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DTC codes / P05xx · Vehicle speed, idle control and auxiliary inputs / P0545

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

P0545 means the engine computer has detected an abnormally low voltage signal from the exhaust gas temperature (EGT) sensor located before the catalytic converter on bank 1, which is the side of the engine that contains cylinder number one. The sensor's internal thermistor normally varies resistance with temperature, and a low signal tells the computer the exhaust is colder than it should be or that the circuit is shorted to ground.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Reduced engine power or limp mode if the computer cannot trust exhaust temperature data for protection strategies
  • Poor fuel economy or altered regeneration behavior on diesel vehicles equipped with a particulate filter
  • Intermittent stumble or rough running if the sensor wiring is chafed and shorting
  • A stored freeze-frame showing low sensor voltage at the moment the fault set

Common causes, most likely first

  1. A short to ground in the sensor signal wire, often where the harness rubs against a heat shield or bracket
  2. A failed EGT sensor whose internal thermistor has drifted or shorted
  3. Corroded, loose, or pushed-back pins at the sensor connector or the engine computer connector
  4. Water intrusion into the connector causing a low-resistance path to ground
  5. A faulty engine computer driver circuit, though this is rare compared with wiring faults
  6. Exhaust leaks upstream of the sensor that let cooler air reach the tip and skew the reading

How to diagnose and fix it

  1. Connect a scan tool and read the EGT sensor voltage live to confirm the signal is pinned low rather than intermittent
  2. Inspect the sensor harness from the connector to the computer for chafing, melted insulation, or contact with hot exhaust parts
  3. Disconnect the sensor and measure resistance across its terminals, comparing the reading to the temperature-based specification for the vehicle
  4. Check for continuity between the signal wire and ground with the sensor unplugged to rule out a short in the harness
  5. Clean and re-seat the connector, then clear the code and verify the voltage responds correctly when the engine warms up
  6. Replace the EGT sensor if resistance testing proves it is out of range, using the correct thread sealant and torque
  7. If the harness and sensor test good, perform a wiggle test and check the computer connector before condemning the computer

Why a low EGT signal is not always the sensor

  • A shorted signal wire is far more common than a failed sensor on high-mileage vehicles, so always ohm the harness before buying parts.
  • On diesel engines, a low EGT reading can prevent or alter diesel particulate filter regeneration, so ignoring the code can lead to a plugged filter.
  • The sensor may test fine at room temperature but fail only when hot, so resistance checks should be repeated after a road test.
  • Exhaust leaks upstream of the sensor pull in cool air and can mimic a low signal, so inspect gaskets and welds before replacing the sensor.
  • Some vehicles set P0545 when the connector is simply unplugged, so check that the latch is fully seated before deeper diagnosis.

Can I keep driving with P0545?

You can usually drive short distances to a repair shop, but avoid heavy towing or sustained high-load driving because the computer may be limiting power or regeneration. If the engine enters limp mode or you notice a strong exhaust smell, stop driving and have it inspected.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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