Hey guys, first thank you to everyone who posts here. I use this information frequently to diagnose and fix problems.

I recently have had several issues arise on my 2004 E60 545i with the N62 engine at 123k miles. Every once in a while, no matter the length of a stop, will not start. The lights come on, but the engine won't crank at all. Sometimes it starts after attempting 5 times, sometimes it takes 30 times. I sit there and turn the ignition off, then on, then off, then on until it starts. Once it starts, it's a normal start with no hesitations. It sounds like the starter is on it's way out, but I need to confirm before tackling that job. I've also read the CAS, Integrated Supply Module , or some other module might be the issue. Thoughts?

Also recently, I was driving and the car felt like it died, the RPM's dropped, lost power for an instant, and then it drove rough until I was home. It through a CEL and showed crankshaft position sensor and E-box fan among others that were probably a result of the crankshaft position sensor. I just replaced the crankshaft position sensor last year, but upon further reading, have found individuals with the same issue. It turns out the insulation around the CPS plug is getting so hot that the insulation starts cracking off and the wires start touching. I did order a new E-box fan which will be installed upon receipt, and I'll check the CPS plug wires for damage.

Thanks guys!

 

The cuprit could be the alternator. Maybe, it is not charging your battery sufficently. A weak battery and not charging alternator can cause all kinds of electrical malfunctions.

 

Good idea, but I replaced the alternator earlier this year.

 

If you have not done so "RECENTLY", you should test the alternator, battery and IBS before you start replacing other parts.

 

How about battery ? If the alt. and bat. are not on the same page it causes all kinds of electrical hell . It will throw every light/code on the dash. I had this happen a few months back and warnings galore went off .

 

Funny, I have same issue on same vehicle... 04 545 6sp with 78k.

So far I have read that the crank sensor might be the culprit or the clutch sensor/"neutral switch", the starter, the Integrated Power Supply, the battery, the alternator... No error codes given. In my case, battery is fully charged with "trickle" charger. Someone out there must have had the same issue and has the answer!

 

What is the electrical circuit equivalent of "not on the same page"?

Battery? I doubt it. If you turn the key 30 times and it doesn't start because the battery can't deliver enough amperage, what suddenly "energizes" the battery on the 31st attempt?

A bad alternator may not charge a battery, and it may deliver an over-voltage to the electrical system after starting, but it will not prevent a car from starting if the battery has sufficient voltage.

OP - Your phrase "every once in a while" leads me to believe that this intermittent problem (that comes and goes) may be due to a worn component making a poor connection.

But to just eliminate the battery/alternator get a plug-in volt meter. Leave it plugged in and monitor your voltage constantly. Monitor before starting (turn key to on position but don't crank the engine - you want to see 12.1-12.5V) . Then start it and watch the voltmeter for the first 30-40 seconds after starting (you want to see 12v ramp up to about 14.2v) . Then glance at it occasionally during driving (should vary between 13.5V-14.5V).

If you see numbers close to these then start thinking about the starter solenoid. When it won't start have someone else get in the car and try to start it while you have an ear as close as you can get to the starter. If you don't hear a click when the key is turned that means one of two things - The starter solenoid is not engaging when a voltage is sent to it (solenoid on the starter is going bad) or the voltage is never being sent to the solenoid in the first place. If you hear a click but the engine won't crank then you are done troubleshooting - it is the starter motor starting to fail and the starter needs to be replaced. Unfortunately for the E60s the starter placement is such that it is not easy to attach a set of voltmeter leads to the solenoid to see if it is getting voltage when you turn the key.

Intermittent ground connections can also be the source of starting gremlins, although unless you have had recent work done on the car, especially body work or electrical system work, this is less likely.

If you don't hear the click you can also temporarily assume the solenoid is good and try to work upstream. In your case this is not a bad assumption as the solenoid is a coil that acts as an electromagnet. When voltage is applied the solenoid pushes a plunger to engage a starting gear into the engine and closes a circuit to apply voltage to the starter motor itself. Generally if the solenoid is failing but continues to start after multiple attempts, it gets weaker and weaker over a period of months until one day you get nothing, whether you turn the key 10 times or 1000 times. But from your description you can go days with no symptoms.

Keep picking away at all of the things that prevent a voltage from being sent to the solenoid. One example is the switch associated with the brake pedal. If the switch is worn and the computer thinks you are not pressing the brake pedal because the switch is not closing the car won't start. A second example is a worn ignition switch with the contactors needing to be in just the right position before a connection is made. Electronic modules can certainly prevent starting but do not generally come and go as you describe.

Intermittent starting can be as frustrating as a vacuum leak. But stay with it and keep eliminating possibilities and you will eventually arrive at the cause.

 

Thanks! I believe the last time it happened (this is the third occasion), I did pay attention and noticed a single clicking sound; although hard to tell where it was coming from since doors and windows were closed. I will take your recommendations!

 

Actually I wasn't on the same page because I was on multitask overload . BUT my car went haywire all lights came on it would click and click then nothing wait 15 min then do it again and I was stranded at a rest stop . Then finally started .U got home and alt was just giving enough to run and battery was shot but acted like it wasn't . So I might not have been on the same page at the moment but my answer wasn't far off base since the electrical systems in these cars do some unexplainable and screwy shit at times.

 

+1
You are right about that. BMWs can act like they have lost their minds when the electrical system acts up.

The ECU has some interesting self-protection characteristics when the battery voltage sags. Electrically, when a device demands power but the voltage sags low, the device draws more current to maintain the same power ( Power = Voltage X Current).

A significant increase in current can begin to overheat wiring and circuits. So the ECU begins to shed load by turning off power to non-critical systems in the car when the voltage sags below a certain minimum. Some of the non-critical systems are things like transmission control, active steering, and certain lighting systems in an effort to keep total current draw below a safe maximum. Hence the Christmas Tree effect on the dash when the battery begins to fail or the alternator begins to fail, which then leads to battery undervoltage.

In my case the voltage regulator went bad and started pumping high: 17V on start up. You should have seen the fault lights then. Every system screamed at the over-voltage.