P38A Signs of a faulty BECM?
- Thread starter Digweed
- Start date
This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
I'd be pulling the plugs out of the BECM and checking them all. I had a window problem and it took ages to find the cause!
One pin on one plug was green, but the pins are tiny and I had to use a mouse tail file to clean it. No bother with corrosion since.
I take it you checked the feed to the fuse board on the side of the BECM?
Mine (and EVERY SINGLE P38...) has a + and a - feed tot he fuse board there, so any of these could also be giving a problem.
As the chaps suggest, the BECM "has" to be working to some degree or the engine would be immobilised
One pin on one plug was green, but the pins are tiny and I had to use a mouse tail file to clean it. No bother with corrosion since.
I take it you checked the feed to the fuse board on the side of the BECM?
Mine (and EVERY SINGLE P38...) has a + and a - feed tot he fuse board there, so any of these could also be giving a problem.
As the chaps suggest, the BECM "has" to be working to some degree or the engine would be immobilised
I finally got the diagnostic tool (hawkeye) plugged in. It's not showing any faults with the becm. It is showing two with the engine, "Charge pressure sensor (B5/1)" and "Needle lift sensor" from what I've been reading on here it might be the turbo pressure sensor for the first one and the No.4 injector for the second, does the BMW 525tds have the same injectors or was there a change with this particular one for the needle valve? As in could I find a scrapped E39 would it have the same type of injector and I could swap it over? The engine has been changed in this thing at some stage I reckon so it's possible that something might not have been reconnected I'll have a better look tomorrow. There was a few more faults "Sensor Right-Hand Front (Short Between Sensors) and three where communication failed between both front seats and the centre console outstation. I'd the drivers seat unplugged at the time and I haven't looked under the passenger seat yet, I've bought a switch pack online and I'll see how that goes. I was able to control all the windows and the sunroof from the hawkeye so the motors are fine. Funny thing is though that there was absolutely no communication between the HEVAC and the tool. The module that had been in the car was damaged, knob falling off, and there was a spare one in the car when I bought it and that doesn't work either, possible that the both of them are fecked. I don't have the adapter yet to check on the SRS/Traction control module so I can't update on that yet.
Datatek
Well-Known Member
- Posts
- 44,886
- Location
- Near Poitiers SW France
"Charge pressure sensor (B5/1)" that would be the MAP sensor on the oil filter housing with a pipe to the manifold. the spigot on the manifold blocks sometimes.
"Needle lift sensor" Check that the connector is OK and the wires are not trapped or chaffed.
You should be able to see both sensors on live data to see if they are operating on a decent Diagnostic tool.
"Needle lift sensor" Check that the connector is OK and the wires are not trapped or chaffed.
You should be able to see both sensors on live data to see if they are operating on a decent Diagnostic tool.
martyuk
Well-Known Member
- Posts
- 824
- Location
- Swindon, UK
Check to make sure you get a connection to ground (with a multimeter on resistance or continuity test) on pin 8 (white wire) of C1276 (18 way white connector on the back of the BECM) when the ignition is in position II
Also check to see if you get a connection to ground (same way as above) on pin 13 (White/Pink wire) of C1280 (16 way white connector under the BECM fuse box) when the ignition is in position I/II
To me it sounds like you have an issue in the wiring loom between the ignition switch and the BECM... or an issue on the power board of the BECM with the Ignition pos II circuit, if you aren't getting power to any of the ignition switched fuses/relays in the underbonnet fusebox.
I've seen it numerous times now where one of those wires between the ignition switch and BECM are faulty and this then stops a whole load of things from working.
Worst case is that it could be the power board in the BECM has a damaged/broken track somewhere which is causing it to not send the correct signal out to the fusebox etc, but I'd start with the inputs to the BECM first and report back.
Only the logic board (lower one) has a PCB lacquer on it to give it some moisture protection - the upper power board doesn't have anything on it.
Also check to see if you get a connection to ground (same way as above) on pin 13 (White/Pink wire) of C1280 (16 way white connector under the BECM fuse box) when the ignition is in position I/II
To me it sounds like you have an issue in the wiring loom between the ignition switch and the BECM... or an issue on the power board of the BECM with the Ignition pos II circuit, if you aren't getting power to any of the ignition switched fuses/relays in the underbonnet fusebox.
I've seen it numerous times now where one of those wires between the ignition switch and BECM are faulty and this then stops a whole load of things from working.
Worst case is that it could be the power board in the BECM has a damaged/broken track somewhere which is causing it to not send the correct signal out to the fusebox etc, but I'd start with the inputs to the BECM first and report back.
Only the logic board (lower one) has a PCB lacquer on it to give it some moisture protection - the upper power board doesn't have anything on it.
Thanks for that, I'll have a look at that tomorrow.
At the minute the only thing that isn't working properly is the EAS and the Hevac. I'm not getting any lights on the EAS switch when I turn on and I can't get it to go up or down. I am hearing a chuff-chuff noise coming from that side of the engine bay for a few seconds when I switch off the engine. I'm guessing it's just a relief valve, but since it hasn't been working before this I'm not sure. I had it plugged in to the hawkeye today to get some live date for the faults it showed yesterday. Don't know whether the boost pressure is right or not but it didn't change when I gave it a bit of throttle, the injected fuel quantity did though.
Attachments
- Posts
- 58,170
- Location
- Preston Lancs.
- Posts
- 58,170
- Location
- Preston Lancs.
Boost pressure at idle should be same as ambient. Injected fuel will change as higher RPM is requested. Boost pressure should rise as RPM is increased.
I seem to have found the cause of my boost pressure problem. It would help if the sensor was actually there in the first place! Can anyone tell me what size pipe comes off it and where it goes? I know roughly the area where it goes to the engine but i can't see where it attaches.
- Posts
- 58,170
- Location
- Preston Lancs.
MAP sensor is bolted to top of fuel filter, it connects with a 5mm ID pipe to a nipple mid way along under manifold. Feel for it. Make sure it is not blocked before fitting pipe.
- Posts
- 58,170
- Location
- Preston Lancs.
Thank you good sir. I'll be happy to be spending the afternoon feeling for nipples!
Dirty boy hope you find a complete firm one.
Datatek
Well-Known Member
- Posts
- 44,886
- Location
- Near Poitiers SW France
Same size pipe as the leak off pipe does the job, needs warming to get it on. Just replaced a broken MAP sensor on my project P38, it ran fine with no pipe, the spigot was broken off the sensor.
Dirty boy hope you find a complete firm one.
Think I found it! Found something about a third of the way from the rear of the manifold about 1cm long with a semi circle of a shroud around it.
found one on Ye Olde Ebay for about 40 euro delivered that has the pipe attached. It'll be next week before I have it.
- Posts
- 19,297
- Location
- Buckinghamshire, UK. ('95 DT)
If it is free then what's to lose?! Or try googling the part number for BMW 525 with M51 and see if it is the same.
You need a socket with a window like the ones for lambda sensors to stop knackering the wire.
- Posts
- 58,170
- Location
- Preston Lancs.
Only adjustment of crack point.
