P2BAD Possible Causes
- Exhaust leaks
- Fuel contamination
- Faulty diesel particulate filter (DPF)
- Faulty NOx sensor
- Diesel exhaust fluid
- Faulty selective catalytic reduction (SCR) catalyst
How to Fix P2BAD Code
Check the “Possible Causes” listed above. Visually inspect the wiring harness and associated connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
Possible Symptoms
Check engine light illuminated (or service engine soon warning light)
P2BAD Meaning
The selective catalytic reduction system reduces nitrogen oxide (NOx) emissions by injecting a measured amount of diesel exhaust fluid or reductant into the exhaust gas stream entering the diesel particulate filter (DPF). In the selective catalytic reduction catalyst, the reductant reacts with NOx to form nitrogen, carbon dioxide, and water vapor. The upstream and downstream NOx sensors provide the engine control module (ECM) with engine-out and exhaust-out NOx levels.
The ECM uses the 2 NOx sensors to monitor exhaust NOx levels. The NOx sensor measures the amount of NOx and oxygen in the exhaust system. The first NOx sensor is located at the turbocharger outlet and monitors engine-out NOx emissions. The second NOx sensor is located in the DPF which monitors NOx levels exiting the DPF. The ECM varies the amount of reductant added by varying the reductant injector duty cycle in response to changes in engine-out exhaust NOx levels.