P0545
Exhaust Gas Temperature Sensor Circuit Low (Bank 1 Sensor 1)P0545 is a generic OBD-II powertrain diagnostic trouble code: Exhaust Gas Temperature Sensor Circuit Low (Bank 1 Sensor 1). It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0545 means
P0545 is set when the ECM detects that the signal voltage from the Bank 1 Sensor 1 Exhaust Gas Temperature sensor has fallen below the lower limit of the expected operating range for a sustained period. The EGT sensor is a negative temperature coefficient (NTC) thermistor — resistance decreases as temperature rises, so signal voltage also falls with increasing temperature. A voltage that stays abnormally low therefore indicates either an implausibly high temperature reading, or more commonly, a wiring short to ground that is pulling the signal line below the ECM's minimum acceptance threshold.
On diesel vehicles with DPF systems, a low-circuit fault causes the ECM to lose confidence in the measured exhaust temperature and may force it to assume worst-case high temperatures, suppressing active regeneration and applying conservative fuel and boost limits. The sensor wiring harness runs in close proximity to hot exhaust components; prolonged heat exposure causes insulation breakdown and eventual short-to-ground faults. Connector pin corrosion from condensation pooling in the underbody harness is another frequent cause, particularly on older high-mileage vehicles.
Diagnosis should distinguish between a true short-to-ground (signal wire resistance to chassis ground below ~1 kΩ with connector unplugged) and a failed sensor whose resistance at operating temperature has dropped out of range. Unplugging the sensor and checking whether the fault code changes to P0546 (high circuit) quickly confirms whether the fault is in the sensor or in the wiring to the ECM.
Common causes
Most-frequently reported root causes when P0545 is logged.
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1
Wiring short to earth/ground on the EGT sensor signal wire
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2
Failed EGT sensor with internally shorted thermistor element
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3
Damaged sensor connector with pin-to-pin short from moisture or debris
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4
Chafed wiring harness contacting exhaust pipe or chassis metalwork
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5
ECM signal input circuit fault (internal short — rare)
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6
Incorrect replacement sensor with wrong resistance curve
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7
Sensor connector partially unseated causing intermittent low-voltage signal
Symptoms drivers notice
How to diagnose P0545
A typical diagnostic flow when this code is present.
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1
Unplug the EGT sensor connector and check whether the stored code changes to P0546 on the next key cycle — if it does, the fault is in the sensor or its local connector, not the ECM-side wiring
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2
With the connector unplugged, measure resistance between the signal pin and chassis ground; a reading below ~1 kΩ confirms a wiring short to ground
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3
Inspect the sensor harness from the sensor bung back to the bulkhead for heat damage, chafing against exhaust or chassis, and corroded connector pins
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4
Measure EGT sensor resistance at a known temperature and compare against the resistance-temperature specification; replace sensor if out of range
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5
Check for exhaust leaks at the sensor bung that could cause localised overheating of the wiring immediately adjacent to the sensor
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6
Clear DTC, run a drive cycle, and monitor live EGT data to confirm repair — voltage should rise smoothly from ambient reference to operating range (typically 1.5–4.0 V at idle)
Vehicles where we've handled P0545
Platforms in our catalogue with confirmed P0545 coverage.
Related powertrain codes
Frequently asked questions
Why does unplugging the sensor help diagnose P0545?
When the sensor is disconnected, the ECM sees an open circuit on the signal line, which drives the input to maximum voltage. If the code then changes to P0546 (high circuit), the short-to-ground fault is isolated to the sensor or its immediate connector. If P0545 persists with the sensor unplugged, the short exists in the wiring between the connector and the ECM.
Can P0545 damage the DPF?
Not directly, but the ECM's conservative response to an absent or invalid EGT signal often prevents active regeneration cycles from completing. Over time, excessive soot accumulation will block the DPF, requiring a forced regeneration or replacement. Early repair protects the DPF.
Is P0545 the same as P0544?
No. P0544 is a general EGT circuit fault (signal out of range, direction unspecified). P0545 specifically indicates the signal is below the low-voltage threshold, pointing to a short-to-ground or a sensor whose resistance has dropped too low. This distinction narrows the diagnostic focus to ground faults rather than open-circuit faults.
How do I know if the short is in the sensor or the harness?
Unplug the sensor and measure resistance from the harness-side signal pin to chassis ground. If the short (below ~1 kΩ) disappears when the sensor is disconnected, the fault is inside the sensor. If the short persists with the sensor unplugged, trace the harness toward the ECM to find the chafe or damaged insulation.
Disabling P0545 in software
RaceTune can permanently disable P0545 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
ECUs with a P0545 disable in our catalogue
Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.
- Bosch EDC17C50 verified 1 software version
- Bosch EDC17C74 verified 1 software version
- Bosch EDC17CP09 verified 1 software version
- Bosch EDC17CP44 verified 1 software version
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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