ETM and Mass Airflow Sensor Failure Symptoms and How to Replace MAF - Page 2
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    1. #36
      Member burnout8488's Avatar
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      Any MAF sensor specified for a 99 or 2000 S70/V70/C70/XC70 will work on your car. 98 will not, different connector.

      No idea where you could get Volvo parts in Israel, but FCP ships worldwide. http://www.fcpeuro.com
      '13 BMW X1 35i M-Sport
      '99 S70 AWD - 15G - ARD Green

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    3. #37
      Quote Originally Posted by burnout8488 View Post
      Any MAF sensor specified for a 99 or 2000 S70/V70/C70/XC70 will work on your car. 98 will not, different connector.

      No idea where you could get Volvo parts in Israel, but FCP ships worldwide. http://www.fcpeuro.com
      really? there is no difference between the denso and me7 engines?

    4. #38
      George has given us a great post. I have read it a few times in the last weeks because my car is experiencing symptom #5 predominately. So I replaced the MAF before the ETM - with terrific results.
      Also, MAF failure often presents itself as a staccato of multiple hesitations or attempts to stall, a fraction of a second apart, while ETM failure is often one such hesitation per episode.
      Plus it was generally sluggish, worse early mornings.

      I'd had erratic idle too and surging when coming to a stop but a throttle body clean cured that.

      I took the car to our local Volvo dealer. Their scan revealed ETM and coil problems. Their advice was replace the ETM then see if the coil problems persisted and possibly replace them. No promises this treatment would restore my car to normal performance. So I decided cure it myself. I bought a VIDA and scanned myself. Sure enough the scan revealed.

      ECM 3503, ECM 3513,3523,3533,3543,3553
      ECM 917F, ECM 91A7 ECM 91F0 (ETM codes)

      But since I'd read George's post I replaced the MAF first. Immediately the car was better to drive, but not perfect. Still some misfiring at highway acceleration. However after 150km driving I couldn't detect any problems. So I connected the VIDA again and found zero fault codes. The car drives perfectly, no fault codes, replacement MAF fixed the problem. ZERO faults!

      My theory is the faulty MAF was causing the ETM to try to correct fuel/air mixture based on spurious MAF values. It couldn't and while fluttering it caused misfiring and bad ETM codes. With stable MAF readings it has settled down and performs as designed.

      Thanks George for helping me identify the real culprit. I'm disappointed the system doesn't work out it has a MAF problem, but throws ETM faults. I'm sure many people have just assumed ETM problems because the fault codes indicate it.

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    6. #39
      Junior Member UKJamesV70's Avatar
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      Fantastically detailed account, enough for anyone to be able to undertake this operation. I have saved this as a separate document on my desktop for quick and easy reference; thank you for taking so much trouble over it.

    7. #40
      Thanks George terrific info.
      I had an experience with the Throttle Body unit that was causing an emission issue. I couldn't pass the emission test and didn't know why. I took it to the Volvo dealer and spent $300 to have them fix the issue.
      They gave me a tune up ( lame ). I took the car to a local mech. and he cleaned the Throttle Body and all was good, and I just passed inspection again. One thing I learned from all this is how to clean the Throttle Body Unit myself.
      After screwing up my courage I took out the four bolts dropped in the unit carefully on a rag without disconnecting any wiring, spraying throttle body cleaner on the butterfly unit and cleaning with an old cotton tea shirt. The gasket didn't
      need to be replaced and after spraying a couple of times with the cleaner and doing a final clean with some Q-tips, I was happy with myself. Easy to put back together.
      If I can do this anybody can do it. I clean it every 4 month's just in case and haven't had any issues since.

    8. #41
      Quote Originally Posted by 1999s70 View Post
      As one who is on his 5th Electronic Throttle Module (ETM) and 4th Mass Air Flow Sensor (MAF), I’d like to write of my experience with these, in particular noting the symptoms of their impending failure (so that you don’t suddenly find yourself with a stalling car as an 18-wheeler barrels down on you from behind), and also telling you how to replace the MAF yourself and save lots of $$.

      The ETM issue is well-known among those lucky Volvo owners who have the 5-cylinder engine in models produced in 1999, 2000 and 2001. Like me . Volvo has extended the warranty on original throttle bodies, for up to 10 years or 200,000 miles, and that discussion has, I’m sure, been had many, many times and is beyond this post. In my experience, throttle bodies last around 70,000 to 90,000 miles, though I did get 118,000 out of my original one.

      Background:

      The air intake path, at least on a naturally aspirated (NA) engine, is as follows:

      Air Filter --> Mass Airflow Sensor (also called the Air Mass Meter, or MAF) --> Throttle Body --> Intake Manifold

      The throttle body contains a metal “throttle plate” that pivots along its diameter, allowing more or less air through. The car’s computer determines the plate’s position based upon, among other factors, engine speed and load, engine temperature, and accelerator pedal position. Within the throttle body is a “throttle position sensor” which, I understand, is nothing more than a strip of resistance film, over which the throttle place moves. Depending upon the location of the throttle plate’s edge, the electrical resistance through the sensor strip tells the computer the exact throttle plate position. Minor adjustments to this position are made by the MAF, which senses temperature and humidity. For example, hotter, more humid air has fewer oxygen molecules available for combustion (hot air less dense, oxygen displaced by water vapor), so the throttle plate opens slightly more than “normal” in this situation. If it did not, then you’d have less oxygen in the cylinders, which would either cause the engine to run “rich,” wasting fuel and possibly fouling spark plugs or catalytic converters, or the car’s computer would reduce the fuel charge into the cylinder, with a corresponding loss of power. More precisely, your car would perform noticeably different depending on temperature, humidity, altitude, etc.

      Eventually, after the throttle plate rubs over the throttle position sensor millions of times, the resistance film begins to deteriorate. As time goes on, the computer will be unable to determine the throttle plate’s position. My thought is that the MAF tries to compensate for some of the early throttle position sensor failure, and, in turn, it’s quite common for the MAF to fail shortly after the throttle. By “shortly after,” I’m talking, perhaps, 5,000 miles – much too long for most people to connect the failure of these two components – but, since I often drive that much in less than a month, and have had these components fail several times, the connection has been more than obvious to me. As for the throttle position sensor itself – my experience has been that the throttle body will last longer if you drive a variety of speeds, and it lasts the shortest time if you, for example, do the vast majority of your driving at, say, highway speed (minor fluctuations, rubbing the throttle position sensor, all happen at the same place on the resistance film).

      Symptoms of ETM and MAF failure:

      By the time the ETS light comes on your dashboard, and the car goes into “limp home mode,” the throttle has totally failed, though turning off the engine and restarting it will often clear the ETS light and enable you to drive normally for a short time.

      But, here are the earliest symptoms of ETM failure, most of which would probably go unnoticed:

      1. The earliest symptom happens in this circumstance – after driving steadily for a while at highway speeds, you come off the highway and have a series of stops – at traffic lights, or whatever – each time, the engine speed will drop noticeably below the 900 rpm idle speed, then come back up to 900, with an ever-so-slight surge. The feel is almost as if your transmission is downshifting from second to first gear too late. A normal throttle will not do this – if you watch your tachometer as you slow down, your engine speed will almost never go significantly below idle speed. Also note that the original idle speed for these engines was 850 rpm – this was increased by 50 rpm during one of the earlier “throttle software upgrades” – which has the effect of masking this particular symptom, at least for a while. My experience is that, once a throttle starts doing this consistently, though it can be intermittent, the throttle has around 25,000 miles left on it.

      Later in this stage of deterioration, you’ll also notice that your engine speed drops too low when coasting at moderate or highway speed. For example, normally my tach will read around 1500 rpm when I’m coasting at 40 mph. When the throttle starts acting up, my tach will read as low as 1000 or 1100 rpm while coasting at 40 mph, though the engine is in no danger of stalling. This symptom is also intermittent.

      2. The next symptom is “hunting at idle.” This means that, when you experience symptom #1 above, but are now stopped at, say, a traffic light, you’ll sometimes see the idle speed fluctuate slightly. Again, a normal throttle, with a warm engine, will not do this. Here, the feel is like, say, the a/c compressor is cutting in and out, which often momentarily raises or lowers the engine’s speed. But – the throttle symptom will happen even when the a/c is shut off. You will not be able to create the hunting situation at this phase of failure, though you will be able to induce it later.

      3. Eventually, you’ll feel momentary hesitation when driving at highway speeds, almost as if there’s a gust of wind pushing the car back. When this happens, I look at shrubbery to see whether there is a significant wind – and, if there isn’t, then it’s likely to be the throttle, especially if it has lots of miles on it. At this stage, the car is in no danger of stalling, but it’s one of the last signs that you’re getting close to a true failure – figure 5 to 10 thousand miles remaining on the throttle.

      4. When the throttle actually starts “failing,” you’ll feel a significant jerking motion as the engine tries to stall, often at highway speeds. Stepping on the accelerator pedal will, momentarily, do nothing. This can be quite unnerving to the uninitiated driver, or for passengers. However – you CAN get out of a potentially bad situation, merely by manually shifting the transmission down one gear – this increases the engine speed, which means that the throttle plate will now open to a place where the throttle position sensor is not as badly worn, and the hesitation episode will be over. You can upshift and chances are that the throttle will not fail again at that point – though you’re now on borrowed time, and a complete failure can happen at any time. Once the throttle has reached this point, hunting at idle will be very common, even with the engine cold, and the car may also be hard to start. It’s quite likely the there would be no codes stored in the car’s computer, although a failure to start may leave something behind.

      You will also be able to induce hunting at idle, especially if the car is warm – with the car stopped, one foot on the brake, and the transmission in drive (I’ve also had this work with the transmission in park, but I’ve found it’s more likely to happen with the transmission engaged), use your other foot to step on the accelerator to raise the engine speed to, say, 2000 rpm. A normal throttle will return the engine speed to 900 rpm in one smooth movement, with little or no overshoot. A failing throttle will often allow the engine speed to significant undershoot 900 rpm, then have the speed go well over 1000, drop well under 900, and continue to fluctuate with no further driver intervention – until the car stalls, or it settles in, sometimes with another tap on the accelerator. I have also had this happen spontaneously – once my car did a command performance on a test drive with a Volvo shop foreman as my passenger – needless to say, that scenario produced an automatic throttle replacement, no questions asked J .

      5. Failure of the MAF appears much like those of paragraphs 3 and 4, minus the hunting at idle – except that downshifting does absolutely nothing because the problem is not that you need to run the engine at a different speed to use a different portion of the throttle plate’s path, but that the throttle is getting faulty information from the MAF sensor. Also, MAF failure often presents itself as a staccato of multiple hesitations or attempts to stall, a fraction of a second apart, while ETM failure is often one such hesitation per episode. And MAF failure is more likely to show itself on extreme weather days, since the sensor would normally be providing the most correction to the ETM. Again, early failure often does not leave any codes in the car’s computer.


      What to do when the throttle starts failing?

      Once your ETM has started to fail significantly, meaning that you’re seeing symptoms from my paragraph 4, you have several options.

      First is that you can do nothing, living with the problem until the ETS light comes on. Murphy’s Law being what it is – this will happen when you’ve taken the car camping in a remote location, or when you’re sandwiched between two 18-wheelers at 70 mph, or you pull out to pass on a two-lane road, get to the oncoming traffic side and the car stalls when you step on the accelerator. Besides, stalling and hesitation ought not to be a way of life.

      Second is that you can take your car into a Volvo dealer. Note that the ETM must be replaced by a dealer – the actual mechanics of the replacement involve four bolts, a hose clamp and wiring connections, and probably take no more than 10 or 15 minutes – but software has to be loaded so that the new ETM is known to the ECU, and is properly “integrated” into the car’s electronics. If there are no error codes and no ETS light, often a dealer will either do nothing, or they’ll offer you a throttle body cleaning. I’ve heard both good and bad things about this service, though I’ve never had it done, myself. It’s also a DIY project, for those who care to try it. My opinion is – the cleaning, if done at a dealer, costs about $250 – a new throttle costs around $1000 – if the current throttle has at least ¼ of its life left in it, or you’re about to sell or trade the car, then it pays to do the cleaning. But – since throttle failure symptoms made you come into the dealer in the first place, while it’s quite possible that the cleaning may help for a short time, you’ll soon be back again, $250 poorer, facing a throttle replacement, anyway. But – Volvo will often resist replacing the throttle at this point, especially if it’s under warranty. The dealer will test drive the car, but without codes and/or an ETS light – if the car doesn’t do a “command performance” when being test driven, you will have to argue your point. If you have worked with a dealership that knows you and trusts your feedback on the car’s drivability, you may get your way.

      Sidebar – why should the throttle body need cleaning, in the first place? After all, it’s on the output side of the air filter – the throttle body should only be seeing filtered air. It turns out, however, that Volvo vents the crankcase fumes into the throttle body, so that they can go into the cylinders and be burned. Great for the environment; bad for the throttle. After a while, the throttle will have an accumulation of gunk that probably should be cleaned – but this will, more than likely, have no impact on the deterioration of the throttle position sensor resistance strip. And – I’ve also heard of dealers who offer throttle cleaning as a way to postpone throttle replacement until after a warranty expires, so that they don’t have to replace the throttle for free.


      Replacing the MAF sensor

      As I’ve mentioned, my experience (and that of several dealers to whom I’ve mentioned this) is that the MAF sensor often fails shortly after the ETM. Fortunately, this is a very simple DIY fix that requires a new MAF sensor (available at a nice discount from FCP Groton, for example), a 10 mm socket, a screwdriver and about 5 minutes of your time.

      1. Locate the MAF – it’s inserted into to the output side of the air filter housing. It’s held in by two 10 mm hex head screws, and has a large diameter air hose clamped on to its output – this hose goes to the throttle body. The MAF sensor also has a wiring connection on it.

      2. Disconnect the wiring connector – there’s only one way that it can be reattached, so don’t worry about keeping its orientation.

      3. Locate the hose clamp’s screw and loosen it a few turns – enough to slide off the hose.

      4. Loosen the two 10 mm screws holding the MAF and remove them – don’t drop them into the engine, making a 5 minute repair take an hour while you look for them .

      5. Pull the MAF sensor out of the air cleaner housing – it’s simply pushed into it and held in place by its rubber gasket. Gently twisting the MAF, or rotating it, may help. If you want, you can take off the air cleaner housing top and pull out the MAF with the air cleaner housing off the car.

      Installation of your new MAF sensor is the reverse of removal.

      I keep a spare MAF sensor in my garage – now, when an ETM gets replaced, I go home and replace the MAF sensor that day, then order another one when I can get a good deal on price, free shipping, etc. on a replacement spare.

      I do hope that this post helps identify failing throttles and MAF sensors, and saves someone from driving a car with a potentially dangerous situation. It can also give you advance warning of an upcoming maintenance expense if your throttle needs to be replaced outside of warranty.

      Please feel free to add your experiences to this thread, especially any other early failure symptoms. I'm hardly a "Volvo Expert" - just someone who's been through the ETM and MAF replacement process a few times.


      Much thanks for this post. 1999S70

      I have cleaned the MAF, but the problem is coming back more frequently; so I guess it's the ETM.
      I have the appropriate cleaner. Members should be aware that the MAF should have a very special cleaner;
      and there is another one for the ETM. (Throttle body).
      Regards to all.

    9. #42
      I don't own a Volvo, but I found this information regarding symptoms of a MAF sensor failure very helpful. And I would like to highlight it to anyone with a similar problem with their mass airflow sensor. I will confirm after replacing my MAF sensor, but after a lot of research this is the most accurate symptoms of my problem. Also, my MAF only acts up on first start-up in extreme cold weather days after sitting overnight; idle surge, multiple hesitations and attempts to stall fractions of a second apart. When unplugged under these conditions, the idle goes back to normal and the truck runs good. This problem also triggered a P0300 random misfire code. Hopefully this information will be helpful to others, as it was to me. I have already cleaned the MAF sensor with the appropriate cleaner as well.

      "5. Failure of the MAF appears much like those of paragraphs 3 and 4, minus the hunting at idle – except that downshifting does absolutely nothing because the problem is not that you need to run the engine at a different speed to use a different portion of the throttle plate’s path, but that the throttle is getting faulty information from the MAF sensor. Also, MAF failure often presents itself as a staccato of multiple hesitations or attempts to stall, a fraction of a second apart, while ETM failure is often one such hesitation per episode. And MAF failure is more likely to show itself on extreme weather days, since the sensor would normally be providing the most correction to the ETM. Again, early failure often does not leave any codes in the car’s computer."
      Last edited by Silverado1500; 12-04-2014 at 09:04 AM.

    10. #43

      Another great option is to have your ETM rebuilt using new technology.

      I found this company, XeMODeX, on the Internet that will take your failed ETM and rebuild it using a new technology that eliminates the sensor strip in the ETM that is the cause of all the problems. I shipped my faulty ETM to them on a Friday and it was rebuilt and returned the next Monday. The new technology they invented uses magnets so there is not physical contact in the sensor and thus no wear. They give a lifetime warranty and you don't have to have the software replaced because you get your actual ETM back. I have a 1999 V70 non-turbo 2.4. I have had no problems since installed the rebuilt ETM. The shipping is a little steep and you have to follow the shipping instructions exactly because the company is in Canada. If you set up everything on line they give you a discount. I gave them a call before I sent my ETM off just to make sure everything was on the up and up. It cost about half what a new ETM (with the old technology) would cost including shipping. You can check out the ETM section of their website at http://xemodex.com/us/product/electronic-throttle-module-etm-for-volvo/ This is my first post here. I sure hope it helps out a lot of people.

    11. #44
      Hello, I have an odd ETM/MAF problem on my 2001 V70 Turbo. It goes into limp mode if I accelerate hard it goes into limp mode, and I get the ENGINE SRVICE REQUIRED URGENT message. Stopping and restarting the engine clears the fault.
      The ETM was replace under warranty years ago and the MAF has been replaced with the genuine Bosch part.
      I am running the car with the MAF unplugged and it runs perfectly after the first few lumpy seconds. Only problem is cruise control will not work with the MAF unplugged.
      I have tried another MAF from a friends car, and my MAF on his.
      I think it may be a connector – I had exactly the same problem after disturbing the wiring when changing the headlamp bulb on the MAF side, after much fiddling about the fault cleared for over a year.
      Any suggestions anyone?

    12. #45
      Member ScottishBrick's Avatar
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      Quote Originally Posted by mpe View Post
      Hello, I have an odd ETM/MAF problem on my 2001 V70 Turbo. It goes into limp mode if I accelerate hard it goes into limp mode, and I get the ENGINE SRVICE REQUIRED URGENT message. Stopping and restarting the engine clears the fault.
      The ETM was replace under warranty years ago and the MAF has been replaced with the genuine Bosch part.
      I am running the car with the MAF unplugged and it runs perfectly after the first few lumpy seconds. Only problem is cruise control will not work with the MAF unplugged.
      I have tried another MAF from a friends car, and my MAF on his.
      I think it may be a connector – I had exactly the same problem after disturbing the wiring when changing the headlamp bulb on the MAF side, after much fiddling about the fault cleared for over a year.
      Any suggestions anyone?
      VIDA scan it to identify the problem instead of guessing. Your issue may be something entirely different
      1999 V70 T5 - Emerald/Graphite M56H - 119k - The Garage Queen
      1999 V70 T5 - Pewter/Graphite AW42 - 241k - The Daily
      1995 945 Turbo - 425k, 1994 945 Turbo - 234k, 1993 945 Turbo - 318k

    13. #46
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      VIDA scan exactly....I thought for sure i had another damn ETM issue....scan showed a bad BPS..easy fix... Thanks VIDA !!!
      99 V70T5 Full 3" exhaust CJ DP Snabb Intake Yother Strut Bar H&R springs Koni Adjustables rear IPD sway 15mm rear spacers IPD HD swaybar endlinks R steering wheel

    14. #47
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      Car is a 2006 V50, currently about 85,000 miles. I am having VERY few of the "failing throttle body/MAF" symptoms, and what is occurring is of minimal enough effect that for the last 20,000 miles, I haven't bothered to do anything about it other than adding a pint of Techron fuel-system cleaner to the gas, which seems to fix everything for several thousand miles. But can anybody tell me what component is failing, based on the following?

      1/I get a sudden "Decreased Engine Performance" light. The effect, however, is unnoticeable at cruise or ordinary around-town driving. Only if I try to accelerate hard does the car bog down. There has NEVER been an accompanying check-engine light. Nor has there been the slightest feeling that I am in any kind of limp-home mode

      2/The DEP light usually goes away at the next startup, and adding the Techron seems to temporarily cure the situation anyway.

      3/There has never been any change in idle or any other tangible sign of decreased engine performance other than the car resisting hard acceleration. Under normal (for me) gentle acceleration, the car seems just fine.

      What should I be replacing to cure this once and for all? Or should I simply do a throttle-body cleaning?

    15. #48
      Junior Member kampman's Avatar
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      You'll get better answers in the S40/V50 forum but that doesn't sound like a throttle problem - I'd be checking ignition components first. How old/worn are the spark plugs?

      The P1 cars like yours and mine use an entirely different throttle module than the one being discussed in this thread, so while some of the advice is relevant I wouldn't take much of it as gospel.
      1966 220: eventual Ecotec swap project
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      2006 V50 T5 AWD M66: 121K

    16. #49
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      Yeah, I posted here by mistake and have since posted it on the V50 subforum. Thanks! (Sparkplugs are less than 20,000 miles old, by the way and they are high-quality plugs--platinum Densos, as I remember.)

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