Emissions

P247B — Exhaust Gas Temperature Sensor Performance (Bank 1, Sensor 3)

Severity: medium Drive with care, to a shop

What P247B means

The ECU compares the signal from the third exhaust gas temperature sensor on bank 1, usually located after the diesel particulate filter, with a calculated model and neighboring sensors. The code sets when the signal is off, stuck or too slow to respond. The ECU uses this data to manage filter regeneration and emissions control.

Symptoms

  • Check Engine light on
  • Particulate filter regeneration monitoring faults
  • Related SCR efficiency codes
  • Frequent or failed regeneration attempts
  • Possible reduced power (limp mode)
  • Higher fuel use during regenerations

Possible causes

  1. Failed post-filter exhaust temperature sensor
  2. Sensor tip covered in soot, distorting readings
  3. Wiring damage, open circuit, or short to ground or power
  4. Corroded or damaged sensor connector
  5. Exhaust leak near the sensor
  6. ECU fault (rare)

How to diagnose

  1. Scan all codes and freeze frame data, noting other EGT or filter pressure codes
  2. Inspect the sensor, connector and harness for chafing, heat damage and corrosion
  3. Check for exhaust leaks near the sensor
  4. Compare sensor 3 with the other EGT sensors on a cold engine; they should read close together
  5. Warm the engine and confirm the reading rises smoothly and tracks the other sensors
  6. Test sensor resistance and check reference, signal and ground per the wiring diagram
  7. Assess the particulate filter and SCR system if related codes are present

Common fixes

  • Replace the exhaust gas temperature sensor
  • Repair the wiring or connector
  • Fix the exhaust leak
  • Run a forced regeneration, or clean or replace the particulate filter if damaged
  • Clear the code and verify it does not return

Questions and answers

What does P247B mean?

The ECU considers the signal from the third exhaust gas temperature sensor on bank 1 implausible. This is most often the sensor after the particulate filter.

Can I drive with P247B?

For a short time, yes, but get it diagnosed soon. Without a reliable reading, regeneration and filter protection may not work properly.

How do I fix P247B?

Check the wiring, connector and exhaust leaks first, then test the sensor. Replacing the sensor or repairing the harness usually solves it.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.