What Does P2203 Mean?
The NOx sensor circuit on Bank 1 is reading voltage or signal values that are too high compared to expected parameters. This indicates either a sensor fault, wiring issue, or a condition causing abnormally high NOx readings.
Common Causes
35%
Failed NOx sensor with internal fault on Bank 1
25%
Open circuit or high resistance in NOx sensor wiring harness
20%
Poor ground connection causing high signal voltage
12%
SCR system malfunction causing genuinely high NOx levels
8%
PCM internal fault on NOx sensor input circuit
Diagnostic Steps
1
Step 1: Inspect NOx sensor connector and wiring for damage, corrosion, or loose connections
2
Step 2: Using multimeter, check for open circuits or high resistance in signal and ground wires
3
Step 3: Verify proper ground connection at sensor and PCM; clean and secure as needed
4
Step 4: Monitor live NOx sensor values during various operating conditions to determine if readings are genuinely high or sensor is faulty
5
Step 5: Replace NOx sensor if wiring and grounds test normal; if readings remain high with new sensor, diagnose SCR system for DEF delivery or catalyst issues
Estimated Repair Cost
$250 - $1,500
Parts + labor, varies by vehicle and location
The NOx sensor circuit on Bank 1 is reading voltage or signal values that are too high compared to expected parameters. This indicates either a sensor fault, wiring issue, or a condition causing abnormally high NOx readings.
The most common cause of P2203 (NOx Sensor Circuit High Bank 1) is: Failed NOx sensor with internal fault on Bank 1
Typical repair costs for P2203 range from $250 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive but emissions will increase significantly. Diesel vehicles will likely enter derate mode limiting performance if not repaired within manufacturer-specified timeframe.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2203 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control / SCR System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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