Reading DPFE voltage using OBD-II PID

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stlham59 - 28 Oct 2007 03:19 GMT

I back probed the connector on the DPFE referenced to SIGRTN , Vref =
5V, DPFE = 2.39V (zero delta pressure - both ports open to air). The
DPFE voltage should be < 0.6 volts with a zero delta pressure
therefore the DPFE is defective. I also applied pressure (output
voltage lower) and vacuum (output voltage higher) to the reference
port, this shows the DPFE is still responding but has a killer 2.4V
offset rendering it usless in the application.

I would like to read the DPFE output voltage using my ELM320 scantool
to verify the ECU is reading about the same voltage as my DMM. I had
very good success troubleshooting an intermittent HO2 sensor failure
by logging data using a program I wrote to drive the ELM. But I
cannot find good helpful information regarding the PID for the DPFE.

The best I came up with is this...

>0645

46 45 20 7F 32 CB 40

Mode $06 - PID $45

I replaced the DPFE with a pot and input a range of voltages to the
ECU and tried to correlate this to the ELM response(s) but without
knowing the data position and the bit width it becomes rather
frustrating. The data in the 2 right-most bytes changes when I change
the voltage but I'm not sure if I'm looking at the right data fields.

If anyone can tell me if this is the correct mode and PID and how to
determine the voltage from the data string that would be nice.

Thanks
DC

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Happy Traveler - 28 Oct 2007 07:50 GMT

According to my book, the PID for DPFEGR (in Volts) is 114E (hex, I
suppose). No clue about mode or how to convert the result to volts -- my
scanner just reads this with directly, with no need to enter modes or
anything else...
HOWEVER, unless you are doing this as an intellectual exercise, it's not
worth struggling. Your DPFE is dead -- a very common problem.

...

> Mode $06 - PID $45
>
[quoted text clipped - 4 lines]
> If anyone can tell me if this is the correct mode and PID and how to
> determine the voltage from the data string that would be nice.

...

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stlham59 - 28 Oct 2007 15:19 GMT

Dear HT,

Yes it is an intellectual exercise...

Thanks for the 114E (that's HEX hence the "E") I will give that a try.

BTW, a couple further questions.
1) What book are you looking at?
2) What scanner are you using?

Thanks,
DC

> According to my book, the PID for DPFEGR (in Volts) is 114E (hex, I
> suppose). No clue about mode or how to convert the result to volts -- my
[quoted text clipped - 15 lines]
>
> ...

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Happy Traveler - 29 Oct 2007 02:30 GMT

My source of information about those things is the so-called Volume H of the
Ford shop manual, officially called "Powertrain Controls/Emission
Diagnosis". In print it's fairly pricey, but slightly out-of-date versions
can be had for a song on DVD -- together with a bunch of other manuals. Last
time I looked Ebay was flooded with those.

I am using an EASE scanner. Bought it quite a few years ago. This company
addresses mainly the professional market, and their DIY line seems both
overpriced and under-capable today. I never upgraded it with their 'body and
chassis package', because it would have been a fortune. There almost
certainly are better choices today. In fact, I am looking at AutoEnginuity
(sp?). If anyone lurking here has experience with those, primarily with
their extended capabilities like ABS, climate control, etc, I'd like to hear
from you.

> Dear HT,
>
[quoted text clipped - 3 lines]
> 1) What book are you looking at?
> 2) What scanner are you using?

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