99 Isuzu 3.5 anyone know about these ECUs?

[jim_in_dorris]

Good news is 68hc11's are well documented. Hopefully your assembly skills are up to the task. I also think that a picture of the exterior of the ecm showing connectors might be of help. Grab an easy chair and start researching how the chevy guys dis-assembled the prom. IIRC the thirdgen site has some good writeups.

[CyrodiilSavior]

Here is the pinout for the 3 connectors for the PCM
2012-04-26_132003_conn1.gif
2012-04-26_132017_conn2.gif

[1project2many]

Interesting. That looks very similar to the Daewoo / Delco PCM that I obtained years ago with a 2000 2.0 DOHC GM / Daewoo engine. The big brother to this four cylinder is a 2.2L engine. A version of the 2.2 is available in the Trooper. Looking at pictures of the 2.2 and 3.5 Trooper ECM's convince me they are very similar.

When I started playing with this ecm there were few tools built that allowed one to attempt to unlock and download the pcm code through the diagnostic port. Today there are a few. One might allow you to use the GM algorithm to cread a key from a manually requested seed. I don't know if this is the best approach but it is one way to start.

[CyrodiilSavior]

Looks like you're definitely right! If anything the outside box and connectors are identical to the 98/99 trooper PCM
s-l400 (1).jpg
s-l400 (2).jpg

[CyrodiilSavior]

Small update: a friend of mine sent me this apparently there is a hidden plug underneath the plastic bit seen in the pictures above. I saw it on a couple other GM ecus from around this time period. Is this possibly a way to interface/program the system?
44931129_2301240213238033_5438219789841465344_o.jpg

[1project2many]

The plastic bit is usually called a "knock filter." In older ecm's the knock filter contained circuitry to filter noise from the knock sensor so the ecm could focus on real knocking. The plug is standard to other GM ecm/pcm units using a similar knock filter design. I don't know of anyone using that plug to access the code.

[Xnke]

It is not a data port, it is an analog filter plus an amplifier, and an analog-to-digital converter.

Same part is used on the 2.8/3.1/3.4L P66 PCM's. You have a P6-style computer, but it's got P66 style programming. Not currently well studied-but you might start with the flash routines for the 94/95 OBD 1.5 computers used for the 3.4L V6 and LT1 V8 computers.