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P codepowertrainMedium severity

P0545Exhaust Gas Temperature Sensor Circuit Low (Bank 1, Sensor 1)

The first exhaust gas temperature sensor on bank 1 is reading a lower circuit voltage than possible, usually from a short to ground.

Definition

The ECM feeds EGT sensor 1 (bank 1) through a reference circuit and sets P0545 when the signal voltage drops below the plausible minimum — the classic signature of a sensor or harness shorted to ground, which typically pegs the reported temperature at one extreme. Because the ECM can no longer trust exhaust temperature on the protective side of the turbo and aftertreatment, it illuminates the MIL, generally blocks active DPF regeneration on diesels, and may reduce power as a safeguard. Left unresolved, soot accumulates in the DPF until the vehicle forces a derate or requires filter service.

Common causes

  • EGT sensor shorted internally after thermal cycling
  • Sensor harness melted against the exhaust and shorted to ground
  • Chafed wiring where the pigtail passes brackets or heat shields
  • Moisture intrusion shorting the connector
  • Signal and return wires shorted together
  • ECM input fault (rare)

Common misdiagnoses

  • DPF replaced for soot loading that the inhibited regens caused
  • A different EGT sensor replaced due to position-numbering confusion
  • Turbocharger
  • Exhaust back-pressure sensor

Troubleshooting steps

  1. 1.Confirm the pegged reading

    Check the bank 1 sensor 1 EGT PID cold; a reading stuck at an extreme while other EGT sensors read ambient confirms a circuit fault, not a real temperature.

  2. 2.Unplug the sensor and watch the PID

    If the reading swings to the opposite extreme with the connector open, the harness and ECM are intact and the sensor is shorted.

  3. 3.Hunt the harness short if it stays pegged

    With the sensor and ECM disconnected, ohm the signal wire to chassis ground; continuity confirms melted or chafed wiring to locate along the exhaust routing.

  4. 4.Inspect for heat damage

    Look specifically where the pigtail nears the manifold, turbo, or downpipe for glazed, brittle insulation and repair with high-temperature sleeving.

  5. 5.Replace the sensor and verify

    Fit a new EGT sensor torqued to spec, clear codes, and confirm the PID reads ambient cold and climbs normally on a test drive so regeneration is re-enabled.

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