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Persistent Camshaft Position Sensor Faults? READ THIS!
P0392 Camshaft Position Sensor B Circuit Low Output (Bank 2) P0024 Exhaust Camshaft Position Timing Over-Advanced (Bank 2) Knowing that going in, I ordered new CPS all-around and proceeded to replacing the VCGs. Bank 1 (right) first as access was better, lots of experimenting with the Valvetronic motors (mine had no way to turn the shaft nor a plug to access the hex screw everyone says is there, totally sealed unit which I had no intention of drilling a hole in); even though mine “popped” as it was coming out, it stopped while going back in at the same place, so simply pressing it in while putting in the first hex screw returned the Valvetronic gear to exactly the same position it started in. So don’t panic when the motor pops out and DON’T screw it back in as often suggested, just push it down. Note that the Valvetronic equipped engines have all 4 Camshaft Position Sensors at the REAR of the plastic valve covers, the upper is Intake and the lower Exhaust on each side. This is not mentioned at all in the X5 Bentley manual and is key to this fix! Anyway, after completing & buttoning up Bank 1 (new plugs, both CPS replaced), I moved on to disassembling Bank 2 (left) which IMO was considerably more complex. Had to remove fuel rail, heater hoses, battery cable as well as the Valvetronic motor and then was able to barely maneuver it out. While wiping off the head flange, I heard a metal tinkling noise when I reached the rear of the exhaust (lower) camshaft and realized the reluctor (the metal piece that the camshaft sensor “reads” which mounts on the end of the camshaft) was TOTALLY LOOSE, and spinning freely! The nut that’s supposed to hold it in place was laying in the head, fortunately it’s a bit larger than the oil galleries so it didn’t fall into the engine. So basically, what the CPS was reading was just randomly bouncing around (or not moving at all) so it had no reference whatsoever. I panicked for a moment wondering how the reluctor was supposed to go back on but fortunately it has a keyway which fits a slot in the end of the camshaft. I took it all out, cleaned it up & reinstalled it with Loctite Red on the nut, which has a hex head, tightening it up as much as possible. The key was kind of beat-up, probably as a result of bouncing around, but still usable and the piece went back on just fine. Voila, no more CPS faults! In 45+ years of working on vehicles I’ve never seen nor heard this mentioned as a cause of CPS faults and had I not lucked into it I’d have probably chased all the other possibilities without any luck whatsoever. So if you’ve been trying to trace CPS failures by replacing & swapping sensors, checking wiring, etc etc etc without any success, take a look to see if your reluctor has come loose. You can check it by simply pulling the CPS and using a screwdriver to see if the reluctor is rotating freely or perhaps has even fallen off the camshaft. You definitely have to remove the valve cover if that’s the case. I went back and checked- all the cams are the same design, so the reluctor could potentially come off any of them. Hoping this helps get a few BMWs back on the road which are sidelined by the most obscure fault ever! Sorry for no pics but am new to the forum and have to get my filesizes down. Coming soon... |
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#2
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Use tapatallk to auto resize photos.
Wow so the N64 has indexed rekuctors that takes all the "fun" out of setting timing. Sent from my iPhone using Tapatalk Pro
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#3
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Here’s the reluctor on my workbench, and safely back where it belongs.
RealOEM confirms the presence (and name) of the reluctors...that’s what they are called with other Hall Effect type sensor systems (ABS, solid state distributors) but frankly I’m a little surprised BMW uses the same nomeclature...you’d think it would be some 25 letter unpronouncable tech term! |
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It's so very different than the m62 stamped metal. Thanks for sharing. I'm curious how is the timing set of the reluctor is keyed? Count the chain teeth?
Sent from my iPhone using Tapatalk Pro
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#5
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Because it’s at the rear of the cam, which has a slot for it to fit into, it seems that the reluctor position is literally built-in to the engine design. The programming map for such a sensor would simply be a series of high/low voltages read by the CPS which correspond to the 360 degree cycle of the cam. No messing with it, no counting teeth and unless the key on the reluctor is totally destroyed, no getting it in wrong.
Yes, the plastic valve cover is totally different and it's clear BMW simply changed the design for the Valvetronic engines without regard to accessibility for maintenance. Getting them off is extremely complex, with the Eccentric Shaft Sensor being the biggest PITA - it’s located at the rear of the Valvetronic shaft and is quite tall (and stupid expensive) so even after everything is loose you have to maneuver the valve cover up & over it without snapping off the rather fragile locking tabs. On Bank 1 I had to remove the plastic “wall” on top of the strut tower for clearance, and very slightly bend the AC line out of the way; would’ve done that on Bank 2 also but the entire wiper assembly would’ve had to come out. Probably easier to cut a slot in that side plastic wall to give the CPS clearance to lift off the valve cover! |
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Some days I'm quite happy I accidentally ended up with the M54. I love the tech of the N64 n52 but yikes when the valvetronic takes a shit
Sent from my iPhone using Tapatalk Pro
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#7
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Duh on the reluctor position. I was thinking the reluctor ometer was measuring the outside of the vanos but that doesn't make sense. Thanks for inadvertently seeing me straight
Sent from my iPhone using Tapatalk Pro
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#8
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My wife’s X5 has the M54 and it’s a breeze to work on. Had the VCG changed in her car in under 2 hours start to finish. Took me that long just to start figuring out what to remove to get my VCs off!
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camshaft position sensor, cps fault, eccentric shaft, m62, valvetronic |
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