How many EGT sensors does my diesel have?

Most modern diesels have 2–4 EGT sensors at different points in the exhaust — typically before the turbo, before the DPF, and after the DPF.

Can I drive with P0545?

Yes, but DPF regeneration will be disrupted. Left long-term, a blocked DPF will result, which is an expensive repair.

How much does an EGT sensor cost?

EGT sensors typically cost £25–£80 for the part. Labour varies — some are easy to access, others require significant exhaust disassembly.

Will P0545 cause my DPF to block?

Yes, eventually. The ECU uses EGT sensor data to manage regeneration temperature. Without accurate readings, it cannot safely perform DPF regeneration.

Why does EGT sensor wiring keep failing?

The wiring runs very close to the exhaust and is subject to extreme heat cycles. Over time, the insulation cracks and conductors break. Using correct high-temperature wire and sleeving for repairs is essential.

What temperature does an EGT sensor measure?

Exhaust gas temperatures can range from 100°C at idle to over 900°C during DPF regeneration. EGT sensors are designed to withstand these extremes, but the wiring is often the weak point.

P0545 — Fault Code | Mr Auto Fixer

What Is P0545?

P0545 is stored when the ECU detects a lower than expected voltage from exhaust gas temperature (EGT) sensor 1. EGT sensors are used primarily on diesel engines to monitor the temperature of exhaust gases at various points in the exhaust system — typically before and after the DPF.

These sensors are critical for DPF regeneration management. If the ECU cannot trust the EGT sensor reading, it may prevent active regeneration from occurring, leading to DPF blockage over time. A circuit low fault usually points to a short to earth in the wiring or a failed sensor.

Common Symptoms

Engine management light on
DPF regeneration not completing
DPF warning light
Reduced engine performance
Increased fuel consumption
Possible limp mode on some vehicles

Common Causes

Short to earth on the EGT sensor signal wire

Failed EGT sensor with internally shorted element

Damaged sensor wiring — heat damage near the exhaust is very common

Corroded or damaged connector at the sensor

Open circuit in sensor earth return wire (causes low voltage reading on some systems)

ECU reference voltage supply fault

How to Diagnose P0545

Inspect the Sensor Wiring

EGT sensors are mounted directly on the exhaust and their wiring is subject to extreme heat. Inspect the wiring carefully for melted insulation, broken wires, or chafing near the exhaust pipe. This is the most common cause of P0545.

Check Sensor Connector

Disconnect the EGT sensor connector and inspect for corrosion or damaged pins. Clean with contact cleaner and reseat. Clear the code and retest.

Measure Sensor Resistance

EGT sensors are thermocouples or NTC thermistors. With the engine cold, measure resistance at the sensor terminals. Compare to manufacturer specification. Out-of-range resistance indicates a failed sensor.

Check Reference Voltage

With ignition on and connector plugged in, back-probe the signal wire. No reference voltage from the ECU side indicates a wiring fault between ECU and sensor.

Replace the Sensor

If wiring is intact and the sensor tests faulty, replace it. EGT sensors on high-mileage diesels frequently fail due to heat cycling fatigue. Use an OEM or quality aftermarket replacement.

Verify DPF Operation

After replacing the sensor and clearing the code, run a long motorway drive to trigger a DPF regeneration cycle and confirm the system is operating correctly.

Heat DamageEGT sensor wiring runs extremely close to the exhaust. When replacing the sensor, always inspect at least 30cm of wiring away from the sensor. Heat-damaged sections need proper repair with high-temperature wire and sleeving — not standard auto-electrical wire.

Verdict

Inspect all wiring near the exhaust first — heat damage is the leading cause of P0545. If wiring is intact, test and replace the sensor.

P0545 — Fault Code