Hello all, I bought a 2000 540i nonrunning(i know.., I know...) The previous owner took it to the dealership and decided he didn't want to put anymore money into it. The dealership found that it needed all sparkplugs, 1 ignition coil, thermostat, and new battery. Now it wouldn't start, they narrowed it down to the fact that the DME was not responding. "many modules had communications with the DME". The last thing they said was that they needed to "perform wire testing for power supply to DME". I asked a mechanic later and they verified it was getting power. When you plug a OBDII reader it wont make any communication. I'm leaning towards the DME being dead. i pulled it and it looks clean with no obvious coolant damage from the Thermostat. I have bought and replaced the battery. I have all the spark plugs and thermostat and ignittion coil but wanted to install it after I figured out why the DME wouldnt even acknowledge. A new one is 2000 from BMW and there are services online for 250 that repair bad ones. has anybody seen this before? Any help would be much appreciated.
Well this could get kinda complicated quickly. If the DME is not communicating properly and the power and grounds are good to the DME the last thing you need to check is the Communication system of the DME. If the DME can't communicate then it makes it hard to diag the real issue since you can't get faults. Does the vehicle crank but not start?
Thanks for the reply! So yes it cranks but doesnt start. There is no coms from the DME which the dealer verified. I read on a forum that sometimes when a thermostat goes bad(mine is bad) that the coolant can travel up to the DME and corrode it. However, i pulled the DME and it looks clean. A mechanic came by and told me to start with a new battery which I did but no difference. I really wanted to verify that the DME was getting power but didnt know where to chk. The mechanic said he verified it already but I just wanted to check. would anything else stop it from communicating?(ews?) btw, I hope to eventually move up to the awesome M5 you have!
Besides checking the power and grounds for the DME you will need to check the communication lines for the DME. These are used for the DME to talk to the other modules and to communicate with the scan tool as well. If any of these lines are not working you can't talk to the DME but the DME may be working normally still. If the vehicle cranks I have two other suggestions one is you may have a bad ignition switch causing all your problems they do really weird things when they fail. The other would be to do a EWS to DME rolling code alignment. But since you can't talk to the DME that won't work. Thanks I do enjoy my M5 quite a bit.
Hello again, sorry it took me so long to reply. I sent out my DME along with key and EWS to get checked/fixed as I thought since I was getting communication errors with the DME and no codes or communication with OBD2 that it was most likely bad. I also checked the power coming in which was good as well. The DME service said they found : 04/08/2015 5:49:25 PM Tested - No coils or injectors fired. Rebuild - Both main processors and replaced blown chip. Inspection - PCB check for water damage and broken traces. Post-Test - Injectors and coils fired as they should. Repaired and warrantied. So I thought, slam dunk , lets put it back an go. But still same problem the engine cranks and turns over but no start. There is no spark and no injector signal. Verified power going to the DME and input voltage coming in on the signal wire. My mechanic hooked up his computer to the Round connector in the engine bay and was not able to communicate with the DME. But he found that other modules had "can errors, trying to communicate with the DME".His advice was that the DME was still bad. I also read several things that could cause no codes from the OBD2. One person said the fuse box under the passenger seat was flooded and corroded and that dropped the voltage which among other things caused him to get no readings from the DME. So , i removed the passenger seat got to the fuse box and found it also was sitting in 1/4 inch of water which I cleaned up but it didnt seem to touch anything significant. Again I got no response from the DME. And lastly, a mechanic on a another forum said he had a 2000 540i like mine came in and had no codes. He traced things to a bad ABS module, which when he unplugged, all of a sudden he had communication with the DME. I also tried this but no success. My next step is to test the crankshaft sensors as these are input signals to the DME necessary(ive been told) to start spark and fuel. If That doesnt work, I will call the DME repair place and tell them its still broken. Do you still suggest I check the ignition switch? Super thanks for your help
Ignition switch can cause weird issues and yes should be check or better yet swapped from a known good car. Very easy to do and a quick check. The other thing is to check the Communication wires to the DME depending on the production they can differ a bit so look at a wiring diagram. Make sure your getting proper voltage on those wires. The line should be called either TXD or RXD if I remember correctly. You can also scope this signal at the DME and see what kinda pattern your getting should be a nice square wave. If you don't then you have a issue with the module or wiring or another module bringing the network down (your ABS module story is exactly that. Have you done a EWS to DME alignment after the repairs?
So since I don't have access to a known good one(ignition switch), I guess I need to buy one and just try it?(hate to waste money)? I'm not into shotgunning parts but if that is a reasonable thing at this point I will try. Our stupid scope has crapped out so at this point I will have to find one. As for your question of the EWS and DME alignment, in your earlier post you had mentioned that since I have no coms with the DME , I will not be able to do so, correct? I assumed that since I sent in my DME for repair and they asked for my EWS and key to be sent with it, that they bench tested them all together and therefore the new alignment would not be necessary. I am going to write to them anyway and explain that I still can't communicate with it and other modules are having communication errors with it. BTW, there is a popular "what to do if my BMW wont start guide" , that I have followed and it directs me to the next step of checking the crank and cam positioning sensor which supposedly gives an input to the DME before it can give spark and fuel. But would that also cause no readings from the DME? Thanks again, I'm sure it's a pain dealing with numbnuts like me but your help is much appreciated!
Just because you don't have a scope doesn't mean you still can't check the CAN system to the DME. You just need to check for voltage on the high and low CAN wires. If the voltage is in spec should be some where around 5v then you know communication is possible on those communication lines and probably are not the issue. If they don't have the voltage then you would unplug the modules on the Bus system one at a time and check if the voltage come back then that module was causing Bus communication problems and you should recheck to DME communication. I also don't recommend just throwing parts if you don't have one to swap for the ignition switch the other thing option would be have advance or oreilly get you one and if it doesn't fix anything just return it. The crankshaft sensor and the camshaft sensors are used for enabling fuel and spark but if the crank sensor fails the engine can still start using the camshaft sensors and a longer crank. Sorry I misread that you sent the EWS with the DME yes they should have done the EWS to DME rolling code alignment. Does that company that rebuilt the DME test for CAN communications?
Sorry for not replying sooner, work has been hectic! So recently I found a 2003 540i that was parting out. I was able to get a matching dme,ews, key,key ignition. I installed them and the car started right up and was able to read codes and have communication with the obd2. So to me that means the CAN Bus system is healthy and the issue lies somewhere with the dme. Now I just had my original dme repaired and sent my ews and keys with it. They said it was tested but I when I got it back and installed it there was no change and still no communication with the other modules(instrument cluster). Is this an alignment issue with the dme/ews? Would that cause there to be no communication with other modules or obd2? I would like to use my original equipment but I'm not sure where the problem lies with it. I think my next play is to send it back to the repair service and have them fix it again. What's your idea? Btw......after I installed the other dme set and it started up, when I heard the engine it sounded soo sweet! Can't wait to get this thing on the road!
Yah I would have them test it again for communication issues and since you will have to send the EWS then can make sure it is aligned and working.
Hey Charlson89, Thanks again for all your help. So to recap what has happened quickly: My original DME had no communication. I sent it out to be fixed but still had the same issue. I found a totaled 540i and took the dme/ews/and keys /ignition and swapped them. The car started immediately. So I resent the original DME,EWS/keys to the ECU repair service again and this time they confirmed they had no communication with the dme and couldn't fix it either. So as I see it I have two options. 1)Send the dme to another service that is more expensive and specializes in BMW DME's that says they can fix it (650usd) and sell the DME/EWS /Keys & ignition I got out of a totalled 540i to try and recoup some of the money I spent on the DME repair or.. 2)Go back to the totalled 540i and remove the doorlocks(cylinder only?) for the doors and trunk and also the alarm "module?" that would be mated to the keyset for opening and closing the doors with the remote. *Please correct any assumptions I have made for this option. the keys from the totalled 540i are not able to activate the doors which i believe to be because they are synched with a for lack of better term the original "alarm module". I am also assuming it is possible and easy to remove the key locks for the other car and replace them myself. Current condition: runs great with the dem/ews/keys from the donor bmw. I am just unable to lock the doors and use the key functions with the the car as they don't match. When i bring the old keys in proximity and try to use both sets, one for ignition and one for the doors, the car alarm starts and all sorts of crazy issue ensue. thanks again for the expert opinion!
Ok so only issue I see with option 2 is if you do that yes everything will swap over and like you said run. But you will run into issues with diagnosis on the vehicle since the vins in the modules will not align with other ones in the vehicle. This can cause confusion on something stored in the vehicle called a VO (vehicle order). A VO is basically a electronic list of what options and coding the vehicle has. Thus a different vehicle can have different options and coding. Not to say this is a big deal just want you to be aware of it. Personally I would send my DME out for repair to a specialty shop and sell the others if they can guarantee a repair for your money. And why can't the other repair shop give you your money back they didn't repair it?
Hmm, I didn't know about this Vehicle Order before. So basically the other modules(on the can bus maybe?) will eventually have a conflict because the vins and options don't match? So then i guess I will try to contact a bew company to see if they can repair my original dme. Also, the other company that attempted twice to fix my dme did refund me completely(thankfully). Thanks again for the advice. i will report back on how things go.
