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DTC codes / P04xx · Auxiliary emission controls / P041C

P041CEGR Temperature Sensor B Circuit Low

P041C means the powertrain control module (PCM) has detected a low-voltage signal from the exhaust gas recirculation (EGR) temperature sensor B circuit, which typically monitors the temperature of the EGR flow or the EGR cooler on the cooler side. The PCM expects the sensor's return voltage to stay within a calibrated range, and a sustained low reading indicates a short to ground, an open circuit, or a sensor that has failed in a low-resistance state.

SystemPowertrain
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Rough idle or slight hesitation when the EGR valve opens, especially when the engine is cold
  • Reduced fuel economy as the PCM may disable EGR operation and default to a richer mixture
  • Intermittent stumble or surge during light-throttle cruising if the sensor signal is erratic
  • Failed emissions test due to the EGR monitor not completing or reporting a fault
  • In rare cases, a noticeable decrease in power if the PCM limits EGR flow to protect the engine

Common causes, most likely first

  1. EGR temperature sensor B internally shorted, pulling the signal voltage toward ground
  2. Damaged or chafed sensor wiring shorted to ground between the sensor and the PCM
  3. Corroded, loose, or disconnected electrical connector at the sensor
  4. Open circuit in the sensor ground or reference voltage circuit causing a false low reading
  5. Failed PCM driver or internal pull-up resistor on the sensor signal circuit (less common)
  6. Exhaust leaks or coolant contamination affecting the sensor's thermal response (indirect cause)

How to diagnose and fix it

  1. Connect a scan tool and record the freeze-frame data and sensor B voltage with the key on and engine running to confirm the low signal
  2. Visually inspect the sensor, connector, and wiring harness for chafing, corrosion, or loose pins, and repair as needed
  3. Measure resistance and voltage at the sensor connector and compare with manufacturer specifications to isolate the sensor from the circuit
  4. Check the sensor ground circuit for excessive resistance and the reference voltage for correct value with a digital multimeter
  5. If the circuit tests good, replace the EGR temperature sensor B with a quality part and clear the code
  6. Clear codes and perform a road test to verify the EGR monitor completes and the code does not return
  7. If the code persists after sensor replacement, diagnose the PCM signal circuit for a short to ground or an internal PCM fault

What a low EGR temp signal really means

  • A low signal does not always mean the sensor is bad; a short to ground anywhere in the harness will produce the same code, so always check the wiring before replacing parts.
  • On many vehicles the EGR temperature sensor B is a thermistor whose resistance drops as temperature rises, so a low voltage reading can also be caused by an open ground circuit rather than a shorted sensor.
  • Technicians often overlook that a stuck-open EGR valve can cause the sensor to see abnormally low temperatures, setting this code even though the sensor itself is fine.
  • After replacing the sensor, the PCM may need to relearn the EGR temperature range, so clearing codes and completing a drive cycle is essential to avoid a false repeat.
  • This code can be set by a poor engine ground or a weak battery that causes the PCM to misread sensor voltage during cranking, so check the charging system first.

Can I keep driving with P041C?

The vehicle is generally safe to drive with P041C because the PCM will default to a conservative EGR strategy, but avoid long trips or heavy loads until the fault is repaired to prevent increased emissions and potential fuel economy loss.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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