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Mazda 6: Flashing DPF Light

Mazda 6 2.0L

When a customer's car shows a flashing DPF light, it's time to grab your Snap-on Scan Tool to get straight to the fix.

This month's Technical Focus is a Mazda 6 2.0L diesel, 2007 plate, GG chassis, showing the code P2454 (flashing DPF light and MIL illuminated).


To begin, a Snap-on scan tool was hooked up to the vehicle to run a pre-scan code report which can be seen below:

Using Fast-Track® Intelligent Diagnostics, there were no TSB’s relevant to the trouble code.

Live Data showed DPF pressure at 0.0kPa at idle and snap throttle confirming the DPF pressure sensor is not working.

Looking under the Guided Component Tests menu, there was a test for the DPF pressure sensor. After reading the component information, a signiture test was carried out, expecting to see 1V, but found 0.0V on pin 2 (signal wire) at idle. While physically stressing the pressure sensor, the signal voltage did increase to 1V, indicating a probable internal fault within the DPF pressure sensor.

Using guided component tests on the signal wire we see 0V, yet we should expect to see at least 1V.

Following the signal out of range test, it was confirmed that probing pins 1 and 3 have a 5V supply and ground present.

A test which is good to use is checking for a bias voltage on the signal wire, some sensors ‘pull down’ a 5V reference on the signal wire. Unplugging the DPF pressure sensor, a 5V reading was confirmed.


This test indicates the signal wire was not open circuit and the issue was within the sensor

Happy to say the signal wire is ok, and the fault was internal to the DPF sensor.

Service Resets and Relearns with Fast-Track® Intelligent Diagnostics pages:

Once the reset was carried out, the code was erased, a post scan was carried out showing no trouble codes.

Live data looks more plausible as we now have a differential pressure reading.

A signature test was also carried out, 1V at idle, and 1.7V on snap throttle indicating the DPF soot loading may be slightly high but not a concern.

After a road test, no flashing DPF light or MIL illuminating, and no codes returned upon my post scan report.

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