What causes fault code P041B?

• Most likely: Soot or carbon buildup on the temperature sensor tip (insulating the sensor) • Likely: Faulty EGR temperature sensor B (NTC thermistor failure) • Possible: Damaged wiring harness or corrosion in the connector (high resistance) • Rare: Faulty or clogged EGR cooler (causing actual abnormal temperatures) • Rare: Improper ECU software calibration

Powertrain (Engine & Gearbox)Standard EOBD

P041B - Exhaust Gas Recirculation Temperature Sensor B Circuit Range/Performance

Q: What are the symptoms of fault code P041B?

• Check engine light illuminated • Vehicle may enter 'Limp home' mode (reduced power) • Increased fuel consumption • Rough idling or hesitation during acceleration • Failed emission test

Q: How do you fix fault code P041B?

STEP 1: Inspect the connector for sensor B for corrosion or loose pins. Clean if necessary. STEP 2: Remove the sensor and check for heavy soot accumulation. Clean gently with electronics cleaner. STEP 3: Perform a resistance test on the sensor (NTC type). Common values are between 10k-100k Ohms at 20°C (resistance should drop as heat increases). Verify 5V reference voltage from the ECU. STEP 4: Use a scan tool to monitor 'Live Data'. Compare EGR Temp A and B during warmup. If B lags or shows a static value despite cleaning, replace the sensor. STEP 5: If the fault persists after sensor replacement, check the EGR cooler for internal clogging or inefficiency.

Last updated:1 February 2026

Related:EGR Temperature Sensor B, EGR Cooler, EGR Valve, Engine Control Unit (ECU), Wiring Harness

System

Powertrain (Engine & Gearbox)

Related Fault Codes

P0400

Exhaust Gas Recirculation Flow Malfunction

P0401

Exhaust Gas Recirculation (EGR) Flow Insufficient Detected

P0402

Exhaust Gas Recirculation Flow Excessive Detected

P0403

Exhaust Gas Recirculation (EGR) Control Circuit

Technical Description

P041B is a generic OBD-II diagnostic trouble code (DTC) indicating that the Engine Control Unit (ECU) has detected an implausible signal in the EGR temperature sensor B circuit. This sensor is typically located after the EGR cooler to monitor cooling efficiency before exhaust gases are recirculated into the combustion chamber. If the temperature differential or signal voltage fluctuates outside of calibrated maps for specific load conditions, the ECU triggers the code. This fault impacts NOx emission strategies and may cause the system to enter a fail-safe mode, disabling EGR flow to protect internal engine components.

Possible Causes

Soot or carbon buildup on the temperature sensor tip (insulating the sensor)

Faulty EGR temperature sensor B (NTC thermistor failure)

Damaged wiring harness or corrosion in the connector (high resistance)

Faulty or clogged EGR cooler (causing actual abnormal temperatures)

Improper ECU software calibration

Symptoms

Check engine light illuminated

Vehicle may enter 'Limp home' mode (reduced power)

Increased fuel consumption

Rough idling or hesitation during acceleration

Failed emission test

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P041B - Exhaust Gas Recirculation Temperature Sensor B Circuit Range/Performance

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P041B - Exhaust Gas Recirculation Temperature Sensor B Circuit Range/Performance

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