means
Regeneration control switch input reads stuck low — short to ground or stuck-closed contact. The ECM may see a constant regen request which it cannot service while the vehicle is moving.
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 reads the switch input continuously low, which may indicate a short to ground or a switch circuit stuck in the request state.
Common causes
Most likely first.
- Switch wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
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 save freeze-frame data and watch the regeneration request input with the switch released and pressed.
- Check whether the regeneration request indicator stays on and whether the controller recognizes a deliberate request under the specified conditions.
- Inspect the switch connector and harness for chafing, moisture, corrosion, loose terminals, or a signal wire touching ground.
- Following the wiring diagram and manufacturer’s procedure, test the input wire for a short to ground and check that the switch changes circuit state when operated.
- If the switch and harness test correctly, inspect and test the controller input connector for a grounded terminal or input fault.
Common fixes
- Repair the regeneration switch signal wire where it is shorted to ground.
- Clean or replace corroded or damaged terminals in the switch connector.
- Replace a faulty regeneration control switch if it holds the input low when disconnected from the harness.
- Repair the controller connector or input circuit if testing confirms the fault is there.
Can I keep driving?
A stuck request can prevent a proper parked regeneration, so follow the vehicle’s aftertreatment warnings and avoid ignoring rising soot or filter restriction alerts. Continued operation may 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.