[exoray]

So my 2008 335i suddenly started overheating on the fwy about a month ago. We got it towed back home and luckily there didn’t seem to be any mechanical damage done. Looking through the car, we couldn’t find any leaks from a pressure although it did not hold pressure perfectly at 15psi. While there was no CEL I plugged the code reader in and got 2E83, 2E84, 2E85, as well as 2DEC, 2DED, and 2AB4.
The car had died over the time I’d left it sitting which isn’t too crazy considering it was a month but now it will keep draining to around 9v from 12.1 overnight. This has me thinking it’s and electrical fault somewhere. I’m suspecting a blown fuse possibly but that doesn’t explain the draining battery unless a weakening battery somehow blew the water pump fuse. In addition, my ECU fusebox in the hood doesn’t appear to be like any of the turbo layouts but rather a 2008 and newer non-turbo’s with some additional relays. I don’t know where to find the water pump fuse at this point. Does anyone have any suggestions on where to start? I’m not eliminating it as a possibility but my water pump was replaced less than 10k miles ago so I don’t think it’s likely the water pump.

EDIT: Problem turned out to be a blown diode(and probably some other parts) in the water pump between 12v continuous power and ground pins. This whole thread has logged my test methods. If you are in denial that it's the water pump because it's your nth one, you can follow the thread as it's a compilation of all possible things other than the water pump that could bring about 2e85 or 2e84 codes.

[WRichieX]

How old is your battery? A bad battery can cause a lot of headaches for these cars. Also, I read somewhere that a bad coolant temp sensor could cause communication errors. I would start with replacing the battery first.

[exoray]

Originally Posted by WRichieX

How old is your battery? A bad battery can cause a lot of headaches for these cars. Also, I read somewhere that a bad coolant temp sensor could cause communication errors. I would start with replacing the battery first.

I thought that might be it so I ran a test by unplugging the battery and checking the voltage over 6hrs and it didn’t really drop below 12v. I’ll check the coolant temp sensor next to see if that’s keeping the pump from running.

[exoray]

So an update: I was gone for a week but came back and checked out some more things from my research. I tested the alternator’s diodes and it seems to be the issue but the readings are a little inconclusive. When I checked with my multimeter in the diode setting, both ways gave similar readings of 33? I made sure it wasn’t a multimeter issue by testing it on other car’s alternators but they gave proper readings. So what could this mean? The diodes are just gone or shorted somewhere in the coils so there is little resistance going both ways? It appears to be an alternator fault for sure looking at the symptoms.

[exoray]

Another update: my multimeter was funny and after re-measuring, diodes seem fine. Everything else in the BSD line is working then, so i will try cleaning the water pump connector and see if the will help.

[exoray]

More updates in case somebody finds this thread and I resolve it in the future: the oil level sensor, ibs, and alternator all seem fine from testing them by running and unplugging each to see the codes and read outs. Doing a drain test and unplugging the 50 amp fuse in the dme box showed drop in amperage so my guess is that there is a short after the dme box but will confirm with water pump cable voltages. If it’s the water pump, how can a 2e85 be thrown while there’s a parasitic drain? Biggest suspicion is in fact a short

[exoray]

So after doing some more digging, I narrowed down the issue to something in terms of wiring after the f07 fuse. when that fuse is connected, the alternator seems to read current flow in both directions and when the fuse is pulled the diodes appear to read like they should. The same goes with the drain, when the fuse is plugged there is a read drain of 90ma and when removed it is around 20ma. The best guess is that there is a continuity issue with the 12v direct current line that goes to the water pump somewhere after the f07 fuse. It would explain the weird reading from the alternator since the two both connect to the battery from the same location right next to the DME box so the current takes the shortest path to the ground, somewhere on the 12v water pump line that's shorted making the alternator simply read a ground to ground voltage drop instead of across the diode. Anyone have any ideas of finding exactly where?

Edit: In short the supposed area for the short is in the x8684 connector to the water pump

[Hottie335]

Same bro I have a similar issue except my battery doesn't seem to drain but pump doesnt run at all. Codes 2e84 water pump missing even tho replaced it twice along w the t stat. First thought it was my water pump electrical connector since the pins on my pump I replaced seemed to have been burnt through so I was thinkin connectors prolly ducked as well. Spliced on new connector but nope waterpump dont even run at all. Man these cars are a pita I've given up and will be takin it to a workshop tomorrow. I'd love to help but man the amount of changes bmw has made with these fuses is ridiculous to sort through and when it gets this complicated I'd rather just give it to a shop at this point tbh. Good luck lmk how urs goes👍🏽

[exoray]

Originally Posted by Hottie335

Same bro I have a similar issue except my battery doesn't seem to drain but pump doesnt run at all. Codes 2e84 water pump missing even tho replaced it twice along w the t stat. First thought it was my water pump electrical connector since the pins on my pump I replaced seemed to have been burnt through so I was thinkin connectors prolly ducked as well. Spliced on new connector but nope waterpump dont even run at all. Man these cars are a pita I've given up and will be takin it to a workshop tomorrow. I'd love to help but man the amount of changes bmw has made with these fuses is ridiculous to sort through and when it gets this complicated I'd rather just give it to a shop at this point tbh. Good luck lmk how urs goes����

Haven't updated in a fat minute but turns out the diode in the pump blew. After only like 2k miles too. I honestly didn't expect it but it was the easiest solution. If it doesn't drain then probably not a short. I would check if the 12v continuous power is going to the pump. If your battery connection to that is corroded the pump wouldn't power on. From my long research around the fuse revisions, regardless of what year the big fuse in the DME for the 335i regardless of 40a or 50a will be the fuse for the water pump's direct current power from the battery. I would take a voltmeter there and check for 12v. Good luck. Now I've got to deal with a dead headlight but I still love driving the car when it does work. But definitely a PITA to keep them error free. So far about 1.5k in and longest it went without a problem was 7 months

For a test on the water pump's electronics: take a multimeter with continuity/diode tester function and put the ground lead of the multimeter to the ground pin(big pin on bottom right w/ the clip on top or the pin the thick orangish brown cable connects to from the connector) and test with all the other three pins. There should be no current flow. If there is, something is shorted or blown. MAKE SURE TO PUT THE GROUND LEAD TO THE GROUND PIN. There are diodes in the water pump so putting the negative lead on the ground pin will present continuity with some pins. You should also check the connectors. There is a voltage reading the connector should give when battery is connected somewhere on this forum.

[Valentinmew]

[/QUOTE]
, http://onxx.ru/

[KeesM]

Originally Posted by Hottie335

Same bro I have a similar issue except my battery doesn't seem to drain but pump doesnt run at all. Codes 2e84 water pump missing even tho replaced it twice along w the t stat. First thought it was my water pump electrical connector since the pins on my pump I replaced seemed to have been burnt through so I was thinkin connectors prolly ducked as well. Spliced on new connector but nope waterpump dont even run at all. Man these cars are a pita I've given up and will be takin it to a workshop tomorrow. I'd love to help but man the amount of changes bmw has made with these fuses is ridiculous to sort through and when it gets this complicated I'd rather just give it to a shop at this point tbh. Good luck lmk how urs goes👍🏽

Hey Hottie335, did you have any results with your problem? Got exactly the same issue as you do. Hope that you can help me in some way.

Kees