Question: Can an EZL unit store noted faults in memory?

Had the car in the garage a few weeks ago and they hooked up the reader to check out any recorded ignition system faults (think it’s black wire to pin 1, yellow to pin 8 and red to pin 16). With the engine off the reader indicated error code 17, which when looked up on the fault code table = “Crankshaft position sensor defective (L5)”. Based on this I had it replaced.

What’s concerning me though is last week I was on www.AllDataDiy.com checking something out on my model (it’s a 124.061 with a 104.980 engine) and it states there that the EZL control unit (controls my ignition system) “….does NOT have memory malfunction capabilities, so only faults that are present while the test is being conducted will be indicated.” It then describes a number of steps to run through to ‘exercise’ the running engine with the reader connected, so as to find/record faults.

When I subsequently spoke to the garage (‘experts’ on old Mercs) they said they’d never heard that you needed to do a ‘live’ test to pull ignition faults, and I don’t think they really believe me.

Who’s right then: the garage or the AllData info?. If the AllData info is correct and there is no stored fault capability in the EZL unit, why did a code 17 come up with the engine off? More to the point, have I wasted £200 on a new crankshaft position sensor?

EZL/AKR or DI Module, check out my web page, MENU #5.

Yes, it stores faults and can incorrectly store faults that are not really there!! In fact, what started me to 'write' my "Mercedes S500 Cpe" page was the DI Module.

About a year or so after purchasing the car, the CE light came on and the fault was, you guessed it, the same as yours: Crankshaft position sensor defective (L5).

I did NOT replace it since it measured about 860 ohms and produced a valid signal. Remember, if the CKS sensor is really bad, the car won't run!.

The problem was located in the DI Module's fault memory. To explain this think of it as having a bad memory location where a "bit" is stuck on that just happens to indicate a bad CKS sensor when in actuality, it was not bad.

I found a used DI Module from a junk yard in NYC for $200! It's still in the car as of today.

This is not to say that you really didn't have a bad CKS but if the car was running, it would be hard to explain.

__________________
Regards . . . . JimF
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'94 S500 Cpe

Visit my Mercedes Web Page

Thanks for the reply Jim.

That does leave me slightly mystified as to why the literature at Alldata should state that the EZL/AKR (injection controller) cannot store faults - note, it does (correctly?) state that the MAS (engine management controller) and CIS-E (injection controller) can store faults. Is it possible that it depends on the age/model of the car - i.e. version of EZL/AKR unit, or are they simply misinformed (I thought their info came straight from Merc HQ in Germany)?

The reason for my visit to the garage was to try to fix an ongoing intermittent rough idle problem that seems to be very common on the M103 and M104 engine. Needless to say the CKS sensor replacement hasn't solved it! Based on what you said, might that point to the EZL/AKR unit being the root cause of my idle problem, or do you think a potential memory fault (storing #17 needlessly) is just a small 'characteristic' of my unit that I should live with?

Cheers,
Neil

illuminated, then I'd live with it!! But in CA cars, DTC#17 will light the CE lamp, so it's hard to live with that fault since the car will never pass CA 'smog' tests. I had to replace mine so it would pass smog.

The DI Module, for my car, reflects STORED and ACTIVE codes: that kind of explains itself, doesn't it? Now maybe there's a difference in the Euro vs American cars??? With and without DM module??

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

Visit my Mercedes Web Page