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| 96bowtie | 96 PCM to cluster communication question | ||
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Guru Newb
 
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Looking for anyone who knows anything about the serial comm between the dash, ASR module and PCM.
There is a pair of wires that provide serial data to the car. Does anyone know the language/protocal and if the info is transmit from the PCM or or transmist and recieveback from the separate modules. Working with aftermarket ECM options and need to keep functionality of digital readouts on dash. Thanks |
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Posted on: 2012/5/2 18:27
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
 
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In short.... Good luck with that.
I am remote now. Let me put some thought to why and why not... When I get home I will download! |
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Posted on: 2012/5/2 19:48
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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I am back!
Here is the complexity... The CCM is expecting data in some format. I am not sure what that format is, but it is expecting it. It is some kind of data stream. Could it be binary? ASCII? EBCDIC? Something else entirely different? Who knows. I don't. The scanners are reading data FROM the CCM, but that is already translated into an ASCII data stream. What this means is as follows: You would need to be able to translate the data from the aftermarket controller into a language that the CCM will understand. That is the trick. So you need to know what the aftermarket ECM is doing and what the GM CCM is doing and make the two agree upon something. It also means that the signal has to be right, not just is it the right data, but is the data carrier signal correct. Is the voltage right, speed... you name it. It would be a pot load easier to do quality, accurate aftermarket gauges than it is to keep the CCM. At the same time, you can go old school - 1989 - keep the ABS system, but lose the ASR. Short of running the existing ECM as a piggyback, simply to read sensors, I don't know how it can be done. At which point the ECM would need to send to the CCM the following: TPS IAC MAT/MAF VSS RPM Everything else, including DTC's, would have to be turned off. Exciting, eh? If you are looking at an aftermarket ECM, take a close look at www.eficonnection.com. These guys are doing full on LSx ignition systems on old school Gen1 and Gen2 motors. |
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Posted on: 2012/5/3 0:28
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| 96bowtie | Re: 96 PCM to cluster communication question | ||
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Guru Newb
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Thanks for the reply.
One of the large questions I need to understand is if the data is transmit and receive or just transmit. Thanks |
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Posted on: 2012/5/3 19:25
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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Well... it's like this. In the GM world, the data is 2 way. The PCM is looking to the CCM for VATS.
The ASR and ABS are looking for data from the CCM, too. There is the 2 way part of this deal. |
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Posted on: 2012/5/3 20:29
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| Ultraman | Re: 96 PCM to cluster communication question | ||
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Welcome to the Guru! Would like to see some pics of your car when you get a chance.......
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Posted on: 2012/5/3 21:26
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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What year? And why the desire to go aftermarket?
The later 94+ PCMs are programmable, and have built into them various tables that make street driving acceptable. You may not find that luxury with an aftermarket system. I read in Forza (Ferrari mag) several months back, some guy had a carb'd 308, 1979. Sweet ride, but he lived at high elevation, near Sonoma AZ and drove down to Flagstaff on a semi regular basis. The old school points/condenser/carb system balked and required retuning every time. So he went aftermarket and installed an Electromotive ignition and some other aftermarket EFI using TWM throttle bodies and I think a Bosch based computer, but I don't remember that. Regardless, he was having idle, throttle tip in and other drivability issues that won't go away anytime soon. Just saying that sometimes factory junk is the best way to go. |
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Posted on: 2012/5/3 21:43
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| 96bowtie | Re: 96 PCM to cluster communication question | ||
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The PCM is a 162143999.
The general has the best overall programming and intergration into the car, however engine management has evolved. Look at how lsx's are being managed. Imagine real time tuning? Wide band input into PCM, high resolution timing and fueling tables, the possibilities are endliess. The challenge is the integration into the rest of the car. I am not here to tout a particular brand of engine management, however just looking for info on the comm between the components. I highly doubt gm invented their own comm protocol, so it's probably an existing protocol or series like data line. Also. I've seen allot of people become frustrated with aftermarket setups. Some are better than others, however keep in mind the drivability issues are usually the tuner or the softwares inability to allow you to tune transitions/transients in engine changes (fuel, air, speed, load, etc) Just need to find out more. |
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Posted on: 2012/5/4 19:10
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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Do you wanna bet money they didn't? One of the things that kept GM in business was their engine management.
I know, for example, that Chrysler used a multiplexed busing system to move data from pillar to post. Each sensor know which packet was it. GM is just as proprietary... I will say this, for the most part, the gauges are analog, so they are being sent a voltage out of the CCM, the problem? What is the data flow to the CCM. You may want to quiz the gents at our sponsor, K&B Corvette Products... or the guys at Dakota Digital. I have already asked the guys at www.eficonnection.com, and they know nothing... at the same time, their comment was "That's GM secret squirrel stuff" (paraphrased). I understand the advantages, just be aware of the pitfalls. If you can get some info, perhaps we can make something of a translator. I see the need... But the key is knowing the stream coming out of the ECM and what the CCM is expecting to see. |
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Posted on: 2012/5/4 19:46
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| 96bowtie | Re: 96 PCM to cluster communication question | ||
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Guru Newb
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Someone knows or has reversed engineered it.
The quest for more info ensues....... |
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Posted on: 2012/5/5 6:01
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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oh, believe me, I have asked around.
No one seems to care about the comm between the ccm and the ecm on these things. Now, don't get me wrong, I wish you all the luck in finding this out, because I would be one of the first to take advantage. Reach out to the guys at tunercat pro... they might have more answers than we realize. |
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Posted on: 2012/5/5 15:04
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| vis_croceus | Re: 96 PCM to cluster communication question | ||
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Senior Guru
 
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On one of the old DIY tuning forums from the 90s there was some info on many of the GM datastreams. It may still be on the net somewhere.
For the streams being discussed here it was only the most rudimentary outline of message headers, checksums, etc. but not message content. There are only two ways you'll get that info: - find a retired GM engineer who worked on it and saved some documents - reverse engineer it yourself |
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Posted on: 2012/5/7 4:02
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| 96bowtie | Re: 96 PCM to cluster communication question | ||
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I am thinking the reverse engineer methods will yield more results. May have to try scoping it out and getting a reference point.
The quest goes on! |
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Posted on: 2012/5/7 21:16
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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you will need to see if the stream is binary or whatnot.
It is considered a serial data line, so it might be series binary, then translated into ascii by the CCM. I still think you need to reach out to K&B Corvette products and pick the brain of the guy that does the tech work. |
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Posted on: 2012/5/7 21:24
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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one more thought... Guldstrand did this... I just ain't sure how he did it... but, they did an LS6 into a 92, and used the 92 ECM as a data sender to the CCM. In short, they programmed out all of the functions, but left the ones that send data to the CCM and associated things.
It was in Corvette Magazine, at least 2 years back now... Try 3 years! March 2009. If you want a copy of the story, I am pretty sure I can get one. |
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Posted on: 2012/5/13 4:11
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| 96bowtie | Re: 96 PCM to cluster communication question | ||
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The 800 data stream should be some form of serial.
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Posted on: 2012/5/15 2:42
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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that's great... but serial what? ASCII? Binary? ANSI? It didn't have to be anything, there is no standard for internal communications.
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Posted on: 2012/5/15 3:01
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| 96bowtie | Re: 96 PCM to cluster communication question | ||
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Well it it is no revaluation, but the standard for the comm has to be out there because various scanners will communicate with the components. For example a tech 2 would have the protcol programmed and we just never see it or discuss it.
Possibly a derivative of or j1979 protocol itself. Or j1850. K&b corvette did not know anything about it and I even spoke with Gordon killebrew also of this. Not a very common subject matter. Looks the guru forum is short on this one. |
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Posted on: 2012/5/15 15:34
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| Matatk | Re: 96 PCM to cluster communication question | ||
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So an automotive electronics rebuilder didn't know anything about it....one of the premiere world experts in the C4 didn't know about it...you state it's not common subject matter...but the guru fell short on this one....  |
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Posted on: 2012/5/16 2:22
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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took the words right out of my mouth...
Let's review the way the system works, I am using 1992 as the example, all years, 1990-1996 are similar. My latest round of research has been, to say the least, interesting. The port in question is "M"... and that is the serial data port. And guess what... it shares the exact same data as the rest of the system. It is not getting some composite or what not, it is seeing the same info that the CCM is getting. Which means that the packet data has been decoded... Tunercat has done it... EASE has done it... Snapon has done it. Anyone who has made a program that has read that data to display it, has cracked it. The key now is translating it fast enough so it will be of use or what not. I should have gone back to the FSM sooner... It is also multiplexed or somehow encoded. This way the brake data would stomp all over the engine data... There must be some form of traffic cop or the UARTS simply use a coding method to ignore somethings and display others. I am not sure. But it is obvious someone has made sense of this data. Oh, and didn't I suggest to check with the Tunercat people? Attach file:  1992 ALDL.jpg (28.21 KB) ECM Wiring 1992 .jpg (135.26 KB) |
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Posted on: 2012/5/16 4:04
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| 96bowtie | Re: 96 PCM to cluster communication question | ||
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It is starting look more like it is possibly just an obd2 protocol, however I'll have to put together an rs232 circuit and a controller to test it out.
The 92 print you posted up there is basic example, however the 96 is slightly different, however primary concept is there. To respond you good sir Matatk, just because kb is automotive electronics repair centre does not mean they have fundamental knowledge of the subject matter, I spoke with them and they can program an ecu to have a new vin, but that sounded like the extent of it and when I discussed the information I am chasing, they acknowledged it was way beyond their work scope. All forums fell short on the question not just this one and it has no bearing or marker on the quality of this discussion place. If there is nothing to contribute to the thread constructively I didn't see this is as a soap box for you! |
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Posted on: 2012/5/16 18:25
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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Bowtie - Matt was thinking what I was... Your comment felt like a slam against us... it felt a little out of place and unfair, to be honest.
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Posted on: 2012/5/16 18:37
Edited by bogus on 2012/5/17 1:23:30 |
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| Matatk | Re: 96 PCM to cluster communication question | ||
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Webmaster
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Quote:
This is not a soapbox. I am a webmaster of this excellent forum which is full of good and knowledgeable members. You making an unnecessary derogatory comment thus becomes my business. If you did not find the information you needed, I am sorry that we couldn't help. But being insulting won't help you on this matter nor on any future questions you have. If you have further problems with me, feel free to send me a private message. If you have further problems with the quality of the advice given to you then I suggest you a) provide the correct information in a constructive method or b) refrain from using this forum. Matthew |
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Posted on: 2012/5/16 19:08
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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What Matthew said.
Oh, and I own this place... |
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Posted on: 2012/5/17 18:24
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| vis_croceus | Re: 96 PCM to cluster communication question | ||
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Posted on: 2012/5/18 4:12
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| merlot566jka | Re: 96 PCM to cluster communication question | ||
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Guru Newb
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It uses GM 8192 UART.
From the CCM to the cluster it's LCD data, including the clock(freq) for the LCD. I have discussed this in length on the CF. see the thread titled 24x conversion. Any questions, find me on FB, Oklahoma Corvette and High Performance Electronics Specialist. I have been working on this same thing for a while now. |
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Posted on: 2013/9/10 15:51
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| merlot566jka | Re: 96 PCM to cluster communication question | ||
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On the 96 there seems to be a seperate chip for the Class 2 J-1850 VPW data. This seems to be integrated to be able to communicate with the SPI between the Event and Time HC6800 chips. Then somewhere this chip is able to interface and spit out the trouble codes via class 2. Where as the CCM, ASR/ABS EBTCM, and DERMS still talks on the old 8192 UART bus.
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Posted on: 2013/9/10 15:57
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| Ultraman | Re: 96 PCM to cluster communication question | ||
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Posted on: 2013/9/10 22:41
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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Merlot - good info!
I then wonder... does the tech II use the Class 2 data? And the rest of us are stuck with the RS232 based UART data? |
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Posted on: 2013/9/11 0:08
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| merlot566jka | Re: 96 PCM to cluster communication question | ||
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Yes, the tech 2 uses class 2. It also reads 8192 UART, 160 baud, and CAN. With different expansions, it can read almost any manufactures data.
The rest of you are stuck with the old data, for now. But that old data (GM 8192 UART) is much easier read by a pc. Ie the interface is cheap an easy. Be happy about that. To clairify, GM 8192 UART has nothing to do with PC UART. It also has nothing to do with RS-232, which is just a style of connection. GM 8192 UART is proprietary to GM, and follows guideline writte by the SAE. Those guidelines are public, as is all of the communications protocol for all US vehicles. They are readily available on google. By law they have to be, which was the whole point to OBD2 to begin with. |
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Posted on: 2013/9/11 1:31
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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Agreed on the public nature of the UART... I thought that the 8192 was an old UART chip from days gone by...
I will have to dig into my head as to why that sounds like that. I am not an electronics or computer engineer, what I am is a Systems Analyst, and when you have been around tech long enough, the crap starts sticking to you. Thank's for the clarification! |
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Posted on: 2013/9/11 1:41
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| merlot566jka | Re: 96 PCM to cluster communication question | ||
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No prob. I try to spit out what I know as much as I can. I have been working to find a solution here for so long, that I have seen hundreds of these posts where everyone is asking "what on earth is this". Instead of being the man with the secret, I want to be the man with the big mouth. Information is power. The more powerful WE are, the more WE can succeed. At least, that's how I view it.
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Posted on: 2013/9/11 1:46
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| merlot566jka | Re: 96 PCM to cluster communication question | ||
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For the OP, and I know this is a bit old, but Ill break it down...
The CCM is the master in all comms. The CCM sends out a status update once it's woken. It checks all the players, roll call if you will. It gets a packet of data from the PCM telling all the info you get on your cluster. The data is broken down and re-routed to its appropriate places. A certain part of this is sent out on 5 wires to the cluster. This has a different type of data, made specifically for the LCD. The buttons on your DIC control control the different feeds to the LCD. So on the 96, which uses Class 2 for its diagnostic port, there are two different serial data lines. The CCM talks on the 8192 UART line. The data is generated inside of the PCM and sent out as UART. Which is crazy, because as far as I know, there are few systems with TWO different styles of serial data. The 2004 GTO uses a module to convert the Class 2 into 8192 UART. It's called the PIM. Anyway, once the CCM gets the data it does the rest of the work. Since the CCM is the master, and it does all of the organizing if you will, it has to be there for the rest of the systems to work. (With a new ecm/pcm) So how do we give the CCM what it needs? I don't know. I have an idea. How does the EBTCM communicate with the pcm when you lose traction and it needs to retard the timing and pull the throttle shut? I don't know. Just flat out, no clue. |
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Posted on: 2013/9/11 2:13
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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dude, you have so echoed my opinion, it's not even funny! WE are 100% on the same page. |
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Posted on: 2013/9/11 13:46
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| bogus | Re: 96 PCM to cluster communication question | ||
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Grand Imperial Pooh-Bah
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Quote:
I would think that there must be some sort of priority override. Once the EBCM goes into ASR mode, it overrides things, and sends a warning... OR! And this has always been my guess... the warning is via the throttle pedal... Once the ASR kicks in, it messes with the ASR throttle servo, that causes the throttle to close, which causes the timing to retard. Instead of active control, how about cause and effect? |
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Posted on: 2013/9/11 13:49
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| merlot566jka | Re: 96 PCM to cluster communication question | ||
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It is active control, it does both, retards timing and pulls the throttle. I have seen this in the code, and thought about changing its parameters to create a launch control... But bigger fish to fry.
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Posted on: 2013/9/11 19:46
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| bogus | Re: 96 PCM to cluster communication question | ||
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Good idea, tho...
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Posted on: 2013/9/11 20:01
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