Advice needed on VT hardware

Information and discussion of EFI hardware and specifications
Charlescrown
Posts: 1831
Joined: Sat Aug 06, 2011 7:58 am
cars: V8 VR Commodore BT1
LB Lancer 2L turbo & Delco
Starion TBI with Delco
Mitsubishi Lancer EVO4 track car
NA MX5
3 vintage motor bikes
Location: Padstow NSW

Re: Advice needed on VT hardware

Post by Charlescrown »

Try just unplugging the ABS. The VT is notorious for the ABS pulling down all communications. With the ABS unplugged try again and if you get engine data the problem is the ABS module. Good luck.
User avatar
j_ds_au
Posts: 384
Joined: Sun Jan 25, 2015 4:21 pm
Location: Sydney

Re: Advice needed on VT hardware

Post by j_ds_au »

Eleanor wrote: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. :comp:
Yeah, you need to step back a bit to see things more clearly.

OK, as stated before, signals/pulses from the BCM are apparently normal for a VT. Did you try replacing the PCM (instead)? Did any of these changes get you a 5V idle state on your ALDL line (especially during that 5 second interval for which you can induce the BCM to disconnect the secondary ALDL devices)?

I can't comment on your homebrew module as you haven't provided details, but presumably the voltage measurement you made earlier excluded this. I also presume the LED you've mentioned has no connection with the ALDL line.

A 10k resistor is not needed for ALDL comm's on a VT. A/the 8 pin connector is not relevant unless it goes to the OBD connector or PCM.

Joe.
Eleanor
Posts: 12
Joined: Mon May 25, 2015 4:48 pm

Re: Advice needed on VT hardware

Post by Eleanor »

I've had your question a few times, thanks for sticking with your strongest line of questioning.. let me try to satisfy.

i have disconnected everything i can think of and yes the volt monitor was external from the modules, its just a simple multimeter meter. (best to repeat at this point that i get the same results from another bcm)

The voltage is pulsing for lack of a better word, with each module disconnected, and is present when the BCM has the "8 pin" connector only, plugged in.

the 5second interval is not evident, the behaviour is as follows, it repeats 13 groups of $4 (0x4, 4h etc) in each packet, my module has a basic idle count (combination of microcontroller and imposed short delay) timeout for packet handling for best response/interpretation.
when the ignition is switched the packets are varied the same character is transmitted but in random lengths, and it doesnt go quiet.

I hope i answered some of your queries with this :)
User avatar
j_ds_au
Posts: 384
Joined: Sun Jan 25, 2015 4:21 pm
Location: Sydney

Re: Advice needed on VT hardware

Post by j_ds_au »

OK, it sounds like your module is some kind of microcontroler device for monitoring the ALDL comm's.

Anyway, you seem to be concentrating on the chatter coming from your BCM as the cause of your ALDL comm's issues. However, this is supposedly normal for a VT, so you need to look at what's not normal, which is the 1.8V idle state on your ALDL bus.

There were indications in your previous tests suggesting the PCM was to blame, yet it's still not clear if you've tried swapping that.

It is also possible that something else is pulling down the ALDL bus, notably ABS. You can induce the BCM to disconnect the secondary ALDL devices for 5 seconds by turning on the ignition key, but preventing the key reader operation, either by using suitable insulation over the reader ring or using a spare key that doesn't have the electronics.

So in summary, you need to be looking for why you aren't getting about 5V for your ALDL idle state, because it's highly probable your 1.8V isn't enough for the ALDL devices to communicate.

Joe.
Eleanor
Posts: 12
Joined: Mon May 25, 2015 4:48 pm

Re: Advice needed on VT hardware

Post by Eleanor »

it is 5v definately not idle though
User avatar
j_ds_au
Posts: 384
Joined: Sun Jan 25, 2015 4:21 pm
Location: Sydney

Re: Advice needed on VT hardware

Post by j_ds_au »

Eleanor wrote:it is 5v definately not idle though
That's more like it!

OK, your idle voltage level is now correct (BTW, what was pulling it down to 1.8V?) and your BCM is happily chatting away, so you should now be able to talk to your PCM, unless there's something wrong with it. At this point, the simplest way to check your PCM is alive is to do the paperclip test (but be careful, don't damage the contacts of your OBD connector), you should see a 12 code flashing on your Check Engine Light (and any other trouble codes, if they exist).

Joe.
User avatar
VL400
Posts: 4991
Joined: Sun Mar 01, 2009 2:54 pm
cars: VL Calais and Toyota Landcruiser. Plus some toys :)
Location: Perth, WA
Contact:

Re: Advice needed on VT hardware

Post by VL400 »

On a VT and later the paper clip test for flashing the CEL needs to have a working data bus as its ALDL sent to the cluster in one of the status messages (BCM requests the PCM to send data out to the cluster).

You can log a VT PCM with no BCM connected, the flashtool can also connect by selecting the bench preference. So a good test that it is working is to jut have everything disconnected excpet it from the bus, it will be silent. Connect using the flashtool and do a get bin.

The BCM will always be spewing out data, so remove all ALDL modules from the bus except it. Open the flashtool, set it up to listen and you should see a bunch of data - if not then that could be your problem. Plug in one module at a time and repeat, as has been mentioned the ABS is the prime suspect for a ALDL bus issues.

Here is an example of what you should see .. http://pcmhacking.net/forums/viewtopic. ... ging#p8639
As its a bench setup there are some modules missing but will give some idea, its just missing the responses from the ABS and SRS.

Still confused as to what your ALDL module is though!
Eleanor
Posts: 12
Joined: Mon May 25, 2015 4:48 pm

Re: Advice needed on VT hardware

Post by Eleanor »

VL400, your first statement interests me... the paper clip does work, and anti-theft works so it must be my listening tool.

firstly, its weird because the listening tool works well on the VS i have, i can execute commands and it returns data that was predicted...

the module i made consists of a pic24fj64gb002 and a few other bits and pieces, runs off of 3.3v, 5.5 absolute max digital pin tollerance, usb, android interface.

with a second thought though, i have disconnected the various devices including the srs by two means, last was the connector near the window switch when i was testing the solar sensor and remote receiver.

my last test by connecting only the power plug (which has a few misc other things on it), didnt listen to the data but it wasnt idle which concerns me despite the re-enforcement provided here.
User avatar
j_ds_au
Posts: 384
Joined: Sun Jan 25, 2015 4:21 pm
Location: Sydney

Re: Advice needed on VT hardware

Post by j_ds_au »

VL400 wrote:On a VT and later the paper clip test for flashing the CEL needs to have a working data bus as its ALDL sent to the cluster in one of the status messages (BCM requests the PCM to send data out to the cluster).
So the CEL isn't directly controlled by the PCM in VT+? Instead of an extra trouble code on the CEL due to a faulty ALDL, the user is kept in the dark - hmmm, that doesn't seem like a sensible design choice!

Joe.
Post Reply