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      06-22-2019, 08:46 PM   #1

Drives: 2011 BMW 335xi
Join Date: Jun 2019
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Diagnostics Nightmare in K-Can Low Line (2004 545i N62 Automatic)

This has been a bit of a wild ride, so i'll try to leave out the unnecessary data.

Currently assisting with diagnostics and repairs on a '04 545i.

Prod. Date - 2004-02-03
Type - 545I (USA)
Series - E60 (5 Series)
Body Type - LIM
Steering - Left Hand Drive
Engine - N62
Displacement - 4.40
Power - 245kw / 333hp
Drive - HECK
Transmission - Automatic

Last known mileage is 289887 km / 180127 miles per ISTA, from a scan approx 1 month ago. So, not TOO far over that.

Initial issue presented as Parasitic draw, moderate to high volume. Owner believed issue was due to new battery being installed but not properly coded. Coded module to provided specs of new battery, conducted ISTA scan.

Initial ISTA scan from 23MAY indicated K-Can line faults as follows. Cleared not currently present faults:
0x00D904: CAS: K-CAN line fault
0x00D9C4: MPM: K-CAN line fault
0x00DA04: SHD: K-CAN line fault
0x00E204: PDC: K-CAN-Low wire fault
0x00E244: SZM: K-CAN line fault
0x00E2C4: CON: K-CAN line fault
0x00E444: SMFA: K-CAN line fault
0x00E484: SMBF: K-CAN line fault
0x00E504: LM: K-CAN line fault
0x00E584: KBM: K-CAN Line fault

PDC had a low wire fault, began testing there. Didn't have the right size probes to fit inside the harness, and was unable to test total voltage or resistance between K-Can High and Low lines.

Moving onto today:

After prior meetup, battery could not gain any charge on a 2A trickle charger that I provided. Per my recommendation, Owner upgraded to a 2/15/50A charger to mitigate until a further time for me to complete more diagnostics. For the last month since upgrading to 15A charger, owner has had minimal issues with car starting in morning, but parasitic draw has increased in level, with vehicle now barely being able to start after 10hrs of sitting while owner is at work.

(Note: This is not a job for me, this is a hobby. A masochistic nightmare of a hobby on top of 40hrs of work and 20hrs of school a week. Thus, the month between diagnostics.)

Owner informs me of new issue, CCC unit has turned off, completely black screen. Was not able to recover with a standard CCC button-hold reset. Fuse F34 (30A) in glovebox was not blown. (Honestly, I just hoped that the CCC module wasn't fried, or i'd have been pulling the old CCC modules out of an '07 530i in a junkyard, and reprogramming. FML.)

Focusing diagnostics on the K-Can line with the right size probes, began disconnecting modules one at a time, testing voltage and resistance, and then running ISTA scan to see if faults stopped repeating.

Total voltage between K-Can High and K-Can Low was .36v, expected was 5v. Discovered that K-Can Low was not reading any voltage when connected Low to Ground. (Expected values were 4.6 on low and .4 on high, OR sum of both lines being 5v for rule of thumb.)

Disconnected CAS (Or Gateway, I can't remember anymore), Ran ISTA scan (No connection, expected), reconnected CAS. CCC unit comes back on when car is started after CAS (or Gateway) was reconnected.

*Confusion intensifies*

Tested ALL modules on K-Can line that I could get to (No Sunroof or anything not in the cabin or trunk). MPM was dry, no water ingress. All K-Can wires leading to modules are reading .4v and open line for resistance. No frayed wires at common points of fraying (In trunk/Driver footwell/Passenger footwell). With exception of seat modules.

*Something is very wrong here*

Tested K-Can lines leading to BOTH seat modules, total voltage on High and Low lines is 11.5v. Maximum expected was 5v. I checked my pinouts, wire colors, and leads THREE TIMES. No change. I don't think I remembered to test for resistance, due to being absolutely completely stunned.

Both the Driver and Passenger seat lines are reading at 11.5v between K-Can High and Low. I KNOW this is wrong. Prior errors on ISTA scans showed Undervoltage AND Overvoltage issues on some modules. Because they were not currently present, I thought it was due to the battery drain or something. They also didn't come back when I cleared them and ran the engine.

Here's what I think is happening. The K-Can Low line is broken at a point between the harness/modules under the passenger side footwell, which is why i'm getting Open Line resistance at every other module. If that wire is touching any other source of voltage (or even another frayed/cut/fused wire), the shortest path of resistance is going to be in that area.

So, my question is, does anyone have an actual "This is where the wire is routed" path for the K-Can line? Or what the actual "path" is? Because isn't good enough. Both of the seat modules curve towards the center console, and either go to the undercarriage, or under the console. No idea where to start looking, and the "wiring diagrams" say that the MPM in the trunk is directly connected in parallel right next to the Passenger seat. So i'm... skeptical.

Last edited by Zearkos; 06-22-2019 at 09:11 PM.. Reason: Missed a few lines, moved some things around.
Appreciate 0
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