Ok gang... I'm going to share a few tidbit of information for advance OBDII tinkering.

 

If you happen to have a OBDLink or ELM327 tool you should be able to tag along here. I will have to give a bit of thanks to @Me78569 for getting me started with the Bluetooth terminal on Android. Once I had that I could directly communicate with the OBDLink and pass commands to it. So starting out I passed the command...

 

ATSP0

This basically tells the tool to communication with the detected protocol of the vehicle ours happens to be ISO 9141-2 protocol. After that I passed the command...

0100

Which happens to be PID Mode 01 with the PID 00 which tells the vehicle to report back which ODBII PID are available. It returns back.

41 00 98 3A 80 14
41 00 90 18 80 14

 

At this point the hexadecimal bytes you want are 98, 3A, 90, 18...

 

So now you need to take these 4 bytes on convert them to binary.

 

98 = 1001 1000

3A = 0011 1010

90 = 1001 0000

18 = 0001 1000

 

So now lay it all out in one long string. This is counting 20 hex (32 dec) from left to right.

 

1001 1000 0011 1010 1001 0000 0001 1000

 

So you have counting only the high bit (1's)...

 

01 - MIL Status Light

04 - Engine Load

05 - Coolant Temperature

(11) 0B - Manifold Pressure

(12) 0C - RPM

(13) 0D - MPH

(15) 0F - Intake Temperature

(17) 11 - APPS Sensor

(20) 14 (Unknown yet)

(28) 1C - OBD Compliance should report 05 hex.

(29) 1D - (Unknown yet)

 

NOTE: (number) is decimal... Just for the human side for counting placement. ECM/PCM use the hexadecimal values only.

 

Now if you want to add any of these as a custom gauge.

 

Module/Header: 486

OBD Mode: 01

PID Number: (Any of the above will work use only the Hex number not the decimal)

Priority: Leave on High

Equation: Look it up on Wikipedia at https://en.wikipedia.org/wiki/OBD-II_PIDs

 

 

 

 

Edited May 27, 20168 yr by Mopar1973Man

My live data for map shows with key on and engine running or not 101Kpa (14.65psi) @ 700'.

Why are you adding 2psi for altitude?  I thought that as you go up in altitude, atmospheric pressure decreased.

You have to minus the total of sea level plus altitude.

 

I need to get the equation more exact.  The above isn't right

 

((A*.145)-16)*4 is working close ishm. The .145 needs to be modded and then increase 16 to 17 for me.

I'll see if I can set baud to 7812.5

5 minutes ago, IBMobile said:

My live data for map shows with key on and engine running or not 101Kpa (14.65psi) @ 700'.

Why are you adding 2psi for altitude?  I thought that as you go up in altitude, atmospheric pressure decreased.

Err you are right though. Back into math world to figure it out.  Point and shoot blindfolded

Sea level pressure today in cos was 1017.0 millibars.  

 

https://en.m.wikipedia.org/wiki/Pressure_altitude

This thread is like reading a different language!

 

Let me know when I can tweak my settings in the OBD link to get accurate boost readings

5 hours ago, notlimah said:

This thread is like reading a different language!

 

Let me know when I can tweak my settings in the OBD link to get accurate boost readings

 

This is like machine language of a 6502 processor of a Atari 800 computer.

well a little more testing was one on the map sensor.

 

 

((A-105)*.17) *4 gets VERY close for a early truck  but I am still testing more.  I am not sure where the quad limits boost at as I am unable to top 13-14 psi on the ecm side of things but boost levels follow pretty close to that point.

 

for some reason you need to use the inverse baro reading so rather than 11 psi where I am at for baro you need to minus 14 -(-baro) ,  don't ask me why.  

 

 

Edited June 1, 20168 yr by Me78569

Alright more testing done and I can verify that 

 

((A-105)*.17)*4 reads nearly 0 at idle and accurately all the way up to the boost fooler limit of 18psi on my truck.  The 105 will need to be edited for your altitude, and I can't answer why it is 105kpa vs 75kpa for my altitude, but it works.  

Mike,

 

What do you get when you pas ATMA to the truck?  anything?

more updates. 

 

I have found the ablity to connect to both ECMS,  The bad news is, if you thought the ecm was lacking for PID's the PCM is worse.  It has speed, TPS, rpm , load.  There may be more hidden pid's but I am unsure about it.

 

The PCM is D1

and the ECM is 15 according to the logging.  Not sure how that translates to 486 

 

Snippet from the log

Quote

ATH1: [OK]
Reading vehicle information
01 00: [48 6B D1 41 00 90 18 80 14 01 
48 6B 15 41 00 98 3A 80 14 6F ]
Detected PIDs:
    ECU: D1
        0x00 - SupportedPIDs0
        0x01 - MonitorStatus
        0x04 - EngineLoad
        0x0C - EngineRPM
        0x0D - VehicleSpeed
        0x11 - ThrottlePosition
        0x1C - OBDStandard
        0x1E - AuxiliaryInputStatus
    ECU: 15
        0x00 - SupportedPIDs0
        0x01 - MonitorStatus
        0x04 - EngineLoad
        0x05 - EngineCoolantTemp
        0x0B - IntakeManifoldPressure
        0x0C - EngineRPM
        0x0D - VehicleSpeed
        0x0F - IntakeAirTemperature
        0x11 - ThrottlePosition
        0x1C - OBDStandard
        0x1E - AuxiliaryInputStatus

 

attached is the log for the data logging from the app.  It is very useful, OBDwiz

 

It allows for you to data log raw data, but it seems to only pass MPH request, not sure why.  

 

 

 

I can confirm that there is no j1939 in the OBD port, or if there is it is no standard in anyway.  I believe the j1393 is only under the hood.  I might try and connect to that at some point.  

 

I am confused on this next part, but

 

Looking at the wiring diagram I see 

 

The SCI bus is iso 9141 10.4k baud ( what we can talk to the ecm/pcm over.)

The CCD is who knows on 7812.5 baud and 62500 baud, I don't think we are going to find the ability to talk on this bus.  

 

 

HOWEVER reading through the logs of the project from Jdonoghue he states that he programmed the ecm using the SCITX and RX pins on the OBD Pins 6, 7  

 

I am guessing that since pin 6 ( the non-standard pin for iso 9141) points to the ecm but 14 ( the standard pin for iso 9141) that all of the obd scanning tools we use are looking to 14 as it is the standard.  This might be why we are having issues.  Again I might wire my arduino to pins 6 and 7 to test.

 

Question I still have is how we can talk to both ECMS on the same protocol but use different pins on the OBD,

 

Note that the PCM and ECM share the SCI transmit wire, pin 7, but SCI Recieve on the PCM is pin 14 and on the ECM is pin 6.  

 

Since they use the same transmit wire they have to be the same protocol, but I am unsure how the header changes which wire is used.  

RawDataLog_20160601 214447.txt

Edited June 2, 20168 yr by Me78569

mike,

 

It occurs to me that the map sensor calculator in the scipod software was based on a late model truck

 

 

What happens if you set your equation to 

 

(A-105)/20  ?  105 being the approx inverted atmospheric pressure.

I'll try that in the morning... I got to head to McCall for groceries.

 

did that equation do anything?

Trip got canceled and alternator repair done so the truck didn't go any where yesterday really. I'll plug it in this morning and see what your math shows. I did get a chance to see the difference in readings early to late models. 14.9 PSIa (99 Dodge) compared to 28.3 PSIa (02 Dodge).

(A-105)/20 doesn't even come close. Starts at 4.5 PSI and at max boost its 7 PSI.

 

Humm I wonder why the scipod was using / 20 unless the ecm reads it differently then translates to the obd standard for the pcm / obd. 

 

 

Mike,

 

Try this equation

 

(a * .145)/4 

 

.145 is the KPA to PSI conversion and / 4 takes the scale from 0-1023 to 0-255

Mike,

 

How we know that the header 486 is the ecm and no the pcm?

On 7/7/2016 at 5:06 PM, Me78569 said:

Mike,

 

How we know that the header 486 is the ecm and no the pcm?

 

Good question?

EDIT: Just thinking about it a bit. MAP sensor is only on the ECM so why would a PCM header respond with data?

Good point, thanks.  

 

Just trying to keep stuff straight.

Had me thinking for a bit then it popped in my head... I need to verify the ECM header as well as figure out the other headers in the system like the ABS, PCM, etc. That would help us out.