I just got a Bluetooth scan tool, mostly so I could diagnose an extremely intermittent P0706 code, but to my disappointment, it appears that the sensor inputs used by the PCM to generate that code - namely the "transmission range sensor" - isn't one of the generic sensors.

So yeah, either I suck at googling or this information just isn't easy to find it the sea of garbage.

 

https://charm.li/Saturn/1999/SL2%20L...8%20DTC%20%29/

 

Yes, I know about that site. If you look at the transmission codes, e.g. P0706, you'll see something called a "Scan tool" mentioned. This was probably a device that already had the Saturn specific PIDs programmed in. E.g. it might have had a display that showed what position the PCM thinks the "transaxle selector" (PRND32) was in, which works by requesting the sensor data and interpreting it accordingly.

https://en.m.wikipedia.org/wiki/OBD-II_PIDs#Service_02

I'm definitely getting ahead of myself, having spent less than an hour learning about how OBD-II works, but I find it extremely unlikely GM/Saturn designed an entirely new system for transmission related diagnostics. There's gotta be a PID I can input into the app to be able to emulate the official (or whatever "Scan tool" means) tool's functionality and that's what I'm asking about.

 

You don't know what a scan tool is? Take your car to a shop.

 

Kinda brutal, man.

People come here to learn.

Someone trying to address OBD2 codes based on to-date little research, zero experience, and no guidance is someone who wants to learn.

Wrong terminology used? Par for the course for a noob at anything.

Spread your wisdom......

 

If you were actually capable of reading or writing English, you would understand from context that my reference to the quoted "Scan tool" is whatever proprietary device is being mentioned in the charm.li troubleshooting diagrams.


Interesting start here.

 

I get the impression y'all think I'm talking about the error codes. For example, the error code P0133, which is set when the bank 1 oxygen sensor isn't switching from rich to lean or lean to rich fast enough. I'm not. I'm talking about the "PIDs" (parameter ids) you can enter in scanner apps to get the output of specific sensors.

For example, engine coolant temperature is PID #5, which returns a single byte (0-255). To compute the actual temperature, the app would be subtract 40 to get Celsius then if necessary convert that number (-40-215 °C) to °F.


I'm asking about this because I don't see any transmission PIDs amongst the hundreds that come preprogrammed into the app, but I'm 99.999% sure someone knows how to configure the app to be able to see, e.g. the value of the "transmission range sensor", which is used by the PCM to calculate which of P, R, N, D, 3, or 2 is selected.

By the way the specific Android app I've been using is called "Car Scanner ELM OBD2" (com.ovz.carscanner).

 

I'm sorry that I can't help you with that, but if you ask around a few shops if they have an older "tech" who might be familiar with Saturns, maybe they could help. I don't know if any particular scanners on the market have what you're looking for since Saturn has become extinct.

 

The manager at my local AutoZone wanted to buy my 1999 SL2 and says he's owned 4 before but the fact that he was totally unaware of the F5 issue makes me doubt he would know something far more esoteric like this. Still, I suppose it wouldn't hurt to try.

Anyway I've been reading various posts around the Internet this morning and I found a thread with a partial list of PIDs for a 2008 Colorado, which includes parameters such as "current gear" and "transmission range", which are probably going to match the Saturn PIDs, since like I said, it would be stupid and pointless for GM to define multiple sets of PIDs.

I'm beginning to think it was intended, back in the 1990s, that manufacturers would keep their PIDs secret and license them out to scan tool manufacturers at obscene markups. It's only been in the past couple of years that the cheap Bluetooth scanners have made it possible for nerds like me to have an interest in reverse engineering this stuff. The combination of the relative uselessness of the nonstandard parameters, Saturn being extinct for 15 years now, and the death of saturnfans.com, which afaik was by far the largest source of info on Saturns, means it's possible what I'm looking for simply doesn't exist yet.

 

Supposedly there was one guy. One. Who was able to crack the communications mask on the PCM and I believe read exactly what you're looking for. The AH posted screens showing such data. They also never shared a ****ing thing with anyone.

Saturn was quite standalone when it came to design. Very little overlap in parts in the beginning with the s series cars and the rest of GM. This is evidenced by looking at the fitment of pretty much any Saturn part on an s series or l series car. Ion and cobalt were much closer. But in the beginning it was essentially a one-off design.

For whatever reason, GM locked down the s series PCMs. That's why nobody knows what is stored where. No one can get in to map it.

For the record, my post was not directed towards you. It was directed at the person who posted after you. I didn't open the charm thing but Saturn text used GM tech 2 devices at the dealership. Much more broadly functional than what's available today to support a Saturn in troubleshooting and other functions.

I wonder if you used a tech 2 if it would access all of the PIDs, thereby providing you with a map of all of them.... I've been wanting to buy one with an OBD1 adapter for my '95 coupe but I just haven't pulled the trigger.