97 5ltr VT code 49

Wiring diagrams and questions
GTS308
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cars: 1973 308 GTS4 HQ Monaro
1974 HQ Kingswood factory V8 4 speed
1952 202 powered chopped top Morris Minor two door.
1997 HBD VT 5ltr

Re: 97 5ltr VT code 49

Post by GTS308 »

UCMatt wrote:Do you see a corresponding spike on the B+ supply to the distributor sensors?
No the B+ was not being monitored at the time only the cam/D3 line..

Was hopping to have the new BCM fitted today but the guys where flat out so didn't have time to program the key.
If it still has a spike and throws the code I will check the B+, plus the crank sensor signal and see if they spike as well...
But running the car without the alternator should provide a constant supply with if anything votage drop..
If I could do it legally I would just put on a manifold and carby and be done with it...sigh!
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Doctor Bob
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Re: 97 5ltr VT code 49

Post by Doctor Bob »

The BCM has no bearing on this circuit.
the 5v reference is from the PCM, try onitoring is & tapping the PCM
how high does it spike?
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Jayme
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Re: 97 5ltr VT code 49

Post by Jayme »

hmmm heres a thought.... if your 5v line is buggering up over bumps - the TPS and coolant temp sensor and a few others all run off that 5v line, maybe one of those sensors are buggereing up the 5v?? they would be the only things you havent really replaced, and could explain why it still does it when you have replaced everything else.
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Doctor Bob
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Re: 97 5ltr VT code 49

Post by Doctor Bob »

good thought Jaye
GTS308
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cars: 1973 308 GTS4 HQ Monaro
1974 HQ Kingswood factory V8 4 speed
1952 202 powered chopped top Morris Minor two door.
1997 HBD VT 5ltr

Re: 97 5ltr VT code 49

Post by GTS308 »

Doctor Bob wrote:The BCM has no bearing on this circuit.
the 5v reference is from the PCM, try onitoring is & tapping the PCM
how high does it spike?
I know the BCM has no real connection to the PCM apart from sending data back and forth for starting ect, so replacing it is a long shot.
but thinking it is feedback or interference from another part of the vehicle it was just a thought and the BCM is only borrowed so can be returned.
Not sure on how high the spike was..Ill ask the mechanic if he kept the data..
Jayme wrote:hmmm heres a thought.... if your 5v line is buggering up over bumps - the TPS and coolant temp sensor and a few others all run off that 5v line, maybe one of those sensors are buggereing up the 5v?? they would be the only things you havent really replaced, and could explain why it still does it when you have replaced everything else.
So are you saying all the 5 volt outs from the PCM are all interconected and a dodgy sensor connected to those lines could be causing problem?
I would have thought that they would throw their own codes if they were faulty..but then again if it is only a fault for a couple of milliseconds it may not be enough to trip its own code..Hmmmm!
OH just a thought...isnt the knock sensor powered by 5 Volts?...Bump knock sensor Hmmmmmm!

Thanks guys you have given me a new angle to check wednesday...Ill disconnect what I can and still be able to run the car..What I cant I will replace or monitor...
Cheers guys!
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Jayme
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Re: 97 5ltr VT code 49

Post by Jayme »

exactly, there is one 5v line from the ecu, and its all interconnected and powers up everything that needs 5v. the knock sensor isnt powered by 5v, its not powered at all. ill dig up my vt diagram later and make a list of all the sensors that are connected to the 5v. main two off the top of my head is tps and coolant temp, ide say inlet air temp too.
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antus
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Re: 97 5ltr VT code 49

Post by antus »

Looking at the diagram it looks like the crank and cam sensors are B+ powered, and the 5v line is the signal line. So the spike would be related to a spike on B+ or radio interfearance or a bad ground circuit in the area Dr Bob posted above.
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
GTS308
Posts: 16
Joined: Thu Apr 07, 2011 3:51 am
cars: 1973 308 GTS4 HQ Monaro
1974 HQ Kingswood factory V8 4 speed
1952 202 powered chopped top Morris Minor two door.
1997 HBD VT 5ltr

Re: 97 5ltr VT code 49

Post by GTS308 »

I cant say with any certainty that the spike was a supply spike or a spike in the signal. I think the signal voltage is supposed to be between 0 and 1.4 volts (from memory)
As the pulses were being monitored I assume it was the pulse that spiked more than 1.4 volts..Now if this was caused by a increase in the 5 volt line or the 12 volt line that I am not sure.
But as most cars charging systems see votages run from 11 to 15 volts I cant a increase in the 12 volt line causing a problem.
I rechecked both the body and engine earths the other day..No problem there..

I dont know If I metioned this before but when the car was fitted with a aftermarket coil the cam sensor signal was irratic and would throw the code as soon as the car got off idle.
Fitting a genuine Holden 5 ltr coil improved it to what we have now..Only throwing the code hitting a bump..Coil has been moved to a bracket on the firewall from the back of the block..
The radio/tape player was removed from the car right from day one to eliminate this as a source of interference..There is however a little black square block that is bolted to the coil bracket connected
to a plug that is in the wiring loom, I presume this is a radio suppressor although I cant find it on any Holden wiring diagrams...Should I disconnect this as well?

I will have a go wednesday at all that you have suggested Cheers..
wirevt5ltr.jpg
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GTS308
Posts: 16
Joined: Thu Apr 07, 2011 3:51 am
cars: 1973 308 GTS4 HQ Monaro
1974 HQ Kingswood factory V8 4 speed
1952 202 powered chopped top Morris Minor two door.
1997 HBD VT 5ltr

Re: 97 5ltr VT code 49

Post by GTS308 »

Well have not installed the BCM as yet..But on a positive note my mate has offered to come up from Adelaide free of charge and sort out the problem.
He apparently loves a challenge...So if he cant find what the problem is no-one can.
Ill keep you posted..

Cheers.
Mark :thumbup:

mod edit: some details removed by request
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Holden202T
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Re: 97 5ltr VT code 49

Post by Holden202T »

free of charge is not a bad deal!
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