1997 F-Body ECM

[Tom H]

I was told that there was not really a solution for the 96/7 vehicles hence was directed to here as the closest kind of "DIY" tuning solution.

Just like the P01/P59 PCMs, there was not really any work done for reverse engineering completed or people helping out until there was an option available to read/write.

Id be happy to help get the kernels into a easy to use application, or even possibly into something like LSDroid which is also a free based program.

As this is part of the "tools" topic, we should move the discussion there http://www.gearhead-efi.com/Fuel-Inj...7-F-Body-Tools

I have a solution for read & program of the 96/7 LT1 PCMs. This all is separate from the bootstrap discussion (resurrection of the bricked).

I have a good deal of the reverse engineering done with a little help from my friends here.

My software skills are not quite up to your level. I don't have kernels. Just a few c++ classes that I stitch together to upload/download code to the PCM. For the actual programming routines that run on the 'HC11s, Kur4o provided them and I used them without (or with few) modifications. If you would like to make up a tool for these PCMs I will try to support you where I can.

-Tom

[kur4o]

Hi Tom,

Did you managed to reverse the hardware side of ignition control. I am only interested in the signal that pcm sends to ignition control module and what type of it is. Usually there is a dwell timing that goes to ICM. Does the pcm supplies voltage or just ground the icm pin, while grounded the coil charges and once the ground is removed the coil fires. I am just speculating. I think this was covered in other threads but can`t find it.

Thanks

[Tom H]

Hi Tom,

Did you managed to reverse the hardware side of ignition control. I am only interested in the signal that pcm sends to ignition control module and what type of it is. Usually there is a dwell timing that goes to ICM. Does the pcm supplies voltage or just ground the icm pin, while grounded the coil charges and once the ground is removed the coil fires. I am just speculating. I think this was covered in other threads but can`t find it.

Thanks

Hi,

I will give you all that I have, some hope it will be what you need.

The signal we are speaking about: ignition control is generated by the ESide and connects out through Black or C2 pin 5. The ignition control is both an output and an input (I expect the earlier PCMs are the same). The output is pulled high resistively and an NPN transistor is used bring the signal low. The output is monitored by a mystery chip marked 27474. I think this is a small semi-custom chip like a pal or something. Probably not too much in it.
Your question I think goes to the output type but once dwell comes into it, that is all TPU. Still banging my head on that chip. Some figured out but not all.

Here is the schematic for the bit you are concerned about.

Ignition.jpg

If I didn't answer your question...please ask again

-Tom

[kur4o]

I am mostly interested in the interaction between pcm and ICM. Type of driver and how that interacts with dwell time. I need to reread the coil thread.

Thanks for the schematics, looks really interesting. On engine cranking service manual specify 1-4V AC voltage output from pcm to ICM. Not sure how that correlates with dwell time. I guess some scoping will reveal more.

[kur4o]

I went through 55 page thread and here is some scope chart of dwell signal from 94-95lt1.
Might give you some insight to better correlate it with hardware side.
http://www.gearhead-efi.com/Fuel-Inj...=180#post67834

http://www.gearhead-efi.com/Fuel-Inj...8&d=1510370313

[Tom H]

HI,
The TPU asserts and de-asserts the ignition control output. It also monitors the ignition control, verifying that there is no external short (it may also look at timing to ensure there isn't too much loading).

I don't have all the answers here... yet but the pins involved on the TPU are 7, 8 and 9. Pin 7 is the monitor. I believe 8 and 9 control the output with one being "limp mode" and the other normally used to fire the coil. I don't have an ICM to check the function however it looks to me like it is just a switch. It is external to the PCM for maintenance and thermal reasons. Perhaps you can answer- is the ICM just a switch with certain limiting built in? This is what I expect.

I need to read the thread before I get further into the ignition control of the TPU.

-Tom

[kur4o]

I cracked open 2 ICM one original gm one and some chinese knock off.
Gm looked like knock module inside, had some fat transistor soldered to back steel plate to enhance cooling, and some small factor custom chip.
Chinese knock off was dead already with no runtime. There was some transistor and a small 8 pin chip but couldn`t read the label. It had burned already one trace on board and likely the transistor also failed. No cooling whatsoever inside. Chinese knock offs are totally waste of time unless they get some custom coolers installed.

I will try to source some pics but can`t promise.

[kur4o]

Some diagram on a similar platform using same ignition parts.