P11B2 Possible Causes
- Faulty heated oxygen sensor (HO2S)
- Heated oxygen sensor (HO2S) harness is open or shorted
- Poor electrical connection in heated oxygen sensor (HO2S) circuit
How is code P11B2 repaired?
Start by checking the “possible causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.
Possible Symptoms
- Engine light on (or engine service warning light soon)
P11B2 Meaning
The reduction system uses two nitrogen oxide (NOx) sensors to monitor the amount of NOx in the engine exhaust gases. The first sensor is located at the turbocharger outlet and monitors the engine’s NOx level. The second NOx sensor is located between the selective catalytic reduction (SCR) and the diesel particulate filter (DPF) and monitors NOx levels downstream of the SCR. The second NOx sensor also provides the engine control module (ECM) with information about the exhaust oxygen level during DPF regeneration.
Each NOx sensor contains a sensing cell, a pump cell, and a heater. An exhaust gas sample passes through a diffusion gap between the sensing cell and the pump cell. The NOx sensor maintains a constant reference voltage across the sensing cell. An electronic circuit inside the sensor controls the pump current through the pump cell to maintain a constant voltage in the sensing cell. The amount of current required to maintain the reference voltage in the sensing cell is proportional to the NOx concentration in the exhaust.
The ECM varies the amount of diesel exhaust fluid (DEF) or reductant added by varying the duty cycle of the reductant injector in response to changes in engine exhaust NOx levels.
The smart NOx sensors consist of two components, the NOx module and the NOx sensor element, which are serviced as a unit. A circuit or performance condition with a NOx sensor is detected by the NOx sensor module. The smart NOx sensor module communicates the condition to the ECM via the serial data line. The ECM sets a DTC when a serial data message is received from the NOx sensor module.