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Any good diagnostic tools available?

Basic needs related to restoring a 6er including
Electronics, Bodywork, Welding, Painting, Engine Swap, etc
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Any good diagnostic tools available?

Post by Da_Hose » Sat May 19, 2018 9:15 pm

Hey everyone,

I have been working on my 6er for many years, and always and have been wondering if there is a genuinely good diagnostic tool out there for us E24 owners to use.

I also have a 2006 530XI in the household, which is pretty much a rolling computer. To work on that car, I built an INPA WinKFP based computer, and it is awesome to have. Other than good old multimeters, and such, has anyone found diagnostic tools worth having? I looked at the Peake R5-FCX tool sold all over the place, but I can't find a single example of someone using that tool to do work on a 6er. Has anyone on the forum tried using the Peake tool, and able to report what kind of results you got? Is it worth the money?

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Re: Any good diagnostic tools available?

Post by Brucey » Fri Jul 13, 2018 5:55 pm

BITD when engine diagnostics was in its infancy, some cars (BMWs and SAABs amongst others) had their own proprietary interface which allowed garage mechanics to carry out adjustments and measurements more easily. Typically this consisted of an analogue meter (which could be set to measure various things using front panel controls) a timing light output and some flashing lights in a box. The unit also allows the engine to be started and stopped remotely, for example. I still have one of these units (made by a third party) with a SAAB interface lead on it. I also have a Snap-On branded meter that can be made to do similar things but it doesn't have an interface lead per se, it is more like a posh multimeter in that respect. The BMW diagnostic port (as found on BMW models like E24) was born in this era

BITD when carbs and contact breakers were the norm these tools were invaluable. Even when L-jet was introduced you could use one to usefully check idle speed, dwell angle, ignition timing variation and a few other things besides.

But once Motronic was the norm, there was little need for any of these things; 'analogue' type errors basically stopped happening, i.e. the system either worked or it didn't, and the measurements so afforded by various tools of that type were not that helpful any more.

Later motronic versions of E24 have some built-in diagnostics (beyond a simple warning light) eg I think you can get flash codes out of post 6/87 vehicles but in reality these are of limited value; they are nowhere near as sophisticated as later built in diagnostics became.

So IMHO on E24 beyond short cutting flash code reading (later models only), there is very little for a modern diagnostic system to do. There is some value in having a box of tricks that plugs into the diagnostic port; you could configure it to reset the service indicators, start and stop the engine remotely, that kind of thing. But beyond that for troubleshooting early Motronic systems the DMM is the weapon of choice, and if you have an oscilloscope (and know how to use it) this can be handy too.

However this conversation has reminded me of one thing; I have long intended to 'characterise' an E24. In other words, using simple measuring tools, what does 'normal' look like anyway? Some of these things are in the workshop manual but many others are not. Places where this could be useful include;

- oscilloscope traces of coil signals and injector signals
- oscilloscope traces from crank sensors (all three)
- ditto from ABS sensors

- accurate plots of CTS and ATS values with changing temperature
- ditto TPS sensor with throttle angle
- ditto AFM with flap angle
-advance curves with engine rpm and injector duty cycle/temperature

- ICV signal vs opening angle

- sound recordings (e.g. taken using a mechanics stethoscope) of all 'normal' engine running noises at various points in the engine and ancillaries

such information would be very useful in diagnostic work, if you don't have a 'known good' example to go from. For instance a couple of years ago myself and some others more or less confirmed a diagnosis of a duff camchain on an M30 engine using a mechanic's stethoscope. We had a good M30 to act as a comparison; without that (or recordings) we'd have been in the dark for sure.


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Re: Any good diagnostic tools available?

Post by nick88highline » Sat Jul 14, 2018 12:22 pm

I have got the Peake tool, but it only works on the very last E24s with the large round diagnostic connector.
It will pick up the limited list of fault codes that Motronic 1.3 will output.
Here is the list for interest:

DME control unit selftest
Electrical fuel pump relay
Idle speed actuator (open)
Evaporative purge control valve
Air flow meter
Emission (lambda) control
Check engine lamp
Fuel injectors: 1, 3, 5
Fuel injectors: 2, 4, 6
Idle speed actuator (close)
Oxy sensor heating relay
Oxy sensor
Vehicle speed signal not present
AT kick-down prevent solenoid valve
Control unit supply
Automatic stability control/DWA
A/C compressor
Idle CO potentiometer
Intake air temperature sensor
Coolant temperature sensor
Engine drag torque control (MSR)
Ignition timing intervention
Idle switch
Full load switch
Torque convertor clutch
Unspecified DME output stage

I'm not convinced it's perfect, for example if you un-plug the AFM from the car and drive it around the fault code reported is not "Air flow meter" #-o
It can of course reset service lights and so on, and you never know, it might be useful one day...
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