NOx Sensor Circuit High Input (Bank 1)
What does P2203 mean?
The P2203 code means the vehicle's onboard diagnostic system has detected: NOx Sensor Circuit High Input (Bank 1). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Emissions failure
- Reduced power or limp mode
- SCR warning indicator
- Abnormal exhaust readings
Probable Causes (Ranked by Likelihood)
- Short to voltage in NOx sensor wiring Very High
- Failed NOx sensor producing high signal High
- Water intrusion in the sensor connector Moderate
- Damaged wiring harness near exhaust heat Moderate
- ECM internal fault Low
Step-by-Step Diagnostic Procedure
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Read NOx sensor signal value -- should not be at maximum voltage constantly
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Inspect wiring harness for short to power or heat damage near exhaust components
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Check the sensor connector for water intrusion or pin damage
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Disconnect the sensor and check if the signal drops -- if so, sensor is at fault
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Replace the NOx sensor if wiring checks are normal
Frequently Asked Questions
What does high input mean for P2203?
High input means the NOx sensor is sending a voltage signal above the expected maximum to the ECM, usually indicating a short to voltage in the wiring or a failed sensor.
Can heat damage cause P2203?
Yes, the NOx sensor wiring runs near hot exhaust components and can melt or short if the harness protection is compromised.
Is P2203 common on diesel trucks?
Yes, NOx sensor codes are relatively common on diesel trucks with SCR aftertreatment systems, especially as the sensors age or if DEF quality is poor.