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Torque » Torque OBD ECU Scanner » Torque Discussion / Ideas » Manifolf Air Pressure stop at 255 kpa

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Author Topic: Manifolf Air Pressure stop at 255 kpa
S0LlDSNAKE
Member
Posts: 49
Post Manifolf Air Pressure stop at 255 kpa
on: January 3, 2021 (GMT)

Hi every one,

I have a ’08 SAAB 93 TTID (Z19DTR).
When I use the standard PID for Intake MAP, the value displayed increase to 255 at his maximum value never above…

I read that it’s a common issue with OBD II apps, but I don’t know what to set in equation formula to get a accurate value for my MAP sensor.

I read in the WIS :

So I have to create a Custom PID with 010B, and set new equation…
But with which demultiplicator ?

Could you help me to understand?

(I’m really new in this world)

Thanks !
Capp777
Member
Posts: 2993
Post Re: Manifolf Air Pressure stop at 255 kpa
on: January 3, 2021 (GMT)

Its likely you will need a custom pid
if your vehicle doesn’t support 0170
or 0187 pids.

The scaling for 010B is fixed by standard
which apparently not used by your
vehicle (single byte resolution).
S0LlDSNAKE
Member
Posts: 49
Post Re: Manifolf Air Pressure stop at 255 kpa
on: January 3, 2021 (GMT)

Thank you Capp777.

It’s not possible to use the standard PID 010B in custom PID and just change Scale or range?

If I use PID you say, what equation to use ?
Capp777
Member
Posts: 2993
Post Re: Manifolf Air Pressure stop at 255 kpa
on: January 3, 2021 (GMT)

If the vehicle supports the other pids, a
quick web search should help with the
equations. I would think KOEO should
match atmospheric conditions…

I also believe the 010B pid wouldn’t
handle the full voltage range needed.
But as always could be wrong.
S0LlDSNAKE
Member
Posts: 49
Post Re: Manifolf Air Pressure stop at 255 kpa
on: January 3, 2021 (GMT)

Thank you again, I’ll try tomorrow, and get back to you. 😉
moreause
Member
Posts: 637
Post Re: Manifolf Air Pressure stop at 255 kpa
on: January 3, 2021 (GMT)

i had the same issue like stated, no you cannot use the standard pid and change the value

the standard is 1=1 kpa if i remember correctly

some car will roll over ..256=1
some car will just stop at 255

you have to find another PID that will do the full range , if it exist

in the past i used an arduino to measure the voltage directly and send the data into the bus …

but i finaly found the PID so got rid of the arduino

ps why 255 because the value is outputed in a 00 to FF format in HEX that as a maxium value of 255

S0LlDSNAKE
Member
Posts: 49
Post Re: Manifolf Air Pressure stop at 255 kpa
on: January 4, 2021 (GMT)

I’ve tried 0170 and 0187… No data sent back… :-/
Hiej
Member
Posts: 173
Post Re: Manifolf Air Pressure stop at 255 kpa
on: January 4, 2021 (GMT)

Hi,

have had similar “issue”, following the datasheet of MAP sensor of my car is possible to read pressures from 27 to 400 KPA.

using this equation I can read pressures over 255 KPA:

A+256*(1-((24-A)&256)/256)

more details here: https://torque-bhp.com/forums/?wpforumaction=viewtopic&t=2894.0

– – – – – – – – – – – – – – – – – – – – – – –
2010 Mazda 2.2d – 185
OBDLink MX – SGS7
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S0LlDSNAKE
Member
Posts: 49
Post Re: Manifolf Air Pressure stop at 255 kpa
on: January 5, 2021 (GMT)

Hi Hiej,

Thank you for your help.

I had see your thread during my searchs before posting.
But your issues seems not really the same as mine.

Your pressure go on after 255, with 1 for 256, 2 for 257 and so on…

But in my case, it stop at 255 kpa.

So, I don’t think that your formula could work for this problem.

Hiej
Member
Posts: 173
Post Re: Manifolf Air Pressure stop at 255 kpa
on: January 5, 2021 (GMT)

a solution could be to find the PID that shows the Volts value of your MAP sensor (Hope it exist), then you can transform Volts to KPA applying a formula knowing that 4.65V = 300KPA and 0.40V = 20KPA.

– – – – – – – – – – – – – – – – – – – – – – –
2010 Mazda 2.2d – 185
OBDLink MX – SGS7
– – – – – – – – – – – – – – – – – – – – – – –
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