Need help troubleshooting Comfort Access

doru · 10-13-2015, 07:57 PM

I purchased the car not too long ago (2011 335is) and the comfort access didn't work since day 1 I purchased it.
Now I want to make it work, so i hooked ISTAD and I have the following code: S0159: "No communication possible with comfort access"
ISTAD also prompted that: "Junction box A4010 (glove compartment fuse box) has deactivated relay terminal 30g-f"
Now I started first by checking the fuses, and I found fuse #61 toast (5Amp).

I replaced the fuse so as to be able to maybe go a step further with my ISTAD diagnostic, but it was the same message. I checked the fuse #61 again, and it was again toasted. So I have a short somewhere I believe.

Not sure where to start. I looked up the diagrams in Bentley, but when it comes to electrical & electronic stuff, I'm not the best, as opposed to mechanical skills (not the best either probably, but my BMW's were serviced strictly by me for quite some time now).

I would really appreciate some hints, head-ups or any help.

Thanks

lobotomy · 10-28-2015, 06:54 PM

does the diagram in Bentley show fuse 61 circuit? (I am not familiar with Bentley)! Does the fuse pop as soon as it is installed? one leg of that fuse is shorted to ground.
TWO heads up I can give you:
1).This is where you need to be careful, NO test lights can be used to diagnose.
2). Never install a higher amp fuse then what is called for when diagnosing/repairing!

Generically speaking, and this does not apply to your case because I do not know the particular circuit, I check both sides of the fuse circuit with a LOW impedence DVOM to check present voltage. Do this with the fuse removed. One side should be + voltage (source). I measure this by placing DVOM to voltage (DC) setting, then one lead to fuse tab & the other to a good ground. Once I identify the source side, I move over to the other prong, which is the load side, and very likely my problem side. I verify this side is shorted to ground using the DVOM. If I can easily trace the circuit back to the endpoint (load) & disconnect it a that point, do so & then re-check at fuse block again to see if short disappears. At this point, if short still exists, using a schematic, I trace the problem wire via the circuit schematic to a midpoint, somewhere I can access easily, preferably at a connector. I then isolate the wire in that circuit at that point, and check both sides to see which is shorted. I do this until I find the source of the short. That's the "basics" I use to diagnose. It is not specifically applicable to you because you need to know the circuit schematic to be sure it applies! These are complicated circuits involving modules & communicating buses, so even basic checks must be approached with caution, and may not be applicable!

10-13-2015, 07:57 PM	#1
doru Lieutenant 126 Rep 482 Posts Drives: e92, f25, e46, e83 Join Date: May 2015 Location: Calgary iTrader: (0)	Need help troubleshooting Comfort Access I purchased the car not too long ago (2011 335is) and the comfort access didn't work since day 1 I purchased it. Now I want to make it work, so i hooked ISTAD and I have the following code: S0159: "No communication possible with comfort access" ISTAD also prompted that: "Junction box A4010 (glove compartment fuse box) has deactivated relay terminal 30g-f" Now I started first by checking the fuses, and I found fuse #61 toast (5Amp). I replaced the fuse so as to be able to maybe go a step further with my ISTAD diagnostic, but it was the same message. I checked the fuse #61 again, and it was again toasted. So I have a short somewhere I believe. Not sure where to start. I looked up the diagrams in Bentley, but when it comes to electrical & electronic stuff, I'm not the best, as opposed to mechanical skills (not the best either probably, but my BMW's were serviced strictly by me for quite some time now). I would really appreciate some hints, head-ups or any help. Thanks __________________ Stable: e92is f25 N52 e83 N52 e46ci M54B25 (e53 N62 - sold, R.I.P. e39 M54B30)
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10-28-2015, 06:54 PM	#2
lobotomy Private 26 Rep 68 Posts Drives: 2011 328xi Join Date: Aug 2010 Location: NY iTrader: (0)	does the diagram in Bentley show fuse 61 circuit? (I am not familiar with Bentley)! Does the fuse pop as soon as it is installed? one leg of that fuse is shorted to ground. TWO heads up I can give you: 1).This is where you need to be careful, NO test lights can be used to diagnose. 2). Never install a higher amp fuse then what is called for when diagnosing/repairing! Generically speaking, and this does not apply to your case because I do not know the particular circuit, I check both sides of the fuse circuit with a LOW impedence DVOM to check present voltage. Do this with the fuse removed. One side should be + voltage (source). I measure this by placing DVOM to voltage (DC) setting, then one lead to fuse tab & the other to a good ground. Once I identify the source side, I move over to the other prong, which is the load side, and very likely my problem side. I verify this side is shorted to ground using the DVOM. If I can easily trace the circuit back to the endpoint (load) & disconnect it a that point, do so & then re-check at fuse block again to see if short disappears. At this point, if short still exists, using a schematic, I trace the problem wire via the circuit schematic to a midpoint, somewhere I can access easily, preferably at a connector. I then isolate the wire in that circuit at that point, and check both sides to see which is shorted. I do this until I find the source of the short. That's the "basics" I use to diagnose. It is not specifically applicable to you because you need to know the circuit schematic to be sure it applies! These are complicated circuits involving modules & communicating buses, so even basic checks must be approached with caution, and may not be applicable!
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