It's official, my P38 is properly sulking. BECM now?

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Ps, thanks Rasheed for the door locks suggestions. I suspect the rf receiver may well be the old sort - was never a problem before as I had no neighbours. Not sure I like this town business.

Will keep an eye on the door locks, but I think that was a symptom of something else - either becm or fuse box...
 
Hi Guy, First thing I'd do is a jump lead from battery -ve to engine block, reconnect battery and see what happens. I've seen all sorts of weird faults when there's a resistance in the earthing and you get can get increased current and odd failures in places that don't make any sense! It's an easy check and if jump lead solves, remove, clean and refit all the earth connections. Also possible they may have disturbed something when working on her for MoT - any welding around cable runs? Dud battery could have caused some issues - less voltage means more current and that can fry stuff too over a prolonged period...

She's probably just having a tantrum because she feels neglected! :p
 
One thing to remember NEVER EVER connect both jump leads direct to the battery on a petrol. Always positive to battery negative to a clean point on engine.
 
Datatek said:
Looking at it more carefully, the BECM could pull the starter relay, I with the others on damp in the BECM.
Click to expand...

But tapping the starter relay seems to stop it...

There's an article on rangerovers.net listing engine cranking as a fuse box symptom. Pretty sure the fuse box can't be burnt though - it's only been on a month! Will have to ask the garage where they got it.
 
kooky_guy said:
But tapping the starter relay seems to stop it...

There's an article on rangerovers.net listing engine cranking as a fuse box symptom. Pretty sure the fuse box can't be burnt though - it's only been on a month! Will have to ask the garage where they got it.
Click to expand...
Damp causes all sorts of strange things, if the relay is not getting full power because it's being pulled by tracking through damp, tapping it may well cause it to drop. Damp in either the fuse box or BECM could cause it.
 
Have a spare fuse box from a '97 4.6 - happy to lend it to you for diagnostic purposes if it helps - with all the relays etc etc.
 
When I said it had got damp, I didn't mean soaking wet. Just a bit condensationy (is that a word)? I read somewhere that the Becm connectors can corrode though. Perhaps I should have pulled them to check while I had the seat out. Something to add to the list, I guess.

Appreciate the offer Fergie. I'm trying to remember the part number for mine now - it seemed to be unusual which is why it was so expensive. Will try and find it out, although I have no idea what the actual differences are.
 
Datatek said:
Damp causes all sorts of strange things, if the relay is not getting full power because it's being pulled by tracking through damp, tapping it may well cause it to drop. Damp in either the fuse box or BECM could cause it.
Click to expand...

I've just been going through the circuit diagrams for this and am coming round to the idea that it could actually be the BECM again. I can see what you mean Keith.

The previous fuse box failed because apparently the starter relay had melted and damaged the fuse box. I had forgotten that little detail which does rather suggest an ongoing issue with this circuit, does it not?

Do we really think sticking the BECM in the airing cupboard for a few days will make any difference? The trouble is, being an intermittent problem, how can I tell if it's fixed it? I'm too nervous to leave a battery connected permanently to it now, especially my huge new one!
 
kooky_guy said:
I've just been going through the circuit diagrams for this and am coming round to the idea that it could actually be the BECM again. I can see what you mean Keith.

The previous fuse box failed because apparently the starter relay had melted and damaged the fuse box. I had forgotten that little detail which does rather suggest an ongoing issue with this circuit, does it not?

Do we really think sticking the BECM in the airing cupboard for a few days will make any difference? The trouble is, being an intermittent problem, how can I tell if it's fixed it? I'm too nervous to leave a battery connected permanently to it now, especially my huge new one!
Click to expand...
Take the BECM out when you have the time, remove the lid and stick it somewhere warm for a week. Check all the connections for corrosion, put it back and see what you have.:)
 
Before I do that, presumably I can check the theory with a meter?

Looking at the wiring diagram, if I do a resistance test between pin 2 on the relay and ground then anything other than open circuit would indicate a short somewhere?

I was trying to decide if measuring the resistance between the relevant pins on the appropriate BECM connectors would tell me anything, but I suspect not, thinking about it. I'm assuming the BECM itself doesn't actually do anything at all with this signal, just passes it through from the ignition switch?

I'd better get myself a new meter - mine's buried in one of my storage units somewhere!
 
The output from the BECM to the starter relay is likely to be a transistor, so it may not present an open circuit on a meter when not active, it will depend on the polarity of the meter probes. I assume the BECM will prevent the starter operating under certain conditions so it's not just a pass through. With the meter on volts, you can check for voltage across the relay pins, should be next to zero until the ignition switch is operated when you should see 12 volts as the BECM grounds one side of the relay.
 
Datatek said:
The output from the BECM to the starter relay is likely to be a transistor, so it may not present an open circuit on a meter when not active, it will depend on the polarity of the meter probes. I assume the BECM will prevent the starter operating under certain conditions so it's not just a pass through. With the meter on volts, you can check for voltage across the relay pins, should be next to zero until the ignition switch is operated when you should see 12 volts as the BECM grounds one side of the relay.
Click to expand...

I'm with you. Will try and test it tomorrow, I've got a new multimeter now.
 
hi, after you have tried every thing, send box to rick the pick,buy new rf receiver, and two new front door latches.then you have done most things,allthough expensive,about 500 all in.
 
Datatek said:
The output from the BECM to the starter relay is likely to be a transistor, so it may not present an open circuit on a meter when not active, it will depend on the polarity of the meter probes. I assume the BECM will prevent the starter operating under certain conditions so it's not just a pass through. With the meter on volts, you can check for voltage across the relay pins, should be next to zero until the ignition switch is operated when you should see 12 volts as the BECM grounds one side of the relay.
Click to expand...

I've just been out with my multimeter, but it's all a bit inconclusive.

Is there a way of tying up the pin positions for the relays with the wiring diagram? One end of what I think are the actual contacts appeared to be at ground but I don't think that helps me at all. I suppose the adjacent pair must be the solenoid side, but it's too dark to continue now.

Interestingly, I've just had a look at my old fuse box which the garage kindly left in the footwell and I cant see anything at all wrong with it. No smell of burning, no scorch marks. Hmm. Pretty hard to imagine how it could seriously cost over £200 too!

I think I will just pull the BECM at the weekend and stick it in the airing cupboard. I'd rather actually find something wrong somewhere though as it doesn't feel like I'm actually fixing anything so I'm not going to trust it much!
 
kooky_guy said:
I've just been out with my multimeter, but it's all a bit inconclusive.

Is there a way of tying up the pin positions for the relays with the wiring diagram? One end of what I think are the actual contacts appeared to be at ground but I don't think that helps me at all. I suppose the adjacent pair must be the solenoid side, but it's too dark to continue now.

Interestingly, I've just had a look at my old fuse box which the garage kindly left in the footwell and I cant see anything at all wrong with it. No smell of burning, no scorch marks. Hmm. Pretty hard to imagine how it could seriously cost over £200 too!

I think I will just pull the BECM at the weekend and stick it in the airing cupboard. I'd rather actually find something wrong somewhere though as it doesn't feel like I'm actually fixing anything so I'm not going to trust it much!
Click to expand...
Take the lid off the relay, then it's easy to see which pin does what. some actually have the pin outs moulded into the top of the cover or base.
 
Datatek said:
Take the lid off the relay, then it's easy to see which pin does what. some actually have the pin outs moulded into the top of the cover or base.
Click to expand...

I don't have any spares so I didn't want to risk breaking any of them. Fair point, but it would be good to know exactly which pin is which rather than having a choice!

I checked pin 6 on connector C177, which carries this connection to the BECM and it showed effectively infinite resistance between it and ground. Not sure if that proves anything going by what you said Keith. I tried the probes both ways round just to check. I'm surprised though. I was sure there would be an obvious earth leak there.

Oh isn't it fun turning your entire toolkit upside down in the dark...
 
Saint.V8 said:
Virtualy all automotive relays have the same pin numbers and switcing logic applied to them

85 and 86 are coil with 30 being the switch input and 87 as NO, 87a as NC and 87b a link to 87
Click to expand...

Thanks for that. Shame they don't print those numbers on the circuit diagram! Actually, just what is the point of the pin numbers on the circuit diagrams for the relays when there is no way of easily identifying them in the fuse box?

I feel sure I must be missing something...
 
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