Blanco Posted January 2 Share Posted January 2 I guess I was getting a bit complacent, but I should remember it's a P38, it was all going so well.... Coming home the other night, the dashboard started to light up, fuses 7, 8 and 17 had all apparently blown, and lots of consequential messages followed. The fuses hadn't blown, it is a reasonably common issue with the BECM. I removed and examined the BECM, and actually to my inexpert eye it didn't look too bad (not nearly as bad as the one from my parts car), I did a bit of a clean up, using Servisol switch cleaner (I think @FridgeFreezer recommended that to me a while back) most of the green crusties and water marks cleaned up except for two areas, Centre of the pic above there is a white mark which I thought was just lacquer, but looking closely there is some other discolouration I am not sure of and... here there are two large solder joints that wouldn't clean up, I'm not sure what causes this discolouration. Elsewhere there were some black deposits around a connector which mostly cleaned off but I don't seem to have pictured those. Anyway long story short it was no better after my efforts to clean up, I even got one more fuse added to the list! I know there are a couple of outfits in the UK that repair these but they want me to send the engine ecu, becm and a key into them. I was hoping to avoid the extra delay and just get a known good becm sent out to Ireland. Which brings me to the question. I know they are coded to the car, but I gather that the code is in the logic board, and the damp and water damage generally just affect the power board (as above), has anyone here tried swapping their own logic board into a.n.other becm and successfully got going again?? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 2 Share Posted January 2 Isn't there a big guide to everything inside the BECM on a site like rangerovers.net or something? The brown stuff is just solder flux from manufacturing, very unlikely to affect your BECM. I suspect there's no great rocket surgery in repairing them, it's old tech now - let's see some more pics of both sides of the board for starters if you can be bothered. Quote Link to comment Share on other sites More sharing options...
Blanco Posted January 2 Author Share Posted January 2 Haven't found such a guide yet, .... I definitely can be bothered, thank you,.. I will go and haul it back out from under and post some more pics, back half an hour or so.... Quote Link to comment Share on other sites More sharing options...
Blanco Posted January 2 Author Share Posted January 2 More snaps, These two are the logic board, and then .... These show the power board, the last detail is where the black residue was that didn't entirely clean up, behind the green connector Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 2 Share Posted January 2 1 hour ago, Blanco said: Haven't found such a guide yet, .... I'll shout @TSD @elbekko as I'm sure it was one of them who mentioned it... having not looked inside a BECM my 1st port of call would be to work out where the "faulty" circuits come into the unit (which plug(s) / pin(s)) and trace through from there, to mis-report a blown fuse suggests it's measuring voltage on a pin and not seeing what it expects to see, could be a bad solder joint or a failed component on the sensing circuit. Quote Link to comment Share on other sites More sharing options...
Blanco Posted January 2 Author Share Posted January 2 Relay 10 seems to be the culprit, although doesn't look damaged. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 2 Share Posted January 2 Could easily just be a corroded or worn out contact. 1 Quote Link to comment Share on other sites More sharing options...
Blanco Posted January 2 Author Share Posted January 2 2 hours ago, Bowie69 said: Could easily just be a corroded or worn out contact. Meaning I should change that relay? RL6 is the same type, I have a spare board which is otherwise poor but has those relays on it... I could bring a battery indoors and test their operation ( It is generally 'kin wet and unpleasant outside at the moment!) Quote Link to comment Share on other sites More sharing options...
Blanco Posted January 2 Author Share Posted January 2 ...... kind of assuming 12v is correct for the testing I guess? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 2 Share Posted January 2 1 hour ago, Blanco said: Meaning I should change that relay? RL6 is the same type, I have a spare board which is otherwise poor but has those relays on it... I could bring a battery indoors and test their operation ( It is generally 'kin wet and unpleasant outside at the moment!) You could, or often you can pop the cover off even these soldered relays and take a look at the contacts, and clean them up. 2 Quote Link to comment Share on other sites More sharing options...
Blanco Posted January 2 Author Share Posted January 2 Thanks Bowie, I'll practice on the spare one and report back tomorrow Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 2 Share Posted January 2 2 hours ago, Blanco said: ...... kind of assuming 12v is correct for the testing I guess? For the contacts yes, the coil side could be 5v as that'll most likely be what all the logic runs on - that or 3.3v but I think automotive stuff stuck with 5v for quite a while for robustness. 1 Quote Link to comment Share on other sites More sharing options...
elbekko Posted January 2 Share Posted January 2 5 hours ago, FridgeFreezer said: I'll shout @TSD @elbekko as I'm sure it was one of them who mentioned it... having not looked inside a BECM my 1st port of call would be to work out where the "faulty" circuits come into the unit (which plug(s) / pin(s)) and trace through from there, to mis-report a blown fuse suggests it's measuring voltage on a pin and not seeing what it expects to see, could be a bad solder joint or a failed component on the sensing circuit. Can't recall anything other than the BeCM SID document: http://rave.stringsandints.com/BECM SID CONSOL.doc Overall that BeCM looks very clean. Mine looked a damn sight worse after that Welsh creek Contact cleaner and a paintbrush and toothbrush are your friends for cleaning. I think one of the main things the recon companies do is replacing old capacitors. Might be worth a try as well, shouldn't be that hard to DIY. As for swapping only the power board, I think that's definitely worth a try! 1 Quote Link to comment Share on other sites More sharing options...
Escape Posted January 3 Share Posted January 3 If you can't find the cause and/ or fix it, a bit of info on replacing the entire BeCM, as I did just that a couple of months ago. Ideally you want to take a screen shot of all the settings before taking the old one out. The replacement one will only respond to the original keyfob, but you can change the blade and swap the fobs without needing to do any more coding. For the engine ECU, you need diagnostics that can relearn the security code. I found most of my time was spent getting the old one out because of access under the seat. Once the 'new' one was in, it worked straight away. Quote Link to comment Share on other sites More sharing options...
Blanco Posted January 3 Author Share Posted January 3 Update,... had a close look at these relays and the covers can't be removed (at least not tidily) unless you take the relay off the board. I have treated myself to a new soldering iron from Amazon and will try my hand at desoldering when it gets here (Friday) more anon. Quote Link to comment Share on other sites More sharing options...
Blanco Posted January 13 Author Share Posted January 13 Update.... Amazon let me down, I am still waiting for one parcel (Their deliveries seem extended after Christmas?) In the meantime I had also ordered the cheapest BECM from ebay £53, .... (£84 by the time Pitney Bowes had added it's bit on). That turned up and I opened it up and was delighted to find it as clean as anything inside, so plan B was to swap in my logic board, which I did, and 30 mins later the car ran faultlessly,... chuffed with that. So if anyone else runs into a similar problem, that is a good solution. When Amazon gets here, I will swap in a good relay to my old BECM and file it away in a plastic bag, in case of future need. 3 Quote Link to comment Share on other sites More sharing options...
elbekko Posted January 13 Share Posted January 13 Glad to hear that's an easy option! Will keep it in mind for the future Quote Link to comment Share on other sites More sharing options...
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