P208E: Reductant Injection Valve Stuck Closed (Bank 1 Unit 1)

What it means

The DEF injection valve at bank 1 unit 1 does not open when commanded — typically crystallised DEF blocks the nozzle, no flow into the SCR.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

The reductant injection valve at bank 1 unit 1 meters DEF into the exhaust for SCR NOx reduction. The module monitors the valve's response to an opening command and sets this code when the valve remains closed and DEF flow is not detected as expected.

Common causes

Most likely first.

1. Nozzle crystallised
2. Valve seized
3. Carbon or debris buildup preventing free movement

Symptoms

• Check engine light or NOx warning on
• AdBlue/DEF level or quality warning
• Possible no-start countdown after ignore period
• Failed emissions inspection (NOx)

How to diagnose it

1. Check freeze-frame data and SCR or DEF warnings to see when the bank 1 unit 1 valve failed to respond.
2. Inspect the bank 1 unit 1 injector nozzle and surrounding exhaust area for crystallised DEF or deposits.
3. Check the valve connector and wiring for damage or poor connections that could prevent it opening.
4. Use the manufacturer's procedure to command the valve and verify whether it actuates and delivers DEF.
5. If electrical operation is present but flow remains absent, inspect the valve for seizure or blockage using the manufacturer's service procedure.

Common fixes

• Clean crystallised DEF from the bank 1 unit 1 nozzle using the manufacturer's service guidance.
• Repair a damaged connector or wiring fault preventing the valve from opening.
• Replace the bank 1 unit 1 reductant injection valve if it is seized or remains blocked.
• Clear related SCR faults and verify DEF dosing after the repair.

Can I keep driving?

Avoid continued driving if the vehicle has entered reduced-power mode, and do not ignore a DEF no-start countdown. A closed injector prevents proper NOx control and can lead to emissions-system restrictions.