P21B4

Symptoms

• Check Engine light comes on
• Reduced engine power
• Increased fuel consumption
• Unusual odors from the exhaust system
• Engine transition to emergency mode

Causes

• NOx canister temperature sensor malfunction
• Problems with the adsorber regeneration system
• Clogged or damaged NOx adsorber
• Malfunctions in the engine management system
• Problems with the wiring harness to the temperature sensor

How to Fix

1. Check the readings of the NOx adsorber temperature sensor
2. Inspect the NOx adsorber for damage
3. Check the temperature sensor circuit for opens and shorts
4. Conduct diagnostics of the adsorber regeneration system
5. If necessary, replace the NOx adsorber or temperature sensor

Related codes

Error P21B4 by Vehicle Brand