P4003 moderate

Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 1 Intermittent (Generic)

The P4003 code means the vehicle's onboard diagnostic system has detected: Exhaust Gas Temperature Sensor Circuit Bank 1 Sensor 1 Intermittent (Generic). This is a moderate severity code.

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Keep driving?: Short distances only
DIY difficulty: hard
Estimated cost: $80 - $400 (parts and labor)

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Common Symptoms

Check Engine Light on intermittently
Sporadic DPF regeneration issues
Erratic exhaust temperature readings
Occasional reduced power mode

Probable Causes (Ranked by Likelihood)

Loose or corroded EGT sensor connector Very High
Intermittent break in sensor wiring High
EGT sensor failing under heat cycles Moderate
Vibration causing wiring contact issues Low

Step-by-Step Diagnostic Procedure

Wiggle test EGT sensor connector and wiring while monitoring live data
Inspect connector pins for corrosion or looseness
Check wiring harness routing for chafe points near exhaust
Monitor sensor reading over multiple drive cycles for dropouts

Frequently Asked Questions

Why does this code come and go?

Intermittent codes are usually caused by loose connections or damaged wiring that makes and breaks contact due to heat expansion, vibration, or moisture.

Is an intermittent EGT code serious?

It should be addressed because the DPF system relies on accurate temperature data. If ignored, the DPF may not regenerate properly.

How do I find an intermittent wiring fault?

Perform a wiggle test on the connector and wiring while watching live sensor data. Also inspect the harness for chafing where it passes near exhaust components.