pcmhacking.net

It was a interesting day for all. I was tied up for most of the day only had a chance to drop in late afternoon.
Daryl found the when using the engine as a earth source voltage was down 1/2 a volt. Running a earth from engine mount to body corrected this.
This may have been the cause of the spike..but having said that it did not cure the problem.
Daryl tested every sensor, power supply, earth ect under the bonnet finding only the above earth problem only.
He assures me the problem is not in the engine bay....

The oscilloscope shows a perfect pulse to the PCM all the time while the vehicle is running with no spikes or misses but the PCM throws the code still.
The PCM was changed back to my original one including chip and it still throws the code 49, sometimes afer a few minutes sometimes after 10 minutes.
He has tested all wiring to the PCM including earths and power supply and found no problems...Daryl has gone back to Adelaide to try to find someone who programed the PCM's for the VT's
as he thinks it is a programing fault .....probably be my luck to find there was a batch of faulty PCM's and I just happen to have two of them..

Stay tuned

You havent got a mobile phone kit or similar causing electro magnetic interference new the ecm have you .I take it the wiring harness is well away from ht leads /coil.?

Kloppy is now a part owner of Roaring 40's with Paul Bottomley
http://www.roaringforties.com.au/About.aspx

Not sure about Warwick but believe he is still at Holden.

yoda69

Thanks Doctor Rob and Yoda69 I will pass the info on the Daryl if he does not already know.
vn5000 My VT is a dead stock Holden by design right down to the radio/tape player only mod is extractors cats and exhaust.. oh and lambs wool seat covers.
No aftermarket gadgets at all as far as electrical goes.

Wiring was shielded with foil and tested still had the same problem..

Warrick is still doing the rounds,Darryl last visited my way about 2 years ago and Paul Bottomley i met 3 years ago at Cobram and took me for a spin in his "noisey boat"
I think it was a 340 or 360 chrysler, and delcoed from memory.....one funny dude!

Been having a think about this one too, a code 49 happens if you get less than 8 ref pulses between a cam/sync pulse - after 10 times it throws the code. So either, the ref pulse gets missed, there is noise being picked up on the cam pulse and its counting some extras or there is software bug - its pretty much the same code in the V6 A5 code though.

What broadcast code is your memcal? CJDN?? If you can log data using TunerPro (or any scan tool that you can setup custom commands) can actually monitor the two bytes of RAM that relate to code 49 - the cam sensor counter for each time the cylinder count is > 8 with no cam pulse and a timer byte.

Might be able to tell you if you get a whole heap of cam missing counts in a row or if its just the occasional one missing that eventually adds up to 10 fails. It can be very very hard to pickup a single missing cam pulse on a scope

Im pretty sure its a CJDN. I didn't know you could actually monitor the ram, but that would be a good option to try.
The pulses were recorded on a lap top and reviewed pulse by pulse afterward in fractions of milliseconds..The vedict at this stage is its a software problem.
I was tempted just to drop a carb and manifold on it but thats frowned apon by the boys in blue..Another option is to reprogram the PCM so that runs pulse injection like a VR
but doing this would keep the car around 25hp down from what it should be...Oh well see what happens!

Cheers

who gave you that figure? I put it to you to prove it lol, old batch fire isnt that bad for power, sequential mainly helps out economy.

Spot on Jayme.
When you're at WOT and the injectors are at 80% duty cycle it makes little difference when they start to open as they're open nearly all the time.
Main improvement with sequential is actually emissions, idle and small throttle inputs and some very small economy gains.

I'd be more worried for what is a basically stock setup it's throwing codes, definitely points to something wrong somewhere or otherwise forums would pick it up as a common problem. Can't imagine it being software, or everybody would have the problem.

Given you've replaced nearly everything electrical, about the only thing left is the alternator itself and the relay for the power to the PCM.
2 things to try would be gently tap alternator when vehicle running and also try the same with the relay to simulate hitting a bump.
Would possibly also check all wiring from the alternator to ensure that none has been damaged, try moving it around a bit with the engine running to see if it causes a problem.

These are all real long shots, but you've basically replaced everything else.

yoda69

Can use ALDL mode 3 to request 6 data bytes of RAM - you just specify 6 address' of interest. In CJDN two bytes for malf 49 would be 186F (Malf 49 fault counter) and 1843 (the cyl counter, 1-8). So could request those along with 4 other address' and see exactly when the fault occured (Malf 49 counter incremented), if you have a scope on the ref and sync would see which pulse was the culprit if its not a software problem.

Depending what you have access to (EPROM programmer?) could do a little mod to an ALDL mode 1 frame and get some really fast logging happening. At 800RPM you have the cyl count incrementing at 50 odd Hz, could prob get about 45Hz so would be very close to seeing every ref pulse and watch the cyl counter increment.