NOx Sensor Circuit Bank 2 Open (Generic)
The P4028 code means the vehicle's onboard diagnostic system has detected: NOx Sensor Circuit Bank 2 Open (Generic). This is a critical severity code.
- Keep driving?
- No -- stop driving
- DIY difficulty
- hard
- Estimated cost
- $300 - $800 (parts and labor)
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Common Symptoms
- Check Engine Light on
- SCR monitoring disabled for bank 2
- DEF system fault warning
- Speed derate possible
- Reduced engine power
Probable Causes (Ranked by Likelihood)
- Open circuit in bank 2 NOx sensor wiring Very High
- Failed bank 2 NOx sensor module High
- Connector damage at bank 2 sensor Moderate
- CAN bus communication failure with sensor Low
Step-by-Step Diagnostic Procedure
-
Check bank 2 NOx sensor connector and wiring
-
Verify CAN bus communication with NOx sensor
-
Test power supply to NOx sensor module
-
Swap sensors between banks to verify diagnosis
Frequently Asked Questions
Do all diesel trucks have two NOx sensors?
Most modern diesel trucks have at least two NOx sensors -- one before the SCR catalyst and one after. Some have separate sensors for each bank.
Can I drive with P4028?
No, the vehicle will likely enter reduced power mode or start a derate timer. The SCR system cannot function without NOx data.
Is P4028 a recall item?
Check with your dealer. Some manufacturers have issued extended warranties or service campaigns for NOx sensor failures.
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