Affordable full scan tool for the V6 Fieros (Page 3/4)
Romsk JUN 05, 06:37 AM
Cartercarb,
What does my GUI do that makes it something you seek rather than use Tuner pro?

Reinhart,
I don't know much about the parallel port cables. I think they are very similar to the serial port cables except they put the data on one of the data pins (possibly D0).
There are small Adapters that you can plug in (or hard wire) to a serial cable to convert it to USB. When I converted my first serial cable I made, I just wired a Parallax Serial/USB adapter to it. There are many sources of these. The Parallax one is:
Parallax USB-Serial Adapter

[This message has been edited by Romsk (edited 06-05-2025).]

Romsk JUN 05, 07:03 AM
Reinhart,

My GUI originally was designed to work with the common Serial Cables that most of us built from the web years ago. In fact, the code is still in the GUI for them but they convert ALDL 1s and 0s to ASCII characters (I forget which) and mine converts to ASCII characters '1' and '0' (which has a more logical sense). I could re-enable that code so my GUI will work with Serial Cables (for PCs with serial ports) or with a USB Adapter attached (for PCs with USB ports)... but here's the rub: Serial cables won't understand the commands my GUI sends to the Adapter... those old cables work one way (read only), they are not interactive. So they would sort of work, but you would have to set the ALDL modes by manually applying various resistors between GND and the Mode pin on the Fiero's ALDL Connector. And because the serial cable does not interact with my GUI, all sorts of errors would show up. It would sort of work, but you would get a lot of "flack" from the GUI reporting comms errors with the serial cable (that simply won't respond to commands).

This is why my cable evolved to having a tiny microcontroller inside it. I can change the code in it to continue to evolve. For example, when I start to support 1988 Fiero IL4 ECMs, my Adapter has to switch to 8192 ALDL baud AND be commanded to request each ALDL Frame (very interactive)... because it is an intelligent microcontroller inside, I will be able to do that with small design changes to my Adapter (connect pin M to pin E, and some microcontroller code changes), the GUI will need more significant changes for that.

Paul

[This message has been edited by Romsk (edited 06-05-2025).]

Dennis LaGrua JUN 05, 07:08 PM
FYI very few scan tools will read the transitional OBD 1.5 codes. Cadillac 4,5l/4.9L and later 3.4DOHC swaps have these ECM.s The one that will scan these ECM are some versions of AutoXray, Actron and Snap On. There also seem to be few scanner that can interface with the DIS 4 cylinder Fiero ECM's.

------------------
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Romsk JUN 06, 02:32 PM
What is DIS?
Kitskaboodle JUN 06, 02:39 PM
I don’t have a 4 cylinder Fiero but I will assume it’s the removal of the distributor and in its place is coil packs and a crank trigger setup. But I could be wrong… Kit

[This message has been edited by Kitskaboodle (edited 06-06-2025).]

1985 Fiero GT JUN 06, 03:06 PM

quote
Originally posted by Romsk:

What is DIS?



Distributor-less ignition system
richard in nc JUN 06, 07:12 PM

quote
Originally posted by Dennis LaGrua:

FYI very few scan tools will read the transitional OBD 1.5 codes. Cadillac 4,5l/4.9L and later 3.4DOHC swaps have these ECM.s The one that will scan these ECM are some versions of AutoXray, Actron and Snap On. There also seem to be few scanner that can interface with the DIS 4 cylinder Fiero ECM's.



my scan tool works with my 1987 2.5.it shows the info.it won't clear the codes though.
Romsk JUN 08, 05:54 AM
1895 Fiero GT,

Got it: Distributor-less Ignition System (DIS). Thanks.

I have never seen a Fiero IL4 engine in person. Mainly various photos out of any real context.

Do "ALL" of the stock Fiero IL4 engines use DIS?

Reading part of the Fiero 1986 Service Manual, there are three 2.5L IL4 engines used by Pontiac at the time:

Engine Code, Regular Production Option, Cylinders, Carburetion, Displacement, DIS

R LR8 IL4 TBI 2.5L Yes/No?
U L68 IL4 TBI 2.5L Yes/No?
2 LQ9 IL4 TBI 2.5L Yes/No?

My GUI now has a VIN Lookup feature for Fieros based on what I read. If DIS is a factor, I will add that too.

Since I am expanding my GUI to support the IL4 engines, knowing these details helps me.

Paul

[This message has been edited by Romsk (edited 06-08-2025).]

Romsk JUN 08, 06:08 AM
Richard,

None of Fiero ECMs that use 160 baud can have their Error Codes (ECs) cleared via the ALDL because the protocol does not receive commands, it only spits out data. The only way to clear ECs in those ECMs is to remove 12V power to the ECM for at least 1 minute. Removing the ECM Fuse will not do this, it has to be power to the ECM that comes from the ECM Fusable Link.

There are two normal ways to do this:
1. Disconnect the Negative side of the Battery for 1 minute (radio settings will be lost).
2. If there is a single wire connector on the ECM Fusable Link (near the battery) disconnect it for 1 minute (radio settings not effected).

The 1988 IL4 ECMs use 8192 baud and I am told they do receive commands. But I do not know if there is a command to erase ECs on that ECM.
I am expanding my GUI to support 4 cylinder Fieros, but I haven't gotten to that ECM yet, so it is a big unknown to me.

You have a 1987 IL4 Fiero, it's 160 baud, no command to clear ECs.

Paul

[This message has been edited by Romsk (edited 06-08-2025).]

Patrick JUN 08, 03:44 PM

quote
Originally posted by Romsk:

Do "ALL" of the stock Fiero IL4 engines use DIS?



"IL4" - In Line Four ?

No. '84-'86 have a distributor. '87-'88 are DIS.