J1850 OBDII FORD SCP PWM Documentation Needed - PIC Project

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anzic

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j1850 pwm protocol

Hi there,

I am constructing a PIC 18F micro project to read diagnostic data and fault PID codes from a FORD OBD-II port using the J1850 PWM protocol, the Ford SCP (Standard Corporate Protocol) variation. This was in use in some Australian and international fords up to about 2000-2002 depending on the model. Its the 41.6k baud version.

I understand that there are specific manufacturer chips from OKI and others to interface to the ford bus, but I want to do it with a PIC and some minor circuitry. Keep it nice and simple.

I have a problem in locating the SAE J1850 document that details the entire pwm protocol so I can develop my software, and also the PID's for Australian Ford Vehicles.

I know the SAE J1850 doc was freely available at some stage, but I am unable to obtain a copy from anywhere. If anyone has a copy it would greatly be appreciated, as would any other info on J1850 PWM SCP. And for the PID's, they seem to vary depending on the country, theres so many different types!

Any help would be great.

Regards,
Anzic.
 

pic obd

Hi Xnox,

I have that one, and it only outlines the basics of the protocol. Unfortunately it does not state the specific data within the data frames, anything about the IFR data, or the node addresses for requesting specific data. so whilst it shows the protocol structure, it isnt that usable to actually do anything unless you have the rest of the information (like the ford SCP codes).

Any of the below would help if anyone has them.. would be Great.

Cheers,
Anzic.


SAE J1850: Specifies requirements for a vehicle data communications
network. Compliance committee recently formed (J1699)
SAE J2178: Specifies non-diagnostic messages.
Part 1 - Message header formats and physical node addresses
Part 2 - Message parametric data
Part 3 - Message assignments for the single byte header format
Part 4 - Message assignments for the three byte header format
SAE J2012: Diagnostic Codes
SAE J2190: Specifies diagnostic and malfunction messages (to “fix” vehicles)
SAE J2008: Recommended Organization of Vehicle Service Information
SAE J1978: OBD - II Scan Tool (On Board Diagnostics)
SAE J2205: Expanded Diagnostic Protocol for OBD-II Scan Tools
 

j1850 pwm

Ahh, I see... Interesting subject.

I have two friends in the motor vehicle manufacturing business that might be of help - but they are both on summer vacations
so I'd have to ask them in a month's time or so.

/Ram
 

ford j1850 pwm

Thankyou for that, it would be most appreciated.

It is typical of Ford to use a proprietary protocol in such a manner. Im primarily aiming at reading engine running data for display, and reading and clearing PID fault codes. I bought an ELM327 and that just flat out would not connect as it apparently does not read the altered "Ford SCP" version of the J1850 PWM OBD protocol.

Thanks again. The hunt continues

Anzic.
 

ford scp protokol

You may need SAE J1850 for Chip design, and SAEJ1979 for communication protocols.
You can download those documents on SAE webpage, however you may need to pay the annual membership fee for that.

SAE J1979 defines all the PID fault codes and dynamic data display information including their conversion tables.

All the vehicles running in North america must follow the SAE regulations, not just Ford but others as well.

I am not sure if I may post that document here or not.
 

obdii project

Hi Sahn,

Thanks for that. Most helpful. I know the documents were available at no cost on the net years ago...

If you could post these docs, it would be great, or pm me. Very grateful.

Thanks,
Anzic.
 

j1850 frame structure

You will find an example here: http://obddiagnostics.com/

Download the schematic. These people sell the pre-programmed PIC (a 16F84). But if you want to develop your own code, then you can use their schematic (like I did) and program your own PIC. I changed to PIC16F876A, because it has a built-in UART, more memory, etc.
 

j1850 pwm pdf

VVV,

thanks for that link. there was a bit of useful information there.

Unfortunately, Ford with their SCP version of the J1850 pwm mangle the signal by using different sequences and a different frame structure to the normal protocol. Whilst the interface was pretty standard (similar to ELM327 interface), its more the code im after.

Specifically, PIDs, DTC and node information. I wouldnt mind the paper on SAE J1850 for verifying the design, and the J1979 paper to make sure at least the frame data is correct, then just need the proprietary ford data to make it all work.

Anzic.
 

ford scp ifr

VVV,

Thanks for your help. Without info on how to query for engine data (node ids and stuff), and what the IFR responses should be, looks like this project will only be half done unless I can get my hands on some of the SAE stuff, or a ford/scantool expert is willing to help out.

Thanks for the trouble codes, at least thats a start.

Who would have thought making your own scantool would be so hard....

Anzic.
 

pic obd2 project

Check out this link

https://obddiagnostics.com/obdinfo/info.html
https://obddiagnostics.com/obdinfo/msg_struct.html

That includes a lot of what you need to know.

And here is an example of what the data should look like when it works.
https://obddiagnostics.com/obdinfo/pwmmode1.TXT
Ignore the control byte and the frame number.
As I recall on my 1998 Mercury there were slight differences in the number of bytes returned by the vehicle in response to some requests, but it worked.

To test your tool, just send one of the frames given in the example: 61, 6A, F1..... If all goes well you should get back a response and you'll go from there.
 

j1850 pwm schematic

Thanks for that, will give it a try.

If anyone else has any more info or SAE papers, please feel free to contribute to this interesting project.

Cheers,
Anzic.
 

j1850

If anyone has a PDF copy of the SAE J1850 paper or related, it would be a great help.

this project has stalled without that information unfortunately...

Anzic.
 

ford scp protocol

Hi anzic,

Check you private messages.
 

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    anzic

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obd2 message format

VVV,

Mate you are a champion, thanks so much. I have been looking everywhere for that document its just amazing. I know I might be pushing it, but you wouldnt happen to have any more J docs floating around would you?

Gave you a helped click, thanks again. I will try and keep everyone updated as this progresses, at least now its moving

anzic.
 

diagnostický software pwm

Hi everyone,

I would like to also include in this project the ISO9141-2 protocol (Which is used on some Fords) but I cant seem to find a copy of the ISO document anywhere. I believe that this protocol uses the K line and handshakes at 5bps and then shoots up to 10kbps. And can also be used with a VPP line to program the ECU? sound about right....?

If anyone has it and can send it to me I would be most grateful. Hope to share all the results of this project once finshed.

Cheers,
Anzic.
 

j1850 pwm protocol scp

Hi,

Sorry to resurrect an old thread, but I would like to know how this worked out? Did you finish your project?

Is there still a copy of the J1979 document around? I am embarking on a programming project myself and would like this documentation.

Thanks for any help,

C
 

Re: J1850 OBDII FORD SCP PWM Documentation Needed - PIC Proj

Thanks guys this is very useful. Looking to develope the same application and need to get ahold of the same documentation. Will post what I find.

Added after 1 minutes:

I'm also interested in finding what the update for this project is.
 

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