Lost power 2l Z3 2000 MY

[therealdb1]

Hi,

This is a bit of an ongoing problem that I keep thinking that I've fixed only to discover that I haven't and now the MOT is due!
The car is is a 2 litre Z3 registered in October 2000. 52TU engine.
When I first tried to fire it up for this summer it refused to run. Shortening a long story, an inlet cam sensor and new MAF cured the problem. Since before the last MOT the ABS warning light would intermittently illuminate and I just put this down to a wheel sensor that I would get around to one day.
On the last couple of trips out, things would start off ok but then the EML would illuminate and the engine obviously went into limp home mode. Checking the DME codes I get 119 (0077 hex) repeatedly coming up even after a reset. I'm pretty sure the MDK is not stuck since for a while the car runs fine.
Another shortening of the story is that today I replaced the MAF with another unit (genuine Siemens as per OEM) but code 119 recurs. What I have noticed is that the ABS light is permanently on now so I am beginning to suspect that the ASC is malfunctioning causing the MDK code to be produced. A possibility?
Checking the ABS codes I get 49 (0031 hex), 50 (0032 hex), and 148 (0094 hex). My trusty Bentley manual gives 50 as a solenoid vale but doesn't advise which one and 49 and 148 are non-existant in the table applicable to my car.
I now suspect that more than one wheel sensor has failed or the ASC control unit has given up.
Anyone know what the above combination of codes is telling me?
Is my line of thinking credible?
Regards Chris

[Del]

Excuse my ignorance but what type of code reader are you using and what is MDK?

[therealdb1]

Hi Del,

I'm using P A Soft BMW Scanner software running on an XP laptop with an interface unit that goes from the laptop COM1 port to the 16 pin Pacman socket under the bonnet of the Z3.
It reads each control unit in turn, reporting how many errors are stored for each in a complete scan, or you can direct it to specific targets which is what I did this morning; DME which is the computer that takes care of engine management and then the ABS computer which is responsible for the anti-lock brakes and traction control.

The MDK is the motorised throttle body. Although these cars look like they have a throttle cable, for normal running the throttle is operated by an electric motor controlled by a combination of the DME and ABS computers.

I am confident that the throttle is not stuck because with the car stationary the engine will rev in response to pedal movement but then as the revs increase a mis-fire is introduced which I believe is the traction control coming into operation. The traction control that I have apparently not only interrupts the throttle position indicated by the pedal position but also fiddles with the injectors and applies brakes too. This is why I am asking about the ABS codes that I have no definition for.

It's a shame that BMW feel the need to put these things on board to cause me grief when faulty as the 2 litre engine isn't that torque laden to require traction control. My 330 hp rear drive Jaguar managed without these bells and whistles although that had plenty of electronic problems of its own not relevant to this forum.

Chris

[Del]

Sorry for the daft question I’m only familiar with my cheap & cheerful OBD II system and to some extent the INPA system.

If you have the more sophisticated ASC/DSC which can override the engine management system, my understanding is that the warning lights “blink” when in intervention mode and when permanently lit are in “switched-off” mode. As you are having (or have had) misfire issues do you think the problem might instead be with a throttle position sensor (TPS)? Would a faulty wheel sensor erroneously intervene to actually cause an engine misfire? – I believed a failed wheel sensor effectively switched off the ASC/DSC?

My understanding is that you have two TPS one of which is an integrated part of the ASC/DSC system. I wonder whether something like INPA might help pinpoint a possible problem with this sensor.

http://www.zroadster.net/forum/viewtopi ... 18&t=35789

[therealdb1]

That's a good point, Del.
When a wheel sensor goes down the ASC / ABS is disabled. My thinking was that if both front wheel sensors fail then any movement from the rear wheels may be seen as wheelspin and ASC the activates. My thoughts overnight were that this cannot be the case since the ABS light is on from the turn of the key and as I previously said the EML will light up when the misfire starts even when the car is stationary.
I guess I was just clutching at straws rather than facing up to a replacement MDK which is awkward to get at and also expensive. I don't think that the TPS is a replaceable item on those throttle bodies. Anyone else know?
I shall have to get the codes read by a more elaborate system to narrow down the problem before throwing time and money at it in the hope of curing the fault.

[therealdb1]

Hi, I got the codes read by a more elaborate machine but all that was coming back was sluggish / stuck throttle. The chap who read this from my car was reluctant to go further as he doesn't believe that the throttle is stuck either from the results of his tests but suspect the TPS which is where Del and I were heading. The problem is that the TPS is not replaceable on these cars and it means a new throttle body at £450 from a dealer and there is still the possibility that the fault will not be cured. There appear to be plenty of used ones around at about £60 with the correct part number but there appears to be a blue label and yellow label variety.
Anyone know the difference?
I'm not sure I can tell what I have until I remove it rendering the car immobile whilst I wait for a replacement to arrive and me to get around to fitting it.
Is it worth getting a second hand unit or does anyone know where I can get a reconditioned throttle body with a guarantee?

[Robert T]

The throttle on the 2.0 looks to be cable operated but with an override for the ASC/DSC to be able to back off the power to maintain control of the car, similar to that on my M44 1.9.

Does the ASC/DSC light also illuminate when the ABS light it on? The two systems are very closely linked, and often one light accompanies the other. If the control unit has failed, then both systems will not be functional, and I'd expect to see both lights on.

I'm afraid the codes you have read mean little to me - I use INPA which gives descriptive messages - though my version currently gives them in German!

Whilst it is possible that a defective wheel sensor could cause ASC/DSC to activate, I would expect it to also have logged some out of range values as well, and this have some error codes recorded. The telltale flashes when ASC/DSC activates - do you see this? Does the light illuminate at startup? What happens when you press the button to turn ASC/DSC off? Just thinking that your bulb might have blown, as if it is okay and not flashing, then I think we can rule out ASC/DSC activating of its own free will.

For reference, what is the build date of your car? Model Years are rather inexact and registrations dates mean nothing. The build date is given on a sticker on one of the front suspension strut towers, the other giving the paint colour.

Cheers R.

[therealdb1]

Hi Robert,

Thanks for the reply.

The build date is April 2000.

From what I gather the throttle on these is odd in that the pedal position sensor is in the body not at the pedal. So the throttle cable operates a pedal position sensor at the throttle body and then an electric motor operates the throttle butterfly. This is my interpretation of what a franchised dealer told me anyway.

I've ruled out the ABS / ASC interference now since on the return trip from the garage the ABS light was off once the usual check period was up but then the EML came on after about a mile and power was gone. Following 3 miles of dual carriageway painfully despatched at about 50 mph (eventually!) the EML fault cleared and we took off like a rocket for the final mile of the return trip.
This is what makes me think that the TPS is at fault since if patient you can get the revs up to 5000 rpm. If the throttle butterfly was stuck it wouldn't rev this high. However i guess it could be 'sluggish'! But then it is all one and the same part on this car anyway.

The code I was given today, which kept repeating after reset is P1580 (OBDII), P0505 (EUIII), Engine throttle mechanical fault (sluggish / stuck).

[Del]

This may be of some interest - it is starting to sound like a throttle sensor - I reckon INPA would absolutely pinpoint it for you - there is a list on this forum somewhere of members (who have it) prepared to offer their help.

http://www.zroadster.net/forum/viewtopi ... or#p343946

[Robert T]

The codes can only be as smart as the sensors that the ECU takes readings from - how do you tell the difference between a stuck throttle butterfly and a defective sensor that is telling the ECU the position of the butterfly. Annoyingly you need some in depth knowledge of what is being measured to trigger the codes - it could be one sensor value or it could be several - and I'm afraid that even with the right diagnostic kit, we are still lacking this knowledge.

@Del - that looks like a useful thread - had forgotten about that one.

Cheers R.

[therealdb1]

Thanks Del and Robert,

As I said TPS and MDK is effectively the same thing as it has to be replaced as a unit apparently but it is interesting to note that someone has disassembled a throttle body even though everything I have read says "don't do it! Don't even be tempted to operate it by hand!".

I checked the thread but as I suspected there's not too many diagnostic kits around rural Norfolk. Even my 'local' franchised dealer is 40 miles away!

I may well invest in an INPA tool as they do not seem that expensive alongside a throttle body and I like the fact that you can get real time outputs from the sensors which my current kit cannot do. If nothing else it should pin point which wheel sensor is causing the ABS warning to trigger sometimes. Not knowing which one of the four is the culprit is the reason I've done nothing about it for a year!

[therealdb1]

Well as you can imagine the law of sod has been applied.

My shiny new INPA gear arrived and after a frustrating evening yesterday just trying to install the software (shame that it cannot install anywhere other than the C drive) I hooked it up to the OBDII connector inside the car. It found the DME straight away and came back with the stored code 119 mechanical fault sticking throttle.

Impressed by the screens of real time sensor displays I started the engine and waited to spot the TPS misbehaving on the screen but of course the EML did not illuminate and the engine responded to the throttle pedal correctly! I cannot believe it the fault was reproducible at will until I connected the INPA!

I guess there is nothing for it but to whip out the throttle body and physically check it by leaving it connected to the ECU and operating the cable quadrant to see if there is any evidence of lag or sticking or I may just get a used unit which seem quite plentiful from £50 to £70 to bolt on and see if the fault ever returns.

I then tried to interrogate the ABS module but the software couldn't find this one. When I get a chance I'll have to connect to the Pacman under the bonnet as today was the first time I've ever had success with anything from the OBDII connector and fiddle some more as my INPA tutorial continues.

[Robert T]

Well that's progress of a sort.

Be interested to hear how you get on with the ABS/ASC/DSC module when using the round 20-pin connector (pacman isn't a bad name for it). I've heard a number of people saying they are having trouble connecting to theirs and it would be good to confirm whether the round connector does indeed have access when OBDII does not.

Cheers R.

Sent from my Galaxy SII using Tapatalk 2

[John Wilson]

I too have a 2 litre 2000 Z3. I used to have lots of trouble with the ABS light coming on and the car losing power as a result. Although it might not be the same in this case, I would really recomend regular cleaning of the wheel sensors no matter what any diagnostic equipment says. The first time you do it might prove difficult, as they are probably corroded into place and will need some releasing oil on them (not WD40), but after that they can be taken of and cleaned very easily. It's just one allen headed bolt for each one. They do clog up and stop working so you might as well do them now. Since doing this, I havent had the problem reoccur for about 3 years. While youre doing this, just clean the MAF sensor as well. Another easy and worthwhile job. You can get a spray to do this so you dont have to touch the wire bit (dont do it).

[therealdb1]

Thanks for the tips, John.

I have got an update on the ABS please see my next post as a reply to Robert.

I doubt very much if my MAF needs doing just yet since including the original it has had 3 different sensors in the last two months. The one currently fitted has done less than 10 miles!
We ought to stress not to touch the heated element when cleaning but otherwise a good idea.

[therealdb1]

Hi Robert,

Here's the under bonnet update.

I connected the INPA to the round connector and just to check connection I read the engine codes which came back the same as from the OBDII connector. I then searched for the ABS module which would you believe INPA found easily and gave me codes 148 and 49. These seem familiar, and if you can remember that far back, part of my OP was what do these code numbers mean? Well thanks to INPA I now know that 148 is something to do with the CAN presumably ASC signals and 49 is rear left wheel sensor. I don't know what happened to 50. This may have accidentally got cleared with the variety of diagnostics gear that has gone onto the car in recent months. I suspect this is another wheel sensor code and a combination of 49 and 50 have caused 148.

Buoyed by this success I cleared 50 events of the power reset error on the EWS module just to check to see if I could actually clear codes. I am going to have to do throttle adaptions shortly!!!

So in summary it seems that on these intermediate cars only certain data is available at the OBDII connector. In fact my generic OBDII hand held reader gets nothing from the OBDII socket and I have to use an adaptor and connect it to the Pacman. My PA software came with a circular connector anyway, and INPA gets DME data only from OBDII but ABS, EWS etc seem to be available under the bonnet.

This is indeed progress!

The next plan is to fit the replacement throttle body I have ordered and tinker with my existing one on the bench to see if I can find out what has malfunctioned, and also follow John's suggestion of cleaning the wheel sensors. Because this ABS fault is intermittent I suspect that they are either clogged or the connector is not making all of the time but at least I have a corner to start at now!

[Robert T]

Well that sounds like good progress. I do like INPA, and it is interesting exploring what it can do. You wouldn't be able to do me a listing of the modules you can access through both ports would you? I'll add the data to the spreadsheet in this post, which will hopefully build a proper article in the future.

Cheers R.

[Brian H]

Apologies therealdb1,not meaning to hijack this thread, mods please move if required!

I have been looking in to the modules available for OBD (round connector under bonnet) and OBDII (under dashboard), the diagram below gives some insight in to the modules available, it is early days for me but from what I can understand: -

There are three TX Data lines and one RX Data line, OBD gets all three TX Data lines whilst OBDII only gets one. Three of the modules require both a TX and RX data line, the Tx Data lines in the OBD port are on pin numbers 1, 17 & 20 whilst the Rx Data line is on pin 15.

The OBD port has access to all the modules as it has all Tx & Rx data lines, for reference the OBD port in the diagram is called D100 Data Link Connector

OBD Module access



There is a link in the OBD cap that bridges in 17 to pin 2, Pin 2 then feeds the OBDII port with that specific TX data line, therefore looking at the diagram below, OBDII has access to the transmission control module and the engine control module.



There are a couple more diagrams that are useful so will maybe post in a dedicated thread once I have my head round it a little more.

[Robert T]

Brian, this would be more appropriate in my module access thread. I'll move the posts later when I have proper net access.

The adapter cable from BM Technic shorts some pins together, so this may be giving access to more data lines - it is after all only an OBDII to USB adapter.

Cheers R.

Sent from my Galaxy SII using Tapatalk 2

[therealdb1]

Hi Brian,

That's a useful technical insight into what is going on and why connection through OBDII is so limited.

Robert,

Yes I can give you more information but I'm away on business for a week from tomorrow so it will not be immediate. I hope to get the faults fixed and an MOT when I return so the diagnostics shall be hooked up again then and I shall make some notes and forward them.

Cheers

Chris

[Mike Fishwick]

I always thought that the M52TU engines such as the 2 litre do indeed use a cable-operated throttle, the motorised part of the throttle unit being used by the ASC system.

Likewise, surely the 2 litre is not fitted with DSC?

You seem to be getting yourself more and more confused and complicated - get back to treating it as a car and not a computer!

For example, have you considered that the fuel pressure may be low, due to a blocked filter or degraded fuel? Siting in a garage for a while does not damage airflow or cam sensors . . .

[therealdb1]

Hi Mike,

Thanks for your input.

My understanding is that the 2 litre engines do have a cable to the throttle body but it is not mechanically connected to the throttle butterfly. It only operates a potentiometer which in turn instructs the control unit to send a signal to the butterfly motor with position information. This can be over-ridden by the ASC at the control unit. It is in effect a fly by wire system but for some reason BMW chose to put the pedal sensor on the throttle body. On the M54 the sensor went on the pedal which is the logical place for it to be.

No one has suggested that the 2 litre has DSC. It has ASC but the topic has broadened somewhat since the OP in a way that, I believe, benefits all of us. As Robert suggested part of this thread shall be moved to a more appropriate post as he gets time and data to put it together.

Unfortunately it is a fact of life that cars have become more computer orientated since the 1990's and they all now come with a plethora of sensors. On board diagnostics are provided to assist with fault finding but as Robert said earlier the diagnostics are not infallible and can give red herrings. I know I replaced the cam sensor for no reason but the MAF was faulty; original one car does not run, new one car runs.

It's a good point about fuel but the car has had two full tanks of fuel through it since the initial non-running problem and I struggle to believe that fuel pressure problems whether pump or blockage induced could be so intermittent as to go from full power to limp home and full power again in a matter of minutes. To me the symptoms are typical of an electrical fault.

[Mike Fishwick]

It takes a big leap of faith to decide your intermittent problem is due to an electronic problem! Most electronic failures are stable - they never get better - whereas mechanical or fuel problems can come and go.

The fact is that your engine worked again after you had churned it around a little, and I cannot believe that both the airflow sensor and the cam sensor were faulty.

As matters stand, you seem to be chasing your tail, and would do better to try some cheap and logical fault-finding, rather than making a decision and then trying to back it up. A computer is all very well, but it cannot tell you about a lot of things.

Your symptoms could easily be those of intermittent fuel starvation, induced by a blockage in the fuel filter, or a problem withthe fuel pressure regulator. A fuel pressure test may therefore reveal something, and a new filter is probably overdue anyway. As the filter will not pass water, it may have succumbed to an accumulation of moisture, which has seperated out of the fuel during your long lay-up.

And - the M52TU engine has its throttle operated directly by the cable, the other end of the spindle being connected to the TPS. The electronic throttle operation came in withthe M54 engine, as used on the 2.2 and 3 litre models.

Good luck!

[therealdb1]

The latest update.

I decided that the most likely cause of my problem was either the MDK or the interconnection between this unit and the DME being intermittent. Looking on ebay there were plenty of pre-owned MDK's to choose from so I picked the one that looked the cleanest and once it arrived spent a pleasant couple of hours in the sunshine swapping the throttle body. It was a much simpler job than the last one I undertook on a Jaguar XJR which took a whole weekend!

The car appears to drive fine and the codes have not returned but only time shall tell if this has been a permanent fix.

Incidentally, for future reference Mike is correct in that the cable does operate the butterfly via a spring allowing the ASC to take over if it needs to. I was led up the garden path a little by the franchised dealer but then I presume that they are talking about current models more often than 13 year old technology.

Whilst I was in the groove I thought that I would follow John's suggestion about cleaning the ABS wheel sensors. I do not think these had been out since the car was built and it's pretty rusty underneath. The Allen bolts came out without issues so I thought that I was winning but after about an hour of cursing the nearside rear sensor was in my hand and it was caked in various bits of magnetic material. I'm not surprised it struggled to pick up pulses. I cleaned the sensor up and cleared the hole in the upright of rust and added a little silicon grease (my favourite lubricant!) before refitting. The offside was more of a challenge and the sensor snapped off in my attempts to get it out. I ended up having to drill the coil section out of the upright so there is no saving that one. Of course no one in Norfolk has one of these on the shelf so it is back to waiting for Postman Pat to bring me a shiny new sensor to bolt in before I can head to the MOT station. I think that I shall leave the front sensors alone for now as they were not inducing any codes so I presume that they are ok at present.

Robert I will get the list of available modules to you shortly but I was away all last week and am away again until early next week. As you can understand getting the car running and through an MOT was my priority while briefly at home.

[therealdb1]

Robert,

I've added the module availability on my car to the appropriate thread as promised. It really substantiates Brian's description of how the OBD is configured on the Z3.

With the replacement throttle body and two new rear wheel sensors fitted the car is showing no warning lights at present and is booked for MOT Monday so fingers crossed.

Thanks for your help during my fault find.

[therealdb1]

Car returned today with a year MOT and no advisories.

It seems to cruise better now too but not convinced if this is the replacement MDK or just psychological.

Sorted!!!