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?