you should be able to use any of these that have the same ALDL Data stream as the Fiero... A104 or whatever it is...

So do all 86 and later Fieros have this plug in the harness? is it only in 86 cars? if only in 86 was it in all cars of that year? Does anyone have a pic of this plug in their harness?

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BLACKKER 1988 choptop v8

http://www.foxvalleyfieros.webs.com/

N.I.F.E. member #461
http://www.fierofocus.com/

This is getting very interesting.

Yes, it is. I want to know more.

Only because the Fiero's diagnostic data stream is the same as that of another ECM doesn't mean the rally data stream is also the same!

While the C3 ECMs (like the Fiero ECMs) share the basic communication format, the frames sent are different and contain different data depending on the modes supported.

The Fiero V6 ECMs supports two/three communication modes:

- limp-home-mode aka backup-mode aka 3.9K mode. This mode is for forcing the ECM into limp home mode. The data transmitted on the ALDL line is not useful. This mode is entered by a 3.9K resistor across the A&B pins.
- diagnostic mode aka ALDL-mode. This is the common diagnostic mode used by all scantools on the Fiero. The ECM switches to diagnostic mode if a 10K resistor is found on the A&B pins of the ALDL connector. The data is only useful for diagnostics. No MPG/mileage/rally data is contained in the data stream.
- open mode aka road mode. Nothing is connected to the A&B pins of the ALDL connector. The 85/86 ECM does not transmit anything in this mode. Only the 87/88 V6 ECM transmits MPG information. The frame is only 5 bytes, so the data is updated about 5 times as often compared to the slow diagnostic data rate.

There are some fixed values in the rally data stream that may be vehicle type or engine type or calibration values. Only GM knows what they're for.
So the road mode data stream may or may not work with another vehicle's DIC.

So it's better to say "it might work" than "it should work".

[This message has been edited by fieroluke (edited 09-30-2010).]

I dont think anyone is saying it should work, but as you said there are headers associated with the data streams so it could be very possible that the design was modular enough to work cross platform if the technology was recycled.

Luke, it sounds like you are saying that hooking the rally gauges to the adl port may not work, that could very well be true, but they are saying that the harness they have found that seems to be purpose built hanging under the pass glovebox area may tap into a useable data stream that could possibly be used for an 80s gm simple ralley computor. I know Im excited about this prospect, hope it can be done......

Wow, Something cool about Fiero's that I knew NOTHING about! Write down the date! Thought I knew it all. You know... I don't see it being difficult to make a form of reproduction.

Parallax Basic Stamps easily talk serial, and can compute as well as control displays, have button inputs and all sorts of programming flexibility... Just sayin'. <$80, and a lot of patience, you could make it work.

So if what is being said is true, the 86 computer doesn't have this capability. But, the 87 does...I have an extra ecm for an 87, I may just swap it out and wire this thing up temp, just to see if it works.....- Jason

quote darkhorizon: I dont think anyone is saying it should work

...well, Kurt said:

quote KurtAKX: you should be able to use any of these that have the same ALDL Data stream as the Fiero..

All I was trying to say was it *might* work, and that "it should work" is a bit optimistic.

quote as you said there are headers associated with the data streams so it could be very possible that the design was modular enough to work cross platform

True. It's definitely worth a try. But the configuration consists of two bytes of unknown purpose. Those two bytes would have been sufficient to calculate MPG cross platform, but I doubt it would also contain fuel tank level calibration. So the MPG display might even work, but the range wont.

The fuel level guesstimator (calling it fuel gauge would not do it justice) GM blessed our cars with is far from accurate enough to calculate range information that is even remotely reliable. So any trip computer would have to have a table converting fuel sender resistance values to remaining gallons, which would be specific to a certain fuel tank shape and vehicle. But the closer the tank comes to empty, the more accurate the calculation will be, with 0 for an empty tank probably being the only accurate prediction ;-)

If anyone is interested, I have build a MPG gauge calculating current mileage to plug into that connector. It displays current MPG (and outside temp), but not range (for the above reasons). The reason I haven't published it is the price of the display (one is required, two are nicer) is $20 (check digikey.com, part name SLO2016). With $40 for the displays alone plus processor, supply and circuit board, the total quickly comes to the $60-$70 range (minus $20 if only one display is used). I think few would pay that, so for now there is only my prototype. It goes into the unused slot above the tach, BTW. No unsightly boxes to install anywhere.



PMD had the same mounting location dilemma obviously, or else they would have found a better solution than to integrate a trip computer in the passenger side map strap...

I have a few spare circuit boards and can supply a few programmed CPUs at cost if anyone is inclined to build one. Let me know.

Oh, before anyone yells MPGuino or basic stamp (darn, too late...), don't bother with (standard, i.e. cheap) LCD multiplex displays in a car. They turn black when the interior is over 100F and when it's below freezing outside, the display literally slows down to a freeze as well. Fine for showing off at a car show, but only useable if you operate your Fiero in a climate chamber.

It seems to me that the location for the display is not really practical. It would be hard to read any data from the driver's position and pushing any buttons would be a PITA too. I guess calling it a Rally Computer is appropriate because you would need a co-pilot to read the info to you.

A number of years ago I did a 3800 Series 2 SC and 4T60-E swap into a 1988 Buick Reatta that had the CRT. I used a 1994-95 OBD1 (aka: OBD 1.5) PCM. I could not get the 94-95 PCM to communicate with the BCM or CRT in that Reatta.

I got my hands on some data stream disassemblies that showed the message scheduling and how the data being sent out was structured. From the limited amount of time I put into researching these disassemblies, I discovered that GM changed the message scheduling / data structure being sent out on the ALDL serial data line pretty much every year to every other year and also changed it for different vehicle car lines. (If anyone wants copies of these datastream disassemblies, shoot me an email at sp1@gmtuners.com and I'll happily send them to you).

Basically what this boils down to is you can't take a Driver Information Center / Trip Computer out of a Buick Reatta or Ponitac Grand Prix and get it to work in the Fiero using the stock Fiero ECM. The data message structure is different. Back in the day when I was still messing with Chevy TPI V8 stuff I couldn't get the digital dash out of a Cutlass Supreme International to work with a TPI computer even using the same ECM (1227727). The tach on the digital dash got RPM info straight off the serial data line but the V8 programming ($8D code mask) did not have the correct ALDL data message structure to work with the cluster out of the Cutlass.

Another way to look at this is to see how a scanning program like WinALDL works. If you configure WinALDL to scan a Fiero 2.8 (1227170 ECM), you will notice it may be able to communicate with another 1986-88 GM car ECM, but the data won't be displayed correctly (invalid readings). This would tell you right there the data structure is mismatched.

Now I'm sure if someone wants to spend the time hacking deep into the programming of an ECM and has an understanding of what they are doing, they MIGHT be able to change the data messaging structure so it would be compatible with hardware from another GM car. But I'm sure you are NOT going to be able to just pull a DIC or Trip Computer from another GM car and plug it into your Fiero and make it work unless you are running the same ECM and programming as the car you got the DIC/Trip Computer out of.

-ryan

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7+ years on this same swap -- NO engine or transmission failures...

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

quote Originally posted by Darth Fiero: A number of years ago I did a 3800 Series 2 SC and 4T60-E swap into a 1988 Buick Reatta that had the CRT. I used a 1994-95 OBD1 (aka: OBD 1.5) PCM. I could not get the 94-95 PCM to communicate with the BCM or CRT in that Reatta. I got my hands on some data stream disassemblies that showed the message scheduling and how the data being sent out was structured. From the limited amount of time I put into researching these disassemblies, I discovered that GM changed the message scheduling / data structure being sent out on the ALDL serial data line pretty much every year to every other year and also changed it for different vehicle car lines. (If anyone wants copies of these datastream disassemblies, shoot me an email at sp1@gmtuners.com and I'll happily send them to you). Basically what this boils down to is you can't take a Driver Information Center / Trip Computer out of a Buick Reatta or Ponitac Grand Prix and get it to work in the Fiero using the stock Fiero ECM. The data message structure is different. Back in the day when I was still messing with Chevy TPI V8 stuff I couldn't get the digital dash out of a Cutlass Supreme International to work with a TPI computer even using the same ECM (1227727). The tach on the digital dash got RPM info straight off the serial data line but the V8 programming ($8D code mask) did not have the correct ALDL data message structure to work with the cluster out of the Cutlass. Another way to look at this is to see how a scanning program like WinALDL works. If you configure WinALDL to scan a Fiero 2.8 (1227170 ECM), you will notice it may be able to communicate with another 1986-88 GM car ECM, but the data won't be displayed correctly (invalid readings). This would tell you right there the data structure is mismatched. Now I'm sure if someone wants to spend the time hacking deep into the programming of an ECM and has an understanding of what they are doing, they MIGHT be able to change the data messaging structure so it would be compatible with hardware from another GM car. But I'm sure you are NOT going to be able to just pull a DIC or Trip Computer from another GM car and plug it into your Fiero and make it work unless you are running the same ECM and programming as the car you got the DIC/Trip Computer out of. -ryan

Darn.....

quote Originally posted by av8fiero: So do all 86 and later Fieros have this plug in the harness? is it only in 86 cars? if only in 86 was it in all cars of that year? Does anyone have a pic of this plug in their harness?

Anyone know the answer to this? Really cool topic!

I don't think more than a few cars had this harness built into them. GM surely got preproduction samples from whoever made the wiring harnesses for them. We always had to provide samples to GM as well at my old job. I know GM was sloppy with the handling 10 years ago, so I don't think they were any better 20 years ago.

Maybe one of those samples accidentally got put into this car. Maybe the car was a test car that they forgot to pull from production. We'll probably never know.

Anyway, as far as the harness with the extra plug is concerned, in the words of young Indiana Jones: "This belongs in a museum". Along with a power steering unit and the flux capacitor which was rumoured for the 89 model year.

Don't they still make aftermarket trip computers with the magnet that gets taped to the driveshaft?

Maybe someone should approach Tom (TBSB9595). Since he custom builds digital dashes over here https://www.fiero.nl/forum/Forum4/HTML/034606.html maybe he could build something? I'm sure that the cost may be high, but it would be cool and his quality looks great...

I took my own advice and post over there.
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-Brian

My 87 GT Poly Suspension Upgrade (all pics) thread
Removing the roof panel

[This message has been edited by MulletproofMonk (edited 10-01-2010).]

When I spoke to an engineer on the project a few years ago he stated that the computer was to be a true really computer and not a MPG/trip computer as in most GM cars. He said that many if not all 87 ecm's had the needed programing in them. That's something you electronic guys might be able to comment on. He said the computers were going to be provided by an outside company that was into racing computer systems. He could not remember the name of the company of the person he worked with but claimed he had that information in his files. He has never gotten back to me with that yet. He said that cost was only a minor issue in why it never was put into production. The reason he remembers as being the largest concern was that they were also beginning work on airbags for the Fiero and both were designed for the same space. Since airbags were being mandated the choice was to drop the computer and develop them. He couldn't remember much about what they had to do on GMs part to make the system work but thought that all the computing was done by the provided system. It was his feeling that all they had to provide was a couple of data stream taps. He thought that it would be something that any modern computer could handle with the right program. He thought that the biggest problem was keeping the systems clock accurate since time was a major factor in the calculations the computer was doing.

I'll doing more checking and see if I can come up with anything else.

This is all beginning to sould like and project to be added to my ever growing of list to things to consider as update additions to my '86 GT.

Thanks for sharing.

I cannot find any documented data that the V6 puts out chatter when A-B are not shorted/10K'. So I don't see how this would work under normal circumstances. The fact that the serial is pulled from Pin E means its not for 87-88 4 cyl cars (they put out data via aldl pin M) and that it reads 160 baud, which is extremely slow. 84-86 4 cyl's do put out chatter, but it is missing a few critical values that any MPG computer would need, most notably BPW. I wonder if there is an undocumented feature that the 86-88 V6 ECM's have where they can put out ALDL Chatter when A-B are not shorted or 10k...

quote Originally posted by av8fiero: So do all 86 and later Fieros have this plug in the harness? is it only in 86 cars? if only in 86 was it in all cars of that year? Does anyone have a pic of this plug in their harness?

So does anyone know the answer to this? I'd really like to know. I'd love to see a pic of this plug on someone's car. I'm also curious if it's there on mine.

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BLACKKER 1988 choptop v8

http://www.foxvalleyfieros.webs.com/

N.I.F.E. member #461
http://www.fierofocus.com/

I have a random unused 8pin plug that i discovered installing a new head unit. Its in my 88 coupe.

I had a chance to talk to some people that were around the rally computer option over the weekend. In the early stages of the project, the serial line chatter and speed interfered with the rally computer which was engineered more along the lines of home computer. There was a voltage converter to run the computer at 12V instead of what the rally computer was initially designed at. The system worked great in testing, but did not when tested in actual use. There was a redesign of the ECM to correct this, but being a change in the ECM, the new design had to be recertified. All this created delays and increased cost. By the time the defects were sorted out, and by later in 86 it was to late. The option would have been offered at over $500 retail and marketing was concerned about who would actually pay for the limited use option. Remember, we are dealing with the general public. Plus future product development would have not allowed enough packaging room to place the rally computer in the center part of the dash. By 86 engineers were working towards a new dash design that had the passenger side of the dash occupied with a glove box, automatic temperature control HVAC and the pending future of the airbags.

My friends are seeing if they can find the name of the supplier which they recall as being in California. It would be neat to see if any exist. You just never know.

Thanks Rick (ARKaiser) for sharing your information that you have. If I hear anymore, I will send it along to you. It sounds like what you were told is in lines with what I was told.

Fred

quote Originally posted by RAREW66: So far there is not definate answer to this. I have two 86 harnesses that came off cars built in June and July that do not have the 8 pin connector. The PDM sheets I provided have the location of the connector. Fred

My car was built in October of 85, so it must only be the early 86s.

Matt

quote I cannot find any documented data that the V6 puts out chatter when A-B are not shorted/10K'. So I don't see how this would work under normal circumstances. The fact that the serial is pulled from Pin E means its not for 87-88 4 cyl cars (they put out data via aldl pin M) and that it reads 160 baud, which is extremely slow. 84-86 4 cyl's do put out chatter, but it is missing a few critical values that any MPG computer would need, most notably BPW. I wonder if there is an undocumented feature that the 86-88 V6 ECM's have where they can put out ALDL Chatter when A-B are not shorted or 10k...

Well, documented or not (it is documented in the source code, and the data is called "rallye frame"), the 87/88 V6 ECM DOES output data on pin E if A-B are open. Believe it or not.

And yes, it's 160 baud, but the frame is only 5 bytes, so it's about 5 times the update rate of the 25 byte diagnostic mode (10k mode).

No, the rallye data stream does not include BPW either, because the update rate is still too slow to accumulate the BPW in an external computer, BPW is updated a lot more often (every tick or every other tick if I remember correctly). Instead, the ECM takes care of integrating (adding up) the time the injectors were open. It does not take into account the cold start valve (not ECM controlled), and it does not take into account the fuel pressure variations caused by vacuum on the pressure regulator either, so it is not absolutely accurate. There is also a bug in the ECM code, which causes inaccuracies in fuel cutoff mode (DFCO).

Still, the value is only a quart off max. in my car after filling up 30-35 Liters. Not bad at all. At today's fuel prices here, the momentary fuel consumption is my most valuable reading, it really helps to know when the engine is guzzling and when it's not.

[This message has been edited by fieroluke (edited 10-05-2010).]

I had this connecter in my 1986 SE and was like What the?!?! everytime i saw it! I didnt know where it went to and it was the same shape as the radio harness... My 1986 gt does not have it... My GT doesnt have the factory sub wiring too. I wonder if thats related?

i just checked both of my 86 gts neither of them had what would appear to be an extra wire so if some one can post a pick of what this connector looks like that would be great. also i just looked under my dash do i actually have to take my dash apart to see this plug?

I have both a 86 and 87 car, if I can see what I'm looking for I'll check it out a.s.a.p. on my cars.

Check out this Fiero on ebay. In the right up, it claims to have a DIC & trip mileage computer. There are shots of the interior, hard to make out but it doesn't look like the regular "glove box" area of a fiero, The window sticker doesn't list it either but...could it be? What do you think?

http://cgi.ebay.com/ebaymot...&hash=item230af3c0dc

Mark

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86 SE V6 4 speed
86 SE V6 Auto
2008 G6 GT "Street" Coupe

It's definitely in mint shape, but it's just a plain old SE, as far as I can tell. "Glove box"/map holder looks normal to me. He also claims it has power steering, sooo... yeah.

Nice find, regardless!

[This message has been edited by Valkyrie (edited 10-17-2010).]

quote Originally posted by Valkyrie: It's definitely in mint shape, but it's just a plain old SE, as far as I can tell. "Glove box"/map holder looks normal to me. He also claims it has power steering, sooo... yeah. Nice find, regardless!

Went back to the seller with questions. The mileage / trip computer could mean the resettable trip odometer heh heh.

Nice car for a swap, a potential little red bullet sleeper.

Mark

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86 SE V6 4 speed
86 SE V6 Auto
2008 G6 GT "Street" Coupe

quote Originally posted by Valkyrie: It's definitely in mint shape, but it's just a plain old SE, as far as I can tell. "Glove box"/map holder looks normal to me. He also claims it has power steering, sooo... yeah. Nice find, regardless!

Yeah, a LOT of people did this with the Fiero... I guess thinking it was going to be a very valuable collector car in the future. I don't doubt our cars will have some value in the future, but not to the level that person was probably expecting.

That's a car that, right now... would make a perfec daily driver / commuter car. I can't think of anything more cool that I'd want to be driving around in as my daily driver if fuel economy and agility were important.

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Todd,
2008 Jeep Patriot Limited 4x2
2002 Ford Explorer Sport 2dr 4x2
2002 Ford Crown Victoria LX
1987 Pontiac Fiero SE / V6
1973 Volkswagen Type-2 Transporter

quote Originally posted by Valkyrie: It's definitely in mint shape, but it's just a plain old SE, as far as I can tell. "Glove box"/map holder looks normal to me. He also claims it has power steering, sooo... yeah. Nice find, regardless!

That's not an SE. No power options, no stripes on the seat, etc. No SE on the Sail Panels either.

[This message has been edited by TONY_C (edited 10-17-2010).]

It also really makes you wonder what other goodies are hiding in peoples garages out there. I mean, where are all the other Enterras? Or perhaps even the few 88's that may or may not have escaped the factory with some sort of power steering add on?

It's almost like finding rare fish at the bottom of the ocean. Fortunately, our cars aren't so terrifying.

quote That's not an SE. No power options, no stripes on the seat, etc. No SE on the Sail Panels either.

Doh! I just looked at the sellers description and went off that, didn't even think to look for that! Good catch!

[This message has been edited by Valkyrie (edited 10-17-2010).]

I want one, I want one!

Wonder if there's a way to work it into a heads-up type display with the function buttons in a remote location (somewhere in the center)?

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* 1984 Black Fiero SE (1995-1998) blown tranny - rest her soul
* 1988 Black Fiero Formula (2001-2004) Was to be a 3800SC, badly rusted rear frame.
* 1988 White Fiero GT (2009 - Present) This one's a keeper!

quote Originally posted by fieroluke: and it does not take into account the fuel pressure variations caused by vacuum on the pressure regulator either

The vacuum referenced fuel pressure regulator maintains a consistent pressure drop across the injectors (from inlet to outlet) which actually helps the ECM because it keeps the injectors flowing the same amount of fuel no matter what the pressure in the manifold is. Without it, a rock-steady fuel pressure would result in different amounts of pressure drop across the injectors which would vary as manifold pressure changed.

For example, let's say your fuel pressure is 47 with no vacuum (or boost) present in the intake manifold or acting on the fuel pressure regulator. Now when your manifold pressure is 15 in/hg of vacuum (or the ~ equiv of -7 psi pressure), this amount of vacuum acts on the FPR and lowers the fuel pressure to about 40 psi. Since there is now about 7psi of less pressure in the intake manifold, the pressure differential between the fuel rail and intake manifold is still 47 psi.

-ryan

Ah, clever. Thanks for the explanation, Ryan!

But in any case, I've compared the accumulated fuel values the ECM outputs in "rally mode" on my three Fieros when I tried to calibrate my MPG-meter, and there's quite a bit of variation between the three of them. I have then calibrated the unit for my daily driver, and still, the total fuel measured by the unit and the total fuel displayed by the gas meter at the station (yup, always the same pump!) are still off by about a quart in either direction. Sometimes high, other times low. Maybe I could get the reading more tightly tolerated if I put more effort into it, but I think it's accurate enough as it is. It's more than accurate enough for current MPG, which fluctuates anyway under load changes.

Regarding GM, I don't see how they could have had a really accurate accumulated fuel reading without some means of calibration. But maybe they had a provision for that. I guess we'll never know...

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Visit my website: www.fieros.de for lots of technical and other Fiero related information
Maroon 87 GT daily driver with Firebird Body Control Module, Power Window Controllers and Dash mounted Scantool/Trip Computer