pcmhacking.net

1.8v is a common voltage breakdown of the 8192 standard, almost twice of the logic comparative of 80% @ 5v, but it is drain based so makes even more sense.

i have disconnected the PCM and received the same incoherent chatter.

It would be an easy confirmation, i will rifle over the manual and try and find a testing procedure for the PCM.

Testing for PCM is easy enough for everyone else, disconnect the the bcm fuse under the bonnet and voltage test the serial data (pin9->body/earth) on the DLC.

Just found the dash has 26 error codes it can report, 7 of which are serial data based (abs missing, bcm, ecc, sdm, bcm no polling, general serial data missing).

this could be interesting.

edit: bah, it will only be relevant to aux bus line, am im pretty sure that is working

ok, trying to figure out whats been done..... exactly what modules have you unplugged when you said 'disconnected all modules'

Eleanor wrote:1.8v is a common voltage breakdown of the 8192 standard, almost twice of the logic comparative of 80% @ 5v, but it is drain based so makes even more sense.

i have disconnected the PCM and received the same incoherent chatter.

It would be an easy confirmation, i will rifle over the manual and try and find a testing procedure for the PCM.

Testing for PCM is easy enough for everyone else, disconnect the the bcm fuse under the bonnet and voltage test the serial data (pin9->body/earth) on the DLC.

Not sure what you mean by "1.8v is a common voltage breakdown of the 8192 standard". The idle voltage for ALDL is 5V.

The chatter will be from the BCM, apparently (from my readings) this is normal for a VT.

Also, if the PCM is damaged, simply disconnecting its fuse won't make the ALDL voltage recover, since the damage is likely to be around the transceiver.

Joe.

Eleanor wrote:edit: bah, it will only be relevant to aux bus line, am im pretty sure that is working

Not really. Except for that 5 second thing I mentioned earlier, on a VT, the secondary bus is normally connected to the primary bus via a relay in the BCM. So either both work or both don't.

Joe.

the only follow up question is, is the microcontroller the relay and is it itself corrupted.

if its not there are many reasons why its not relayed in the subcomponents, first being that it would be unnecessary bandwidth consumption.

as im not an engineer, i dont even know most of whats on the board.

when i spoke to my mechanic, he stated they are very prone to short circuiting/head banging. again, i draw upon the fact im not an engineer.

ultimately, the parts are simpler to reproduce (with a little hindsight), than to source up from your friendly wreckerologist. but we are forever travelling the slower path.

Eleanor wrote:the only follow up question is, is the microcontroller the relay and is it itself corrupted.

if its not there are many reasons why its not relayed in the subcomponents, first being that it would be unnecessary bandwidth consumption.

The relay is within the BCM. Your evidence to date (if you really disconnected everything but the PCM and got a steady 1.8V on the ALDL data line) is that it's your PCM that's cactus. Therefore, there is no evidence that something's wrong with your BCM microcontroller.

Your speculation about bandwidth notwithstanding, the primary and secondary ALDL data lines are indeed normally connected (via that relay) on VT+.

Joe.

I'd say disconnect the aldl bus outside of the pcm and measure it. with nothing else, not even a bcm you should see the vats data. if you dont the issue is pcm. if you do, then issue is somewhere else on the data bus.

Hi Eleanor,

Just wondering, was there a resolution to this?

Joe.

sorry for the delay, i'm trying to detach from the problem because im stone walled...

i tried to replace the BCM, when i plugged it in the same signal/pulse was being transmitted on the data line. Also removed the solar/receiver module under the windscreen.

its either my homebrew module and all my effort was in my head lolz, or something very atypical.

a few thoughts did go through my head, the PCM enable diag resist (10k) wasnt accurate, some sort of handshake/pullup required on connection, BCM was in lockdown because of the SRS error.

I made a few other observations, the simplest to share is, that the abnormal signal (IMO) occurs straight after the 8pin is plugged in, the 8 pin has power, earth, Anti-T Led, demist, wiper (in wagon which mine isnt). I could be wrong as im using the pdf of a "low" model bcm. Furthermore, the led could i spose have some sort of abnormal power effect on the circuit.

But im done with it, going to solicit a professional for a solution that doesnt involve banging my head on a wall.