Any Class 2 Serial Experts Check In

[matthud]

I am currently working on a project where I am trying to set the gauge values on an IPC from a 99 Vette, its stand alone outside of a car. I have the circuitry that allows me to send and read the class 2 serial data. I have found some of the commands online and I have been able to get the DIC to display door and trunk ajar. I was hoping someone had access to the data commands to set the water temp, the fuel level, and the oil pressure gauges. Is there someone who has access to a class 2 serial data sniffer that could record the first few minutes of a power up cycle, or is there someone with a Tech2 that can find the commands that set the gauge positions?
Thanks

[matthud]

I was able to find the message formats in the SAE J2178 books, and I am able to command the fuel level, oil level and water temp. But about 5 seconds after I command it, the gauges go back to the failsafe position. This is on a dash that is not connected to the pcm or any other serial 2 device. I believe its because the gauge cluster knows there is no pcm present, and this lack of comm causes it to reset the position. Does anyone know of a way to emulate enough of the pcm messages to the gauge cluster to trick it into thinking it is there?

[LSX378]

I was able to find the message formats in the SAE J2178 books, and I am able to command the fuel level, oil level and water temp. But about 5 seconds after I command it, the gauges go back to the failsafe position. This is on a dash that is not connected to the pcm or any other serial 2 device. I believe its because the gauge cluster knows there is no pcm present, and this lack of comm causes it to reset the position. Does anyone know of a way to emulate enough of the pcm messages to the gauge cluster to trick it into thinking it is there?

Do you send the fuel/oil/temp values continuously in messages or only once?

[matthud]

I have to continuously send them to get the needle to stay steady. Not sure if this is how it really works in the vehicle.

[LSX378]

I have to continuously send them to get the needle to stay steady. Not sure if this is how it really works in the vehicle.

And after 5 sec of continuous messages they reset again?

Typically GM cross checks messages and their data content to ensure they are all valid so your assumption that it is looking for other data is no doubt right, but it may be as simple is looking for the engine speed message/data as oil pressure without engine speed is invalid. (for example) though they may also be looking for the "hello PCM present! " message as well.

[matthud]

If I send the message once, the needle sets. If I dont send the message again within a short period ~5 seconds, it pegs again. So if I send coolant temp = 190 every 5 seconds, the needle will stay at 190 for ever.

[LSX378]

If I send the message once, the needle sets. If I dont send the message again within a short period ~5 seconds, it pegs again. So if I send coolant temp = 190 every 5 seconds, the needle will stay at 190 for ever.

Well there is your answer. GM HS CAN messages typically repeat at 20 to 500 times a second depending on their purpose so it looks like you need better than 1 per 5 sec. And probably 1 per sec.

[matthud]

But this is not CAN, it doesnt have nearly the same bandwidth. That many messages just for the gauges seems like a lot of network traffic.

[LSX378]

But this is not CAN, it doesnt have nearly the same bandwidth. That many messages just for the gauges seems like a lot of network traffic.

Yes you are dead right there though it would be reasonable to expect a multiple (down) based on bit rate.

And clearly if no messages in 5 sec then back to sleep, so why not try 1 message per sec?

Not enough for speedo or tacho but ok for temp/oil/fuel.

What interface hardware are you using?

[matthud]

Yes you are dead right there though it would be reasonable to expect a multiple (down) based on bit rate.

And clearly if no messages in 5 sec then back to sleep, so why not try 1 message per sec?

Not enough for speedo or tacho but ok for temp/oil/fuel.

What interface hardware are you using?

elm322

[LSX378]

So your interface is working well and you have the right messages and can wake the gauges up .. whats the problem?

[matthud]

Well, now I need to know how to get rid of the "Reduced Engine Power" message that the DIC is displaying.

[LSX378]

Well, now I need to know how to get rid of the "Reduced Engine Power" message that the DIC is displaying.

Well that message could come from a number of sources. For example lack of ABS OK or PCM OK messages could enable that message.

[matthud]

When you say OK messages, do you mean the State of Health messages?

[LSX378]

When you say OK messages, do you mean the State of Health messages?

Messages. Just like the message you constructed for oil/water/fuel. If an expected message doesnt arrive or the content is invalid then there is a fault.

[Bluecat]

Sure be great if I could talk you into sharing the info you have. I'm putting a LS engine into a Dakota and was planning on running the Dodge dash with the GM pcm. Taking a C-Stamp and writing a program to read GM and spit out Chrysler shouldn't be a big deal. I was just dreading having to find the info on the data formats or having to monitor the data line on stock vehicles and reverese engineer them. I already found some info on both the Chrysler physical and data implimentation oddly enough. So If you'd share your info on the GM side I'd have a hell of a running start when I actually begin my swap and have to start working on the converter box.

Oh and on your project, thats just the way it is. The cluster is alway expecting a stready stream of updates. I'm suprised it waits as long a 5 seconds to default back. So I doubt there will be a command to make them hold. And I'm not sure why you would want them to. Gauges that arn't real time, well, arn't gauges. Just like on a stock vehicle while you are flashing the pcm the comms stop. The gauges all default until programming is complete and the pcm begins normal traffic again.

[vettedan]

Hey matthud, I hate to step on your tread, could you shed any light on my Serial data problem below:
Thanks,

I just finish installing a 2000 F-Body LS1/ 4L60E into a 1984 Vette. I also swap in a 2000 C5 Vette dash /cluster so I would have a turnkey display. Everything is working (speedo, tach, engine temp, voltage) but some of the serial data like the fuel level & oil pressure is not. I have a 2002 F-Body PCM . The pin out between the F-Body & 2002 Corvette PCMs look the same except the corvette have extra options. I tried adding the corresponding pins for the fuel & oil pressure gauge but the serial data is still not getting information to the gauges. All the other serial data is being display on the C5 cluster: tire pressure, coolant temp, oil temperature, etc.
I figured the 2002 Camaro PCM would be identical to the 2002 Corvette , but maybe it’s not or is there somewhere on the HP tuner S/W I need to add these functions. I look around but couldn't find anything. The fuel gauge should at least work? Transducer Ground issue?
Does anyone have any ideas?
Thanks,
Dan

[1998Ws6]

I would try to enable the oil pressure equipped in the options matrix if hptuners supports this function.

Ryan

[04colyZQ8]

Trying to emualte speedo, tach, temp, and gas gauge for the 5 second startup on a colorado, wiht GM class 2 data. Can you help? How do you send the sommands, and waht are they? This is for testing clusters wiht custom lights. What program do I need?

[WDZaphod]

AFAIK Fuel Level and Oil pressure is NOT on Class2" it goes direktly wired to the IPC. Take a look at the C5 IPC Pinout, there you will find the right Pins :-)