What it means
The control line for the aftertreatment glow plug (used on some diesels to ignite injected HC during DPF regeneration) is open. Active regeneration cannot start.
At a glance
- Usually lights the check-engine light
How it works
On diesels equipped with this system, an aftertreatment glow plug heats the exhaust so injected hydrocarbons can ignite during DPF regeneration. The module monitors the glow plug relay control circuit and sets P269B when it detects an open control path, so it cannot command the heater reliably.
Common causes
Most likely first.
- Open coil in glow plug control relay
- Broken control wire
Symptoms
- Check-engine light
- DPF warning light
- More frequent or unsuccessful DPF regeneration
How to diagnose it
- Read freeze-frame data and regeneration status to see when the open-circuit fault occurred and whether regeneration was being requested.
- Inspect the aftertreatment glow plug relay and its control-wire connectors for loose plugs, damaged insulation, corrosion, or pulled-back pins.
- With the circuit commanded, check for the expected control signal at the relay using the vehicle wiring diagram and manufacturer's specification.
- Check continuity through the relay coil and control wire with power isolated as specified by the manufacturer to locate the open section.
- If the wiring and relay test correctly, verify the module's control output and grounds using the manufacturer's diagnostic procedure.
Common fixes
- Reconnect a loose relay or control-wire connector and secure the harness.
- Repair a broken control wire or damaged terminal.
- Replace the relay if its control coil is open.
- Repair the module circuit only if testing confirms its output is faulty.
Can I keep driving?
You can usually drive gently if the engine runs normally, but avoid repeated short trips that prevent regeneration and respond promptly to a DPF warning. Failed regeneration can allow soot loading to rise and may eventually restrict the exhaust.
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.