OBDLink

[Mopar1973Man]

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.

[Me78569]

Alright,

 

Update for those guys wanting Boost on their OBD Link  Give these a try

 

early Trucks

(A*2)/7 = Boost reported in PSI

 

Late truck

((A*2) /7) - 11 = boost reported in PSI.

[woodtrucker]

Ok. I read through a lot of this post. Just confirm with me, we are only pinging the ECM and not able to get in there and modify it to the point it trashes my truck! I am a tinkerer and like to try things to figure out software but with this scanner, I certainly don't want to do any damage!  I may need some help! you guys are awesome and I like that you are cracking the cummins code to figure out how to monitor things! It shouldn't be that hard plug up a device and check anything you want but not so much! I'm sure I'll get it figured out...Otherwise I'll be tugging on your coat tails guys! 

[Me78569]

The OBDlink is only able to read the data stream that the ECM and PCM put out.  You are not able to actually flash anyhting.

[woodtrucker]

Here's my first screenshot from a few minutes after start up on iPhone version. It seems a bit different than android as I have not found a place to send commands to ecm but it is communicating. I can do custom PiD's and I'm gonna try to set up boost like you guys have done in the next couple days. Gotta go today and help my father in law purchase a Laramie. Looking in the 2013-2016 range and boy are they some nice trucks. And expensive!!! 

[Mopar1973Man]

Under Settings go to User-Defined PID's. This will allow you to set your own custom PIDs and custom math for them as well. 

[woodtrucker]

10-4! Thanks. 

[woodtrucker]

Question on using the formula's on the wiki page. 

Do I use the min and max values they have listed for the SAE PID's? 

I created a MAP gauge using the latest equation provided. 

I created an APPS gauge (11) based off of the info on wiki

and I did a Timing Advance (before TDC) using the equations on wiki for PID's. 

Not sure if the timing advance one will work but I just thought I'd try it. 

I'm new to all this and VERY excited to set up a custom dashboard. Gonna try it with the wife get's back with my car and my OBDlink. I left it in there before she left! haha. I'm gonna have trouble keeping up with that thing! 

[Me78569]

Timing wont work, the only ones that will work are the ones that mike posted on the first page. Our trucks don't really follow a standard per say.

[woodtrucker]

I tried ((A*2)/7)-11 and my boost is at about half what it should be. Roughly.

[SpaceHiker]

Mike directed me to this thread because I'm trying to get my OBD hardware/software to pull in as many pids as possible on my 98.5, which apparently has a different arrangement of pids than the newer trucks (01+???)

 

I'm going to make some rough notes here to document what I'm finding, and I'll probably be updating these notes over the next few hours, so please bear with me. When I'm done, I'll clean it up so early model owners can get their OBD systems set up.

 

I also have some comments about the MAP -> Boost project which I'll post later.

 

atsp0 OK>

at h1 OK> (turns on headers)

0100 Searching... 

48 6b d1 41 00 b8 1a a0 14 4b 48 6b 15 41 00 98 3a 80 14 6f

at h0 (turn off headers)

 

Address d1 = PCM ???

Address 15 = ECM ???

 

Device d1: B8 1A A0 14

1011 1000 0001 1010 1010 0000 0001 0100

01 MIL status, # of DTC's

03 Fuel system status

04 Calculated engine load

05 Engine coolant temp

0c RPM

0d MPH

0f Intake air temp

11 apps (throttle position)

13 02 sensors present

1c OBD standards

1e PTO status

 

Device 15: 98 3a 80 14

1001 1000 0011 1010 1000 0000 0001 0100

01 MIL status, # of DTC's

04 Calculated engine load

05 Engine coolant temp

0b Map sensor

0c RPM

0d MPH

0f Intake air temp

11 apps (Throttle position)

1c OBD standards

1e pto status

 

For some reason my OBD setup does not read most of these values, probably because the truck is returning an unfamiliar format. Next I will send the individual PID's to the truck (0105 for instance for coolant temp) to see what the truck sends back. I'll do that tomorrow and update this post with the results.

Edited January 13, 2017 by SpaceHiker

[SpaceHiker]

I also wanted to comment on the MAP sensor to boost pressure project. I'm not sure that's it's possible to do what you want, because I have a feeling the conversion from MAP data to boost pressure requires a table rather than a formula.

 

First of all, we have to consider how our gauges read boost: A typical boost gauge is calibrated to standard atmospheric pressure at sea level (14.7psi = 0 boost), and merely shows how many PSI above standard atmospheric pressure we are currently boosting our intake pressure up to.

 

**************************

Now there is a way around this: Some mechanical pressure gauges have an air channel that equalizes the pressure in the gauge with CURRENT atmospheric pressure, and shows how many PSI above the current pressure we have. If we were to hook up a gauge like this to our intake, the boost numbers would be all over the place depending on the current absolute barometric pressure (primarily based on elevation and temperature).

****************************

 

Ignoring everything in the stars for a moment, the reason a boost gauge is calibrated to standard atmospheric pressure is because our turbos are engineered the same way. They are a pressure equalizing device, so that if you supply a certain amount of fuel+air(temperature) to the exhaust vane you will get a certain amount of air pressure into the intake. And it DOES NOT MATTER what elevation you are at, the turbo will automatically compensate within it's mechanical limits (for instance at low RPM's it can not yet compensate for high elevation, but as soon as you speed up the engine, it will).

 

That's why turbos were known as "Altitude Compensators" when they were first invented. They would allow an airplane to have the same performance at high altitude as they had at sea level, up to the mechanical limits of the turbo, because they would allow the engine to maintain the same intake pressure at any altitude.

 

So what this means for us, is that all MAP sensor data below 14.7psi needs to be discarded, because it means nothing as far as boost is concerned. Now, if you want to translate the MAP data to boost, you would get the most accurate results if you were at a location and time when the absolute barometric pressure (not relative) was exactly 14.7psi or 29.92inHg.

 

Then, you would drive around and look at both the MAP data and your boost gauge. At 1psi of boost, record the MAP data. At 2psi of boost, repeat. Continue on until your boost is maxxed out.

 

Now you have a table of MAP data to boost pressure. From this, it might be possible to come up with a formula if you are a math genius. But I seriously doubt it, my guess is that there are too many variables involved in translating a MAP sensor's absolute pressure data to a relative boost reading.

 

But at least you have a table now, and maybe you can program the table into some kind of software to give you a boost reading.

[Me78569]

I am pretty sure that boost is reported via the SAE standard for early trucks.

 

It would be report in KPA, taking atmospheric into consideration. 

 

(kpa * 2 ) /7

Edited January 13, 2017 by Me78569

[SpaceHiker]

What I've discovered is that I need to manually create custom PIDs in the Torque app for all the sensors that aren't reading correctly.

 

So for example, my Intake Air Temp (pid 05) just reads 0 in the torque app. So I delete that gauge, then go into Settings... Manage Custom PIDS... Add New... 

 

For the pid number I use 01 05

For the formula I use (A-40)*1.8+32 to get the temp in Fahrenheit.

 

I have to repeat this for each sensor that isn't working in torque, but for some reason that fixes it.

 

I've tried the torque app in my other vehicles and all of them work fine, I don't know what's different about the old Dodge. The data all looks the same to me, from car to car. A strange solution, but at least I have data now.

 

19 hours ago, Me78569 said:

I am pretty sure that boost is reported via the SAE standard for early trucks.

 

It would be report in KPA, taking atmospheric into consideration. 

 

(kpa * 2 ) /7

 

The thing that's strange about this is that right now my MAP sensor is reading 101kpa, engine not running. That translates to 29.83inHg.

 

I run a weather station that reports to the NWS and Wunderground and I know that my current absolute barometric pressure is 21.37 and my relative pressure is 30.42inHg.

 

I should also mention that there is no such thing as a standard correction for altitude. For instance, the average pressure at my house on a -26 degree day would be the same pressure as sea level on a 95 degree day.

Edited January 13, 2017 by SpaceHiker

[Dieselfuture]

Does anyone know by a chance which app to use with this OBD link (I have mx)  to be able to read body codes like ABS or SRS I downloaded torque and OBD link app but it only tells me engine related stuff but when I was at parts store they were able to tell me that my SRS light was a belt buckle malfunction

Edited January 13, 2017 by Dieselfuture

[Me78569]

you can't read abs via the OBD bus that obdlinks uses.   need to read it VIA ccd, which needs special coding.

[Mopar1973Man]

Here is my ScanGauge II video of the MAP sensor. This will show you the same thing. The OBDII port isn't exactly usable. 

 

 

[SpaceHiker]

What that reminds me of is microphone correction. Since there is no such thing as an acoustically perfect microphone, a sound engineer that needs an acoustically flat measurement will apply a response correction to the mic's output in order to approximate a perfect response. As long as a particular microphone model can be manufactured with a consistent response, a corrective frequency curve can be applied to it.

 

It could be the same with the MAP sensor. If the engineers came up with a simple and cheap device that changes it's output depending on air pressure, and they could manufacture it consistently, then all they would need to do is place it in a hyperbaric chamber and vary the pressure, recording the readings from the sensor and then entering them into a table in the ECM.

 

In that case, the actual MAP readings need not be linear in any way, as long as they are reproducible.

[jag]

This is a very interesting subject, & the knowledge is outstanding,

But what I don't understand is that the PID's are all relating to something. For instance, say the boost reading is in a PID group under pressure's, so why can't we read the rest of the headers under the pressure PID group like trans gov pressure, or oil pressure?

Same goes for temps, if we can read IAT & ECT, why can't we read the rest  of the PID'S under say the temp PID group. I myself would love to see the Injection pump fuel temp. 

I see on Mads they use PID groups, PID short name & PID long name, but don't use numbers.

OK, now I'm really lost!

[dripley]

I got lost a long time before your post @JAG1