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DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P20E4

P20E4Exhaust Gas Temperature Sensor 2/3 Correlation (Bank 1)

P20E4 indicates that the powertrain control module (PCM) has detected an implausible correlation between the exhaust gas temperature (EGT) sensor 2 and sensor 3 on bank 1. The PCM compares the two sensor readings under specific operating conditions and sets this code when the temperature values deviate beyond the calibrated threshold, suggesting a sensor, wiring, or exhaust system fault.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

  • Malfunction indicator lamp (MIL) illuminated, often with no other noticeable symptoms
  • Reduced engine power or limp mode in some vehicles
  • Poor fuel economy or altered regeneration behavior on diesel engines
  • Intermittent rough running or hesitation under load
  • Possible black smoke or excessive exhaust odor from incomplete regeneration
  • No drivability issues at all in many cases

Common causes, most likely first

  1. Faulty EGT sensor 2 or sensor 3 (internal short, open circuit, or degraded response)
  2. Damaged or corroded wiring harness or connector at either sensor
  3. Exhaust leaks upstream of the sensors causing false temperature readings
  4. Restricted exhaust or partially clogged diesel particulate filter (DPF) altering temperature gradients
  5. PCM software calibration issue or outdated firmware
  6. Failed sensor mounting or loose sensor in the exhaust bung
  7. Corrosion or water intrusion in the sensor connector causing signal interference

How to diagnose and fix it

  1. Perform a visual inspection of both EGT sensors and their wiring for damage, corrosion, or loose connections
  2. Use a scan tool to read live EGT sensor 2 and sensor 3 values during a test drive and compare them for plausibility
  3. Check for exhaust leaks upstream of the sensors using a smoke machine or visual inspection of gaskets and pipes
  4. Measure sensor resistance and compare to manufacturer specifications if available
  5. Verify sensor part numbers and installation depth match the application
  6. Check for technical service bulletins (TSBs) or PCM software updates related to EGT correlation
  7. Replace the faulty sensor or repair wiring as needed, then clear codes and verify the repair with a road test

What most technicians overlook on P20E4

  • A correlation code does not automatically mean both sensors are bad; often only one sensor is skewed, and replacing both without testing wastes money.
  • Exhaust leaks between the two sensors can create a temperature difference that mimics a sensor fault, so always inspect the exhaust system before condemning sensors.
  • On diesel vehicles, a failing DPF regeneration can cause abnormal temperature spreads that set this code even when sensors are healthy.
  • Sensor connectors often suffer from water intrusion or corrosion that causes intermittent correlation faults, especially in areas with road salt.
  • After replacing a sensor, some vehicles require a relearn or adaptation reset to prevent the code from returning immediately.

Can I keep driving with P20E4?

The vehicle is generally safe to drive with this code, but avoid heavy loads or sustained high-speed driving until diagnosed, as incorrect EGT readings can affect regeneration and emissions performance. If the engine enters limp mode, seek service promptly.

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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