P0545: P0545 Diagnostic Guide

What this code means

P0545 may indicate a low signal from the bank 1, sensor 1 exhaust gas temperature sensor circuit.

What the vehicle may do

The vehicle may turn on a warning light.
The concern may be intermittent if wiring or connector contact changes with heat, vibration, or movement.
Exhaust temperature readings may be unreliable when the fault is active.

Possible fault areas

Possible exhaust leaks or exhaust contamination concerns.
Possible EGT sensor circuit, connector, or harness concerns.
Possible EGT sensor concern.
Possible PCM-side concern.

Diagnostic path

Set up the P0545 diagnosis

On this F-150 2.7 EcoBoost, P0545 may point to a low-voltage signal from the bank 1, sensor 1 exhaust gas temperature sensor circuit. The truck may have a warning light, exhaust temperature readings may be unreliable when the fault is active, and the concern may show up intermittently with heat, vibration, or connector movement. Broadly, you’re looking at possible exhaust leaks, EGT sensor wiring concerns, the sensor itself, or, less often, a PCM-side issue. If other codes are present, check what they mean first, but for this one we’re staying on the P0545 EGT sensor path. This code sets when the PCM sees exhaust gas temperature bank 1, sensor 1 voltage less than 0.10 volt for greater than 15 seconds.

Start with the exhaust inspection

Start with the basic system checks, then confirm the EGT sensor code is actually present. If it is, move into the exhaust inspection before touching the wiring. With the ignition off, look for leaks at the exhaust flanges and gaskets, punctures or cracks in the catalyst, punctures or cracks in the particulate filter, and any engine coolant or oil contamination. If you find a concern there, repair what is necessary, clear the PCM codes, and repeat the self-test. If the exhaust inspection is clean, continue into circuit testing.

Check for an open in the EGT circuits

Next, check the EGT signal and signal-return circuits for an open. Only measure the circuits that apply to the vehicle in front of you. With the ignition off, disconnect the PCM connector and measure the applicable EGT signal and SIGRTN circuits. The decision point is resistance less than 5 Ω. If the circuit does not meet that, repair the open circuit, clear the PCM codes, and repeat the self-test. If it passes, keep moving through the electrical checks.

Check for shorts on the signal circuit

If the open-circuit check passes, check the EGT signal circuit for a short to ground or SIGRTN. The resistance should be greater than 10000 Ω. If it is not, repair the short circuit, clear the PCM codes, and repeat the self-test. If that check passes, turn the ignition on and check the EGT signal circuit for a short to voltage. If any voltage is present where it should not be, repair the short circuit, clear the PCM codes, and repeat the self-test. If no voltage is present, move on to the intermittent check.

Run the intermittent harness check

For an intermittent short or open, reconnect the applicable EGT sensor connector and the PCM connector, start the engine, and let it reach normal operating temperature. Monitor the correct PCM temperature PID for the sensor you’re testing, record the current temperature PID value, then set scan tool limits around that value: the lower limit is 30°C (54°F) below the recorded PID, and the upper limit is 20°C (36°F) above it. Now do a thorough wiggle test from the PCM connector to the EGT sensor connector, and tap lightly around the sensor to simulate road shock. If the PID goes outside the limits you set, repair what is necessary, clear the PCM codes, and repeat the self-test. One important caution: if any EGT sensor connector was disconnected with the ignition on and engine off, reconnect the sensor, turn the ignition off for 30 seconds, and do not crank or start until that 30 seconds has passed. Skipping that can create a 60 minute no crank, no start condition.

Check EGT sensor performance on a drive

If the intermittent harness check does not show the concern, check EGT sensor performance while driving. Monitor the EGT temperature PIDs and drive at several steady state speeds above and below 50 km/h (30 mph). You’re watching for the EGT11 or EGT21 temperature to ever exceed 950°C (1740°F). If it does, check the circuits for corrosion or loose wires, wiggle the harness to try to recreate the concern, repair what is necessary, clear the PCM codes, and repeat the self-test. Also remember that regeneration can happen during normal operation and can bias diagnostic values. If regeneration occurs during testing, let it finish before continuing. If manual regeneration is ever involved, the exhaust gets hot very quickly; the vehicle needs to be on the ground and the tailpipe area kept clear of people, obstructions, foreign material, and other items.

Check EGT sensor resistance

If the drive check does not show excessive temperature, check the EGT sensor resistance with the ignition off. The decision point here is resistance greater than 80 Ω. If the resistance is not greater than 80 Ω, install a new EGT sensor, clear the PCM codes, and repeat the self-test. If resistance is greater than 80 Ω, continue to the disconnected-voltage check.

Check disconnected EGT sensor voltage

For the final EGT operation check, turn the ignition on and monitor the applicable EGT voltage PID with the EGT sensor disconnected. The PID value should be greater than 4.7 V when disconnected. If it is, the system is operating correctly at this time, and the original concern may have been caused by a loose or corroded connector. If it is not greater than 4.7 V, check for a loose connection and damaged or corroded terminals, then wiggle the harness to try to recreate the concern. Repair what is necessary. If no concern is found during the visual inspection, install a new EGT sensor, clear the PCM codes, and repeat the self-test.

Use the pressure-sensor path only when those codes are present

If related particulate filter pressure sensor codes are also part of the job, handle that as a separate pressure-sensor path instead of mixing it into the P0545 EGT checks. If the PCM was reflashed, reprogrammed, or replaced before entering that path, drive the vehicle for 8 km (5 miles) to update the PF PID data. Then, with the ignition on, confirm whether the related particulate filter pressure sensor codes are present. That path is looking at possible pressure-sensor circuit concerns, hose concerns, the pressure sensor itself, or a PCM-side issue.

Inspect the particulate filter pressure sensor connector and hose

Next, check the particulate filter pressure sensor connector and hose for damage. Not all vehicles have every component, so stay with the sensors that apply to the truck in front of you. Disconnect the applicable pressure sensor connector, inspect for pushed out pins and corrosion, then inspect the exhaust-side connecting hose for leaks and the sensor port for restrictions. Repeat that same connector, pin, corrosion, hose leak, and port restriction inspection for each applicable pressure sensor. If a concern is present, repair what is necessary, run the appropriate monitor drive cycle, clear the PCM codes, and repeat the self-test. If no concern is found, continue into pressure-sensor circuit testing.

Check the pressure-sensor circuits

For the pressure-sensor electrical checks, only measure the circuits that apply to the vehicle being diagnosed. Check the VREF and SIGRTN circuits for an open; the voltage decision point is between 4.5 V - 5.5 V. If that range is not present, pause and recheck the earlier reference-voltage and signal-return diagnostic path instead of guessing. If the range is correct, check the signal circuit for an open with the ignition off and the PCM connector disconnected; resistance should be less than 5 Ω. Then check the signal circuit for a short to SIGRTN or GND; the resistances should be greater than 10K ohms. Next, check the signal circuit for a short to VREF; resistance should be greater than 10000 Ω. Finally, with the ignition on, check the signal circuit for a short to voltage. If any of these circuit checks fail, repair the open or short circuit as indicated, run the appropriate monitor drive cycle, clear the PCM codes, and repeat the self-test.

Confirm pressure-sensor operation

If the pressure-sensor circuit checks pass, check for correct operation. Disconnect all the PCM connectors. For each applicable particulate filter pressure sensor, disconnect the sensor connector, inspect again for pushed out pins and corrosion, reconnect the PCM connectors and the sensor connector, make sure the connectors seat correctly, and verify whether the concern is still present. If the concern is still present on that pressure-sensor path, install a new particulate filter pressure sensor in question, run the appropriate monitor drive cycle, clear the PCM codes, and repeat the self-test. If the concern is no longer present, the system is operating correctly at this time, and the issue may have been a loose or corroded connector.

Verify the repair

Keep verification separate from the testing. After any repair on this P0545 path, clear the PCM DTCs, repeat the self-test, and confirm the code stays gone. The takeaway is simple: prove the exhaust is sealed, prove the EGT signal and return circuits are clean, then prove the sensor responds correctly before condemning anything. For more diagnostic training, visit stepdiagnostics.com.