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P0548 – Exhaust Gas Temperature Sensor Circuit Low - Bank 2 Sensor 1 (OBD2)

P0548 means "Exhaust Gas Temperature Sensor Circuit Low - Bank 2 Sensor 1". The voltage the control unit measures in the exhaust gas temperature (EGT) sensor circuit is below the permitted minimum. For a sensor this usually means the signal wire is shorted to ground or the reference voltage is missing; for an actuator, that its control wire is shorted to ground.

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P0548 quick summary

Fault codeP0548
MeaningExhaust Gas Temperature Sensor Circuit Low - Bank 2 Sensor 1
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityMedium
Can I drive?Yes, gently. On diesels DPF regeneration may stop, so have it fixed before the filter clogs.
Repair cost€40 – €300

How exhaust gas temperature sensors work

Exhaust gas temperature sensors measure the exhaust temperature at several points to protect the turbocharger and catalytic converter and to control DPF regeneration.

EGT sensors are thermistor or thermocouple-type sensors screwed into the exhaust – typically before the turbocharger, before the oxidation catalyst and before or after the DPF on diesels. They measure temperatures from below zero up to around 900–1,000 °C.

The control unit uses the readings to protect components from overheating (it reduces power when temperatures get too high) and to control DPF regeneration, which needs exhaust temperatures around 600 °C. Codes P0544–P0549 report circuit faults for sensor 1 of bank 1 and bank 2.

Sensors fail from heat cycling, their cables are damaged by heat and vibration, and connectors corrode. A faulty EGT sensor on a diesel often stops DPF regeneration, which can lead to DPF blockage codes.

Bank 2 is the cylinder row that does NOT contain cylinder 1, so this code only appears on V6, V8, V10, V12 and boxer engines.

Symptoms of P0548

  • Check Engine light on
  • DPF regeneration not completing, DPF warning
  • Reduced power or limp mode
  • Implausible temperature readings in live data
  • Often no driving symptoms

Most common causes of P0548 (most likely first)

Mechanic's Pro Tip

EGT sensors are often seized in the exhaust. Apply penetrating oil and loosen them with the exhaust warm (not hot) – a snapped sensor thread turns a cheap job into an expensive one.

  1. 1.Signal or control wire shorted to ground

    Most likely

    Look for chafed insulation where the harness touches the engine, exhaust brackets or body edges.

  2. 2.Missing 5 V reference or supply voltage

    An open reference wire or a shorted sensor elsewhere on the same reference circuit can pull it down.

  3. 3.Internal short in the exhaust gas temperature (EGT) sensor

  4. 4.Failed EGT sensor

    Heat cycling breaks the sensing element.

  5. 5.Damaged sensor cable

    Melted or broken near hot exhaust parts.

  6. 6.Corroded connector

  7. 7.Wiring fault to the control unit

Step-by-step diagnostic guide

  1. 1

    Read codes and compare temperatures

    Read all codes. On a cold engine all EGT sensors should show roughly the outside temperature.

  2. 2

    Measure the signal voltage

    With the ignition on and the exhaust gas temperature (EGT) sensor plugged in, back-probe the signal wire. Then unplug it and check the reference/supply and ground wires separately.

    Multimeter: Signal near 0 V = short to ground or no reference. Reference wire: about 5 V with ignition on. Signal wire to ground with connector unplugged: no continuity.

  3. 3

    Check the cable and connector

    Inspect the sensor cable along its length for heat damage and the connector for corrosion.

  4. 4

    Measure the sensor

    Measure the resistance and compare with the specification.

    Multimeter: Many PTC/NTC EGT sensors read roughly 200–250 Ω at room temperature (PT200 type); check the type for your sensor.

  5. 5

    Check wiring

    Check the wiring to the control unit for opens and shorts.

  6. 6

    Replace and verify

    Replace the sensor using anti-seize on the thread, clear codes and check that DPF regeneration completes.

Frequently asked questions

Can I keep driving with P0548?

Yes, gently. On diesels DPF regeneration may stop, so have it fixed before the filter clogs.

How much does it cost to fix P0548?

Typical repair costs are 40 € – 300 €, depending on the cause and the vehicle. The most common fixes are: signal or control wire shorted to ground; missing 5 V reference or supply voltage; internal short in the exhaust gas temperature (EGT) sensor. Always confirm the cause with the tests above before buying parts.

Can a bad EGT sensor block the DPF?

Indirectly yes. Without a reliable temperature signal the control unit may not start or finish regenerations, so soot builds up.

How many EGT sensors does a car have?

Petrol engines may have one or none; modern diesels often have two to four.

What is the difference between P0548 and similar codes?

P0548 belongs to a group of codes for the same component that differ in the type or location of the fault: P0544 – Exhaust Gas Temperature Sensor Circuit - Bank 1 Sensor 1; P0545 – Exhaust Gas Temperature Sensor Circuit Low - Bank 1 Sensor 1; P0546 – Exhaust Gas Temperature Sensor Circuit High - Bank 1 Sensor 1; P0547 – Exhaust Gas Temperature Sensor Circuit - Bank 2 Sensor 1; P0549 – Exhaust Gas Temperature Sensor Circuit High - Bank 2 Sensor 1. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.