Advice needed on VT hardware

Information and discussion of EFI hardware and specifications
Eleanor
Posts: 12
Joined: Mon May 25, 2015 4:48 pm

Advice needed on VT hardware

Post by Eleanor »

I have struck a problem with a rebuild. As i want to keep this simple i will for-go the pretext for now.

I believe i need to replace the PIM as im unable to connect to the bus using ALDL, it looks like class 2 data, not idling at 5v even when IGN is off.

My question is, what is the easiest suggestion for replacing the PIM in this day and age.

I believe im seeing affordable PIM's on ebay that appear blanks, although they are advertised for GEN 3. As it's just a proxy and should have the basic framework, im thinking they would be appropriate.

Ultimately any pricing info or options would be greatly appreciated.

Edit: Should mention its a straight v6
User avatar
antus
Site Admin
Posts: 8239
Joined: Sat Feb 28, 2009 8:34 pm
cars: TX Gemini 2L Twincam
TX Gemini SR20 18psi
Datsun 1200 Ute
Subaru Blitzen '06 EZ30 4th gen, 3.0R Spec B
Contact:

Re: Advice needed on VT hardware

Post by antus »

The only VT that should have a PIM is the LS1 as the engine computer talks VPW. V6 or 5L v8 will not have a pim and will be straight ALDL.
Have you read the FAQ? For lots of information and links to significant threads see here: http://pcmhacking.net/forums/viewtopic.php?f=7&t=1396
Eleanor
Posts: 12
Joined: Mon May 25, 2015 4:48 pm

Re: Advice needed on VT hardware

Post by Eleanor »

while i have your attention, could i ask if you understand what is going on, i cant see any predictable 8192 data, voltage is irregular when car isnt in IGN/diag mode.

the tool works fine on the VS and i thought they were practically the same protocol wise.
User avatar
antus
Site Admin
Posts: 8239
Joined: Sat Feb 28, 2009 8:34 pm
cars: TX Gemini 2L Twincam
TX Gemini SR20 18psi
Datsun 1200 Ute
Subaru Blitzen '06 EZ30 4th gen, 3.0R Spec B
Contact:

Re: Advice needed on VT hardware

Post by antus »

Are you checking this with a scope? I'd say most likely fault is one of the devices on the bus has died. Most likely options are BCM and ABS. Try unplugging 1 or the other and key on without starting the engine and see what you can see on the bus then. You should see the security requests coming out of the pcm looking for the bcm.
Have you read the FAQ? For lots of information and links to significant threads see here: http://pcmhacking.net/forums/viewtopic.php?f=7&t=1396
Eleanor
Posts: 12
Joined: Mon May 25, 2015 4:48 pm

Re: Advice needed on VT hardware

Post by Eleanor »

you have given me a great direction, thanks for your responses.
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 »

On VT, ALDL (pin 9) connects directly to BCM, thence via a relay to PCM, etc. (Edit: BCM & PCM, thence other devices.)

From memory, when you turn the ignition on, the BCM will open this relay for 5 seconds, thereby briefly disconnecting the other ALDL devices. Observing the ALDL behaviour during this time may give a clue to where the fault lies. (Edit: See below.)

Joe.
Last edited by j_ds_au on Sun Jun 14, 2015 12:14 am, edited 2 times in total.
Eleanor
Posts: 12
Joined: Mon May 25, 2015 4:48 pm

Re: Advice needed on VT hardware

Post by Eleanor »

replying just for those with general interest.

what i observed when plugged in is a single character being transmitted 13 times (pattern).

Sometimes its 0x4, sometimes its 0xC.

it reminds me of a capacitor somehow impeding on the line, very superficial but appears to have logic because of expectation and pattern.

when the car is switched to IGN, the same character is being transmitted, but varied lengths between a sizable pause in communications line.

everything else is working, when i confuse the BCM the PCM will switch the radiator fan to suggest the break down.

:)
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 »

I've read somewhere that ABS modules are known to fail and disrupt the ALDL data bus. Don't know how true that may be.

Did you monitor the ALDL data line with a voltmeter directly after turning the ignition on, looking for a 5 second change?

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

Re: Advice needed on VT hardware

Post by Eleanor »

- i have disconnected all modules and repeated tests (both fuse and plug methods)
- pcm serial line voltage is 1.8v steady, bcm + pcm is variable even when ignition is off
- no predictable aldl communication even after IGN is switched
- no noticable scorching on the board

given the board doesnt have alot of capacitors, im thinking its the crystal/rf receiver thingie or a voltage regulator, but nothing noticable.

time to throw in the towel and get a mobile mechanic out to resync some repurposed stale cake (bricks for paper weights me thinks)
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 »

Methinks the PCM is stuffed. "1.8V steady" just isn't sensible, it should be 5V if the other modules are disconnected (and the PCM is properly powered). I'm assuming there's an internal pull-up resistor, like in earlier PCM's. As for ALDL activity when the BCM is connected, ignition off, apparently that's normal for a VT (yeah, as if battery drain wasn't bad enough already!).

Also, I need to correct what I said previously about the 5 seconds ALDL disconnection thing for VT(+), it's a bit more complicated ... firstly, the PCM is hard-wired to the BCM, it's all the other modules that connect via a relay; secondly, you'd need to induce VATS failure, say, by placing some insulation on the key reader slip ring.

Joe.
Post Reply