Help Identifying Mystery Protocol

[Rerouter]

I have an old bit of hardware that the diagnostic tool is beginning to go intermittent, and its potted, making me think, can i build a replacement.
But first i am trying to figure out what standard (if a standard) it may be?

Physically it is a 1 wire bus with a 10K pullup to 24V, and an open collector to send on the device side
The interface is used to read out diagnostics from an automotive controller from roughly 1995

Pulled out the logic analyser, and protocol.png shows what i am seeing.

So far what i have worked out is, its 1 bit per ms, or 1000 baud,
every 32ms it pulls low for 450us which i am going to assume is packet start

It then sends 31 bits encoded like below

pull low for  90us for i assume a 0 value,
pull low for 275us for i assume a 1 value.

ending in "0101" or "0000" if the device is in reset it only logs "0000" on the last 4, so i am guessing an ACK / NACK

A few of my crude decodings hint at values being stored in groups of 7 bits, this is how i have roughed out my excel sheet in the decode picture
however that would imply the start bit gets read as a 0 in all cases (7x4 + 4 = 32) as such on my excel shee i have added a 0 to the front of the binary.

Any insight if you have seen such a thing before, and any thoughts on an implementation other than bit banging?

[max_torque]

Is it a GM or Ford ecu by chance?  Running one of the J1850 PWM protocols?

[Rerouter]

Its out of a seimens brand device, an electronic throttle controller.but its a general purpose device produced by seimens,

It does very much resemble a PWM protocol, but doesnt look to decode the same, and has a much lower baud rate than the standard,

I've gotten a defective device (damaged output) that i can play with, so will attach a logic probe to the devices internal TX line to try and tease out some more info on the protocol.