U029D GMC Code - Lost Communication With NOX Sensor 'A'
|U029D GMC code possible causes
- Faulty Nitrogen Oxide (NOx) Sensor Bank 'A'
- Nitrogen Oxide (NOx) Sensor Bank 'A' harness is open or shorted
- Nitrogen Oxide (NOx) Sensor Bank 'A' circuit poor electrical connection
|How do I fix the U029D GMC code?Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
|Cost of diagnosing the U029D GMC code
Labor: 1.0The cost of diagnosing the U029D GMC code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
|What are U029D GMC code possible symptoms?
- Engine Light ON (or Service Engine Soon Warning Light)
|U029D GMC code descriptionThe reductant system uses two Nitrogen Oxide (NOx) sensors to monitor the amount of NOx in the engine's exhaust gas. The first sensor is located at the outlet of the turbocharger and monitors the engine out 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 on the exhaust oxygen level during DPF regeneration.
Each NOx sensor contains a sensing cell, a pumping cell, and a heater. A sample of exhaust gas passes through a diffusion gap between the sensing cell and the pumping cell. The NOx sensor maintains a constant reference voltage across the sensing cell. An electronic circuit within sensor controls the pump current through the pumping cell in order 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 concentration of NOx in the exhaust.
The ECM varies the amount of Diesel Exhaust Fluid (DEF) or reductant added by varying the reductant injector duty cycle in response to changes in engine exhaust out NOx levels. The smart NOx sensors consist of two components, the NOx module and the NOx sensor element that 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 over the serial data line. The ECM sets a DTC when a serial data message is received from the NOx sensor module.
|Need more information with the U029D GMC code?Need more information on how to fix the U029D GMC code? Get Access to Factory Service Manuals
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