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Thread: Cam Position Sensor (CPS) Fault

  1. #1
    Administrator thegunguy's Avatar
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    Cam Position Sensor (CPS) Fault

    I'm working on tracing a SES fault on the car that showed up and went out last week. Reading the codes on the iPhone show it to be the Cam Position Sensor. I did some reading on the M5board.com, and these are pretty common maintenance items, but I don't recall any documentation here. On the M5, they're pretty easy to service in your garage. So, that's likely what I'll do and report back here. I've sent the codes off to Dana to confirm.

    More to come...

    FYI - Loving Rev2 and the Kiwi ODBII reader for the iPhone. Can't wait to play with it on the iPad.
    thegunguy

  2. #2
    Administrator thegunguy's Avatar
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    I just got a call from Matt Carver, the Z8 guru at Peter Pan BMW, and he confirmed my diagnosis on the Cam Position Sensor. As many of you know the VANOS system the camshafts in different settings based environmental, fuel, and performance inputs. These sensors keep track of the positioning of the camshaft.

    Matt confirmed that these sensors are a common maintenance piece. Overtime they just get gunked up, etc. and become unreliable. When they fail, the computer sets the camshaft to an average position. So, a failed sensor is not a critical engine event, but the engine will not run optimized to its environment or perform to it's maximum capabilities, until the sensor is replaced.

    Matt also confirmed my research that the sensors are fairly easy to replace, even-though they may require some contorted hand positioning. The sensors are held in by a 5mm allen bolt(s) (to be confirmed), and the procedure requires replacing an o-ring as well.

    I plan to order the new sensor in the next day or so. Looking at realoem.com, I believe the part is listed as 'Pulse Generator, Camshaft', under the Engine>Ignition System. There are different parts for intake and exhaust sides. Looks like they'll run about $100 a piece.
    thegunguy

  3. #3
    My first CP sensor (L-exhaust) expired at 50k miles on the E39 M5 daily driver. I replaced it myself. Within a thousand miles, two more sensors expired, so I did those as well along with the fourth. My experience was consistent with that of other users on the M5 board in that once one sensor goes, the rest tend to follow shortly thereafter.

    When the first one expired at 14k miles on the Z8 (coincidentally, also L-exhaust), I had the shop replace all four CP sensors at once. The engine bay of the Z8 is a little tighter than the M5, and replacing the M5's wasn't such a walk in the park.

    Since then, and still around 14k miles, both Throttle Position Sensors on the Z8 have also been replaced. No trouble with those on the M5 yet.

    Tyler

  4. #4
    Administrator thegunguy's Avatar
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    Finally tackled this one today. It's a fairly easy operation other than the tight access to the sensors at the back of the engine. I only replaced the faulty sensor, but I did get familiar with the other three for the inevitable future replacement, and the passenger exhaust sensor (the one I replaced) is most certainly the easiest.

    Here are a few threads from the M5 guys that I used for reference. I couldn't begin to do a better job documenting than some of these guys.

    http://www.thestebbins.com/Michael/b...placement.html
    http://www.m5board.com/vbulletin/e39...cyl-5-8-a.html
    http://www.m5board.com/vbulletin/e39...on-sensor.html

    The one thing I can add is that I love my stubby 3/8" articulating ratchet. If you plan on doing this repair, you might want to grab one. It really helps you get maximum rotation in the cramped space.

    I paid $140 for the sensor after CCA discount, and it took me about an hour to complete.

    Andrew, since this is a very common issue with the S62, this might make a good sticky.
    thegunguy

  5. #5
    Z8 Addict Scott Pettit's Avatar
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    At Bavarian Auto they are $115.95. Hate to tell ya.
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    Administrator thegunguy's Avatar
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    Congrats. You win.
    thegunguy

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    I replaced a left exhaust cam positioning sensor about a year past, 20k miles. In addition to the trouble code generated, another symptom of the failure was a tailpipe exhaust note coming from the engine bay. Great exhaust suround sound! The M5 board indicated that this can be a sympton of the CPS failure. I'm a bit confounded as to how that exhaust sound was generated?

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    Quote Originally Posted by thegunguy View Post
    The one thing I can add is that I love my stubby 3/8" articulating ratchet. If you plan on doing this repair, you might want to grab one. It really helps you get maximum rotation in the cramped space.
    Got any pics of this ratchet or part numbers. I just replaced the passenger exhaust CPS on my M5 at 60K miles. So I have 7 more sensors between the 2 cars that will eventually need my attention. That sounds just like the tool I will need. You are correct in that the one I have done is by far the easiest, so I will need all the "help" I can get on the others.

    thanks
    Mark

  9. #9
    It certainly seems like doing the MAF's and these sensors all in one go could ensure better running, but the M5 guys don't seem to think it is worth doing everything at once.
    Andrew Macpherson

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  10. #10
    Administrator thegunguy's Avatar
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    Quote Originally Posted by SProZ8 View Post
    I replaced a left exhaust cam positioning sensor about a year past, 20k miles. In addition to the trouble code generated, another symptom of the failure was a tailpipe exhaust note coming from the engine bay. Great exhaust suround sound! The M5 board indicated that this can be a sympton of the CPS failure. I'm a bit confounded as to how that exhaust sound was generated?
    You got me on that one because it's only the exhaust cam sensor, not on the actual exhaust path. I wouldn't count this as an actual symptom, unless the default setting the the PCM goes to with the code adjust the cam timing in such a way that the sound is changed.

    Mark, here's the one I have. The flexy handle is the best part.
    http://www.sears.com/shc/s/p_10153_12605_00944834000P?vName=Tool%20Catalog&cName=Mechanic'sTools&sName=Drive%20Tools%20&%20Ratchets&psid=FROOGLE01&sid=IDx20070921x00003a

    I also have a thin profile ratchet as pictured in one of the M5 threads that is handy as well, but I didn't find it necessary - for this sensor.

    Andrew, it could make sense to change all at once as you already have some common pieces off.
    thegunguy

  11. #11
    Z8 Ate My Homework! Norcal's Avatar
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    Is there a check for all this? My car is going to Dana in a couple weeks, and I've never done the MAFs or any sensors.

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    A faulty CPS will cause a Check engine light (CEL). One would then use a code reader to determine the cause of the light. There is probably no reason to change out a CPS until a fault code appears identifying a defective CPS. So, if your visit with Dana reveals no CPS code, no reason to change them.

    There are those on the M5 board who feel the MAF can deteriorate both on time and miles. Additionally, their function can degrade gradually effecting performance, but not be so out of spec to activate a CEL. A truly defective MAF will cause a CEL, however. On the M5, there is a way to pull up on the computer a rate of fuel consumption in liters/hour. A number in the range of 140 l/hr at full throttle near redline is said to indicate a healthy MAF. I do not know if this data is available on the Z8. I replaced the MAF's on my Z8 at 50K miles and subjectively it ran stronger. (Possible placebo effect) It was not giving any CEL at the time. There are many on the M5 board who have done the same thing at a similar mileage and had a subjective benefit.

    MAF's can be purchased at Bimmerzone.com for 365.00/pair and are easy to install. A dealer would be much more expensive. Based on the age of your Z8 alone, you may "feel" a benefit. Just need to decide if the expense is worth it. Certainly not required if there is no CEL pointing to MAF problems.

  13. #13
    Z8 Ate My Homework! Norcal's Avatar
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    Thanks for the info. I've read about this all along the way. Now at 30k+ but no CEL, so I'm not going to change anything.. she's running strong and fine for now.

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    Administrator thegunguy's Avatar
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    Ian, lets grab lunch next week. I'll bring my code reader.
    thegunguy

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    Z8 Ate My Homework! Norcal's Avatar
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    I'll call you Saturday. Robbie is in town. We should go visit him in WC around 2.

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    [QUOTE=thegunguy;21188]Finally tackled this one today. It's a fairly easy operation other than the tight access to the sensors at the back of the engine. I only replaced the faulty sensor, but I did get familiar with the other three for the inevitable future replacement, and the passenger exhaust sensor (the one I replaced) is most certainly the easiest.

    Did you try this from the bottom of the car as others suggested or was it easier to do it from the top of the engine?

  17. #17
    Rifle, when you see Ian make him call me and give me dates, he is harder than an actor to get a commitment out of!!
    Andrew Macpherson

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  18. #18
    Administrator thegunguy's Avatar
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    On the Z8, from the top is really the only way to go. The option from below applies to the roomier engine bay of the M5. If you're replacing them, you might consider doing all four (2 intake, 2 exhaust). They're in roughly the same location on each bank (intake on top, exhaust on bottom - or inside and outside depending on your perspective). There is a unique part for intake and exhaust. It's a fairly simple procedure. See my notes below, especially on some helpful tools.

    Will do, Andrew. I know is mad busy right now as business is really booming for him lately. Kudos to someone in this economy.
    thegunguy

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    Thanks for the tip. That helps quite a bit.

    I'm still confused by the locations of the sensors. I thought the intake ones are at the front of the engine (near the radiator) and the exhaust ones are at the back of the engine (close to the windshield). According to your description, are they roughly in the same spot (close to the windshield) with the intake sensor on the top and the exhaust sensor below it? Did you have to remove any air ducts or hoses?

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    It has been a while since I replaced one, but there are two on each side at the rear of the cylinder head. Access to them required removal of the shrouding that surrounding the heater box, right side and the brake/clutch master, left side to get enough working room. I don't recall whether the upper CPS is the exhaust or the intake. You might check the diagrams on realoem.com. After purchasing the replacement CPS, about $100, the tools and installation were self evident.

  21. #21
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    Sorry, I forgot to respond too. Yes, both the intake and exhaust CPS are on the firewall side. The intake is on the inside of the V, which makes it "on top". The exhaust is outboard - "on bottom". Accessing each can be tricky. The passenger bank didn't require removing anything. The driver's side is more difficult, but I don't recall what all I did to gain access.
    thegunguy

  22. #22
    top down in seattle bvhbmw's Avatar
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    MAFs are easy to pull, clean and reinstall. Use MAF cleaning spray and let them dry completely before reinstalling. Check the m5board for instructions.
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  23. #23
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    I was able to pull the driver side exhaust CPS. I had to disconnect the heater hoses to do this. Took a while but it was relatively easy. The driver side intake CPS is another story. Very hard to turn. I think I might have stripped the Allen bolt in the process. Now I'm stuck. I'll need to figure out a way to cut the bolt. What a pain.

  24. #24
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    Not your fault, but anti-seize is a must on re-install.
    thegunguy

  25. #25
    Administrator thegunguy's Avatar
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    19K - on the way back from Point Reyes for the weekend, a block from home, and I saw the lovely SES light. This time it's the driver/exhaust sensor. Last year it was the passenger/exhaust.

    I just ordered three sensors (one replaced last year) - ~$350. Now I need to get a box of bandages for my knuckles when tackling the driver side sensors.

    Fun project soon...
    thegunguy

  26. #26
    Administrator thegunguy's Avatar
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    I replaced the faulty sensor yesterday afternoon, along with the two others that are likely near failure. As noted in the threads from the M5 board in some of my original posts on this topic, the current sensor offered by BMW is different than the original ones. I'm hoping the new design has a longer life. Around 20k seems to be the usual failure range on the original sensors.

    The driver's bank sensors are really easy to do with removing the fence between the engine and the brake booster. Popping the vacuum line running to the booster gives you a little more room to work. Easily an hour or under for the two.

    The passenger bank sensors are harder due to the harness that runs from the back of the engine. I did the exhaust sensor last year without too much trouble from the top, but this time I put the car on stands and went after the intake sensor from the bottom. From that view, I'd definitely approach the exhaust sensor that way in the future. If you have a lift, from below is probably the easiest method on either side.

    Anyway, it's an easy afternoon repair, and I enjoy getting under the car to check things over even though the Peter Pan team do a great job keeping everything in check on my semi-annual checkups. It's a great way to bond with the car.

    Afterward, we went for a test drive!
    thegunguy

  27. #27
    Z8 Millennial Monster hayvenhurstkid's Avatar
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    I think you could have gotten a better deal on the price of the sensors.
    Marty

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  28. #28
    Carter Carter Rise's Avatar
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    I am about to tackle the intake sensor 2. Its listed as cyl 5-8. Do any of you know if that is drivers or passenger side?

  29. #29
    Administrator thegunguy's Avatar
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    I'm not aware that the sensors have numbers, but cylinder bank 1 is the passenger side (1st cylinder is at the front). Bank 2 is the driver side (5th cylinder at the front). So, I'm going to guess that the intake sensor 2 is the intake sensor on the driver side. It's a pretty easy one to reach on the top, inside of the bank.

    I always encourage changing all the sensors as they tend to fail around the same time, and you can save some labor at the shop or prep and familiarity time if you go DIY.

    Did you get a new o-ring with the sensor?
    thegunguy

  30. #30
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    Thanks. I decided to do them 1 at a time, primarily because I thought I would try to do it myself. If I hate it, I'll get the dealer to do the others.

    I'm still cogitating on approaching from the top vs the bottom....

  31. #31
    Administrator thegunguy's Avatar
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    On the driver's side (bank 2), I think it's easiest to get at it from above. All you really need to do is remove the fence between the engine and the brake system. Two bolts I think (one by strut tower and one by firewall), and pull up. It will give you a little more room. You can also move the coolant return hoses around a little.

    From below gives you a clear shot at both sensors, but the manifold is in the way, making it a tight fit. I have pretty long arms (longer I should for my 6' 2" frame), and the intake sensor is just at the end of my reach using floor stands. If you have a lift, it might be the way to go, but you'll still have to squeeze past the manifold.

    Make sure you get a new O-ring. I've seen them come with the sensor and not.

    It's a very doable repair for anyone with a basic mechanical interest and the ability to contort.

    Be sure to review my tool suggestions, and good luck.
    thegunguy

  32. #32
    Carter Carter Rise's Avatar
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    Thanks. I did buy the o ring and followed your suggestion on the tools. My contortions are usually verbal, though, so i think I'll try it from the top.

  33. #33
    Administrator thegunguy's Avatar
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    Sounds good. PM me if you need help.
    thegunguy

  34. #34
    Z8 Ate My Homework! Norcal's Avatar
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    From the top? From the bottom? Have you tried it from behind? ; )

  35. #35
    Administrator thegunguy's Avatar
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    I'm not falling for that one.
    thegunguy

  36. #36
    Carter Carter Rise's Avatar
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    I will still have 2 sensors that will certainly go bad as soon as I finish this one, so I expect I will try the other positions for them.

    I haven't seen a hose clamp like this one on the brake booster before. How do I remove it wihtout destroying it? (hopefully the picture I attempted to attach will show up).
     

  37. #37
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    It's just a vacuum hose. Pull out on the plastic fitting HARD. Don't remove the clamp. It's a single use.
    thegunguy

  38. #38
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    This thread brings back good memories of when I was much younger and did most of my own repair work on my car. The car was a 75 (not very sure of age, but certainly the first generation) VW Scirocco

    Now days, I open the hood and stare at it for a minute before quickly realizing there's not much that I rather do myself.
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  39. #39
    Administrator thegunguy's Avatar
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    The Z8 is a surprisingly approachable car for personal maintenance, especially in the days of code readers on your phone.

    I generally take my car to Dana and Matt for most things, but I really enjoy doing some repairs and maintenance myself. It's a great bonding experience with the car, and you do learn a lot about it over time, especially when viewed from below. There are fun details to explore underneath, and you can observe the care the guys took when when hand assembling the body. It's kind of neat to see a weld and think, there's a guy on the other side of the globe that did that. It's beautiful.

    Also, my grandfather was an part-time auto mechanic who also did body repair (his main career was maintaining a VOR radio for air traffic navigation), but that was a time when it meant such people could pretty much repair, fabricate, or build anything as the mechanics and electronics were so much simpler. He use to have a pretty good side business buying wrecked cars, restoring, and selling them. I have fond memories of my youth working with my grandfather on cars, building stuff, welding, plowing on his tractor, etc. So, I try to keep that alive. I like to keep my hands trained and let my mind wonder into all sorts of fields. He was an inspiring guy.
    thegunguy

  40. #40
    Nice story, thanks for sharing!
    Andrew Macpherson

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  41. #41
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    Great story.