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P codepowertrainMedium severity

P0546Exhaust Gas Temperature Sensor Circuit High (Bank 1, Sensor 1)

The exhaust gas temperature (EGT) sensor 1 circuit on Bank 1 is reading abnormally high voltage, usually meaning an open circuit or disconnected sensor.

Definition

The PCM monitors the signal voltage from the Bank 1, Sensor 1 exhaust gas temperature sensor, which is typically mounted upstream near the turbocharger, catalytic converter, or diesel particulate filter. Because most EGT sensors are negative-temperature-coefficient thermistors, an open circuit or broken sensor element pulls the signal to reference voltage, which the PCM interprets as an impossibly cold exhaust reading and sets P0546. The MIL illuminates, and on diesels the PCM may block DPF regeneration or reduce boost to protect components, causing soot loading and eventual limp mode. Gasoline turbo applications may limit boost or enrich fueling since the PCM can no longer verify exhaust temperatures.

Common causes

  • Failed EGT sensor with an open internal element (common from heat cycling)
  • Open or chafed signal wire between the sensor and PCM
  • Corroded, melted, or unplugged sensor connector near the exhaust
  • Poor sensor ground or open ground-side circuit
  • Damaged wiring from exhaust heat shielding contact
  • Rarely, a faulty PCM input circuit

Common misdiagnoses

  • Diesel particulate filter replaced when only the sensor circuit is open
  • Turbocharger replaced for a boost-limit/limp condition caused by the sensor
  • Catalytic converter replaced due to assumed overheating
  • EGR valve replaced for exhaust temperature complaints

Troubleshooting steps

  1. 1.Read live EGT data with a scan tool

    With the engine warm, Bank 1 Sensor 1 EGT should read a plausible value (roughly 150-600 C depending on load); a pegged reading of -40 C or maximum scale indicates an open circuit.

  2. 2.Inspect the sensor connector and harness

    Check the connector near the exhaust for melted plastic, green corrosion, or backed-out terminals, and look for wiring chafed against heat shields.

  3. 3.Measure sensor resistance

    Unplug the sensor and check resistance against the service specification at ambient temperature; an open (OL) reading confirms a failed sensor element.

  4. 4.Check circuit continuity to the PCM

    With the sensor unplugged, verify continuity of both signal and return wires to the PCM connector and confirm neither is shorted to voltage.

  5. 5.Verify the repair under load

    Clear the code, drive at highway load, and confirm the EGT PID tracks exhaust temperature smoothly and the code does not reset.

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