1997 F-Body ECM

[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.

[Tom H]

Gm looked like knock module inside, had some fat transistor soldered to back steel plate to enhance cooling, and some small factor custom chip.

Just a WAG from me: Chip drives the gate (base?) of the transistor and provides over current protection. Transistor drives the coil based on the input from PCM. Want more dwell? -> fatten the pulse from PWM. Too much dwell make the pulse less wide.
These are all things the TPU does very well.
Chip is probably there to drive the output transistor and shut things down if there is a short.
I need to get hold of one of these and have a look-see.

Look forward to the pics if you can

-Tom

[kur4o]

Some diagram on a similar platform using same ignition parts.