pgnuta 4 Report post Posted January 15, 2017 Hi Folks, i'm back for round two. My 540i e39 has always had a voltage slow leak which culminated a couple of weeks ago with my battery needing to be replaced finally. Since then i've had intermittent issues starting the car, especially when its hot. Ie if i start it cold in the garage in the morning it runs fine but if i drive it to the shops then its almost guaranteed to not start a second time. Most of the time if i hold the key in the crank position it will eventually crank over and start and run like normal. Just to be clear, when it doesn't start it doesn't do anything... No sound, no click from the starter solenoid, no crank, just normal lights on the dash. So it carried on like this for a week or two until this week when it began not starting at all, even when cold. I noticed that if it failed to turn over then you couldn't move the key to the start position a second time which i presume is a failsafe and quite normal. I also noticed that no matter how long i held the key in the start position nothing would happen, well not quite... After about 30 seconds the lights on the dash (the park brake light and others) would start to dim and flash randomly, also the temperature gauge would be off the gauge on the hot side, a few more seconds and the engine failsafe message would come up on the display, sometimes after this the car would start and run normally but generally not. If i turned the key to the ignition 2 state and left it there it would do the same thing with engine failsafe normally. So i decided to get my laptop with INPA back from a friend it had been lent to and proceeded to check the codes etc. I cleared all the codes and adaptations and let it relearn everything, started the car once and gave it a few minutes to warm up and idle down and a few good revs and switched it off, then it was back to its same old tricks of not starting. To compound the problems it seemed that while it was in that initial 30 second initiation phase INPA couldn't read anything from the computer and it took me several tries to get the error codes out of it but i finally was able to extract one concise error: Date: 01/15/17 13:10:36 ECU: ME72KWP0 JobStatus: OKAY Variant: ME72KWP0 ------------------------------------------------------------- RESULT: 1 errors in error memory ! ------------------------------------------------------------- 136 Test emergency air position Error frequency : 1 Logistic counter: 40 Supply voltage 12.53 V Intake air temperature 28.50 Grd C wdknlp 15.69 % Setpoint DK-angle at NLP-position 15.68 % DK So i did some googling and found a lot of conflicting arguments, some people said it was a MAF problem, some people said it was a throttle body problem, i tried unplugging the MAF and it started a couple of times but i've just gone out now to try starting it again and its doing the same thing even with the MAF unplugged so probably a red herring. I'm probably going to try unplugging the battery for a few minutes and double checking the battery leads are good and tight and free from corrosion. I also need to check the main computer loom plug for moisture but i don't know where that is. So i guess i'm stumped at the moment, if someone can give me a hand i would greatly appreciate it Quote Share this post Link to post Share on other sites
kiwi535 538 Report post Posted January 15, 2017 i beleive ignition switches are a fairly common problems on e 39s? Quote Share this post Link to post Share on other sites
pgnuta 4 Report post Posted January 15, 2017 I might be clutching at straws here but in reference to the common boot lid loom wear problem with these cars i have observed that after opening the boot the car starts. This might also be a red herring. Trouble is that last time i checked this i pulled the protective rubber cover back from the wires as far as i could but didn't see any worn or broken wires. Is it true that to properly check this i need to completely cut off the rubber boot? Quote Share this post Link to post Share on other sites
allan 295 Report post Posted January 15, 2017 If you suspect the ignition switch try this test. You don't need to cut the rubber protection at all just peel it back. Their will be little to see unless the outer cover of the wiring has been damaged what happens is with the action of opening and closing the boot the copper wire filaments work harden then brake. This creates an open circuit and all sorts of weird things will happen. These wires need to be tested then the faulty one's , if any removed / repaired problem solved. It is a pain but welcome to the problem world of e39 owner ship best of luck. Quote Share this post Link to post Share on other sites
