I am about wrapped up with my latest project, I have made a true Plug-N-Play Megasquirt system for OBD1 cars. This allows the user to remove there factory ECU, and install this new ECU, with MS inside, and everything on the car works as per normal-NO CUTTING ANY WIRES! . Im ready to start working on a new project, and i was looking at the possibilities of making a MS PNP for OBD2 GM cars. The one thing that is stumping me is it looks like these cars have a databus that sends alot of the information from the ECU to the instument cluster. Older OBD1 cars do not have this... they all have independant wires for each guage/light. So, it was easy to build circuits to control that.
Does anyone have any information they can share about this OBD2 Datalink to the cluster? What Protocol is it? Baud Rate? Do you think I could communicate with it Via Hyperlink to try to reverse engineer the register assingments? Anything you can share would be invaluable to move this project along, as its the ONLY thing stopping me from making this a reality. Please help me understand. Thanks.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
If you can find a source for the GM OBD-2 ECU connectors I'd love to see it...
I have... somewhere, a detailed list of OBD-2 messages that need to be sent out to control the cluster. There are a couple parts I haven't figured out how to do, like control the temp gauge, and the mileage, and most of the idiot lights, but I have most of it.
The protocol itself is called VPW (Variable Pulse Width). You can't hook a serial connection into it and sniff the bus, you need a protocol converter. ELM makes chips that do that, and ScanTool.net sells pre-made boxes to allow you to connect a serial cable to the converter box, to your car.
4cyltuner.com - Information Source For 4 Cylinder Tuners
Buy stuff from CarCustoms Ebay! Won't be disappointed!
I have got the connector issue figured out... just look at mine! lol I also found that they are proprietary, and not sold to anyone except delphi, and i have no chance ever on getting them. so, I have resorted to the old fashioned way of desoldering them from stock ECU's. Works just fine for me, and probably cost about the same to do it that way.
I do have contact with a guy who can make any connector you want, you just have to send him and original, and he will copy it, and injection mold you new ones. I'm saving that on the back burner for if this takes off to where I cant keep up by myself, that is one way to reduce my assembly time a little, but at an added cost.
thank you for sharing that info on the protocol. If you have any links you could share, that would be cool, and if not, I can start doing some searching on the net of my own, maybe i can find something that way.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
Im waiting on some parts to arrive from Digikey, but this week ill be making a PCB board that will fit inside of the ECU housing, and connect to the MS DB-37 connector, and route all the signals out to the appropiate pins on the factory connectors. I also have room to use this PCB to install my Speedo Decoder circuit, Fuel pump relay driver circuit, Wideband driver circuit, Injector FET relocation circuits, Knock sensor circuit and Pyro input circuits. Currently Im doing this with all separate boards/ wire jumpering. but if this new PCB works out, it will be a matter of eching them, loading in components, soldering, and sending it out the door! I think that will reduce my assembly time down from 9 hours per unit to about 2 hours.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
They are GM proprietary OBD-II sentences, I found them by using an ELM to scan the bus, then went through the messages one-by-one to see what message did what.
I will try to dig up the sentences that I recorded if I can remember where I put them...
4cyltuner.com - Information Source For 4 Cylinder Tuners
Buy stuff from CarCustoms Ebay! Won't be disappointed!
o great, so you mean they made this WAY over complicated? Someone was trying to justify there job? jeez.
I checked out the ELM scanner chip sets and schematics. So, your getting these data streams by just watching it go by through the ALDL port? if thats the case, then you could surely say that the ALDL OBDII protocol is this VPM. However, do you think this is the same protocol that the ECU is using to talk to the cluster with? just on a different set of wires?
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
Yes, its well published that GM uses VPW, and yes, its the same protocol used to talk to the cluster from the ECU. I verified this because when I re-broadcasted these VPW messages through the ALDL port, the cluster responded. Its not even on a different set of wires, its all on the same bus.
4cyltuner.com - Information Source For 4 Cylinder Tuners
Buy stuff from CarCustoms Ebay! Won't be disappointed!
perfect. that is good to know.
so, next ofder of business, how do you think they accomplish this transmission. Is data coming in from the sensors reconized by the CPU, and then it uses a lookup table such as the way an ascii message is programmed? or do you think the sentences are generated on the fly by the code?
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
I'm sure the sentences are generated on the fly... At least that's how I would (and am) doing it...
Basically the ECU recognizes a sensor value (lets say for example the speedometer), uses the conversion formula to turn the frequency of the signal into the speed of the output shaft, multiplies that by the factor accounting for the tire diameter, and gets MPH (actually KPH) and sends that to the cluster. Its pretty much the same for all the other PID's that are supported by the cluster. The biggest problem is trying to generate the proprietary sentences that GM uses, since they seem to ignore the checksum's and minimum length restrictions in the OBD-2 standard. You also have to be aware that not all sentences used by the cluster come from the ECU, there are things like the BCM in 2k+ cars, the antilock brake controller, (even the stock radio is on this bus), etc. You can pretty much control anything in the 2k+'s at least, I've even managed to turn on and off the door chime and the interior lights.
4cyltuner.com - Information Source For 4 Cylinder Tuners
Buy stuff from CarCustoms Ebay! Won't be disappointed!
speaking of the speedo signal, that was the last thing i fixed for my system. I'll share some info that may or may not be of use to what your doing.
the diff gear has a reluctor ring on it with 29 teeh. i have found out that the OBD1 ECU's take this 29T/rev signal, and divide it by 6. that 1/6 freq is then output to the cluster in the form of a 5v square wave sink.
maybe something there will be of use to you.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
well, after further research, looks like this is probably a no go for me. I can handle understanding / building circuits for communications, but I dont know anything about writing code, so its beyond me. OBD1 cars for me only
damn.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
KKKKKK, dont get mad.. i really did not read anything BUT the plug and play OBD-1 thing....
SO, ever dabble with the 95 ECM? would love to have something like that.
AS far as connectors go.. i can get them.. but they would have no pin's inside.
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
no, i have not done a 95 Jbody yet, but i have done a 95 Nbody (grand am). so, as long as the 95 J is not anything crazy, and your car is a 5 speed trans, i can do it.
The way to find out is i can buy the alldata account for the 95 J, and then check out the wiring scheme. If its like the rest of the line of GM OBD1, which i dont see any reason it wouldnt be, then we could proceed. I ask $700.00 for the MS PNP i make. The price breakdown is...
250.00 for MS1 rev 2.2 Msns-E extra .029v firmware installed, and perform all GM DIS board mods.
199.00 for a Innovate LC-1 wideband kit - Which i will make PNP into your factory harness with weather-pak connectors.
25.00 for GM weather-pak connectors required for Wideband intergration
100.00 for Two custom circuit boards i make. One will decode the speedo signal, and drive the cluster. the other will contain the knock sensor circuitry.
10.00 for USB to serial adaptor cable
15.00 for return shipping to your address
100.00 for my time to aquire all parts, assemble them, and ship. approx 8-9 hours labor.
ALL nessesary Software on CD- Megatune, Megalog viewer, bootloader,
and of course, this unit is upgradeable at any time, during assembly, or years later, with all kinds of extra features. some include Water Injection control, Nitrous injection control, boost control, launch control, 2 step ingnition retarder, sequential shift light controller, staged injection, upgradeable MAP sensor, upto 4Bar is available, TONS of extra features can be implemented.
I would also need you to supply me with a 95 ECU that i could use as a donor. It would be destroyed so i can use the case, Ill install the MS inside of the factory case. Then i will desolder the connectors from the circuit board, and install them into this PNP.
If your still seriously intersted, Let me know, and ill purchase the alldata account for your vehicle, and we'll find out for sure. If this is not sometihng your intersted in, then i wont spend the money on the alldata account.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
and if you can get the PCM BOARD side connectors, even if they do not have pins, I would be interested in hearing about it.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
well, let me get it running better, and maybe put the motor in a better looking shell...
anyways, know anyone that wants a 95-98% 92 GTZ shell?
ill talk to GM and see if i can get the ECM side of the connectors...
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
can you do this for a 92 cavi 2.2 5 speed
ive done all i can without tuning and that ecm is untunable at the moment (from my understanding)
i dont have time to do all the wiring to the car so this would b a great help
i would want just one change though ..... ill need to use diff injectors (ill have the ones that im gona use befor i get this done though so youl know witch ones im using )
thanz
yes, i can do ANY GM OBD1, no matter the engine. The only requirements is it must be a 5 speed trans.
MegaSquirt is fully programable, at any time, so you can pick and choose your injectors at any time you like, that is no concern of mine. I am not offering any type of tuning service, i am simply aquiring, and assembling the harware, software and firmware, and all nessesary support equipment, so you can install, and begin tuning your own car yourself, without having to learn electronics, soldering, etc. All you have to do is plug it in, and start tuning.
On that note, do not expect to plug the MS in, and just start the car. it does not work like that. you will have to write your own program from scratch. I can guide you through this process, but i cannot do it for you. it will not come preprogrammed for anything. Tuning in a motor is difficult, and will probably be one of the hardest things you will ever do if you have never done it before. I cannot stress enough to read the MegaManuals as much as possible before commiting to it. It is a very real possibility to totally destroy your engine with this equipment package if YOU DO NOT UNDERSTAND ENGINE TUNING THEORY. And that is why i cannot get into tuning your car for you, its too much liability. You must take that responcibility yourself.
I have been working with MS for about 2 years now. I feel i have a very good handle on it. I have tuned in both N/A and S/C'd Quad 4's, Chevy SB, and DSM engines. I have learned the ropes, and i can be available to help guide you based on my experience. but ultimately, the decisions are yours to make.
If you see my words as daunting, then MS is not for you. However is what i said seems like a challenge you would like to undertake, and you would enjoy learning how to tune an engine in the right way, then I would be glad to work with you.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
yea i could do it myself ( im currently just about to grad from a highperf teh school ) i just dont have the time to do all the wiring ( car is at parents 2,5 hours away ) and to tune it to bring home
and for the injectors i was refering to high imp vers low imp ( i was woried about the inj drivers in the board
Oh, I see.
MS can drive 16 High impedance injectors -or- 4 low impedance injectors in its "standard" build. There is no hardware that will need changed if you wanted to switch from one to the other on a 4 cylendar.
M90'd Built LGO-15 PSI
http://webstarts.com/quadper4mance
