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EZL fault code 20

Carl1886

Member
Member
Hi I’m diagnosing a rough running issue in my 1992 500 E and tracked it down to being a bad coil for the bank two distributor. However I have fault code 20 in the EZL module just curious what this means. Is it a bad control unit?
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N1/3 I have listed as the EZL I.E. "No CAN data transmission with DI control module (N1/3)" and that would be a perfectly reasonable code to get if one of the coils is bad, "the computer sees that the car is not firing on one bank, therefore the EZL must be at fault". The diagnosis system on our cars is not very sophisticated.

If the car runs as normal with a new coil, reset the code and recheck in a week or so.
If the car will not be fixed after a new coil I'd try the following:

If you have a spare EZL, try swapping it first, if not or if it doesn't solve the issue:

Check the connections on the EZL ensuring all is in place correctly. The EZL rarely fail, and when they do you end up with either a four popper one side, or no go at all. Is the "rough running" that one bank is not firing, I'd be suspicious about the coil and/or EZL. If the rough running is not consistent with one bank or the other, I'd look further. Try to eliminate with spark plug wires etc to know.
 
If code #20 will not clear, and/or keeps recurring immediately, the FSM says to replace the EZL - see below. Click here for the full PDF that screenshot was taken from.

Seems like code #20 indicates the EZL will no longer properly store/display fault codes, although it may still function correctly. If you are interested in buying a known-good/tested replacement EZL, drop me a line (click "start conversation").

In the meantime, replace BOTH coils with new Bosch, and closely inspect the rest of the secondary ignition system as doolar mentioned above. In particular check for oil leaking from the cam solenoids and running along the bottom edge of the distributor cap, along with checking for liquid on the back of the insulators. Either of these problems can cause intermittent ignition issues. Adding vent slots to the caps is generally recommended (click here for details) but if there's an oil leak, that has to be remedied as well.

BTW, welcome to the forum!

:welcome4:

1729257263454.png
 
If code #20 will not clear, and/or keeps recurring immediately, the FSM says to replace the EZL - see below. Click here for the full PDF that screenshot was taken from.

Seems like code #20indicates the EZL will no longer properly store/display fault codes, although it may still function correctly. If you are interested in buying a known-good/tested replacement EZL, drop me a line (click "start conversation").

In the meantime, replace BOTH coils with new Bosch, and closely inspect the rest of the secondary ignition system as doolar mentioned above. In particular check for oil leaking from the cam solenoids and running along the bottom edge of the distributor cap, along with checking for liquid on the back of the insulators. Either of these problems can cause intermittent ignition issues. Adding vent slots to the caps is generally recommended (click here for details) but if there's an oil leak, that has to be remedied as well.

BTW, welcome to the forum!

:welcome4:

View attachment 199880
I’ve replaced plugs(non resistor Bosch), wires, caps, rotors, and insulators along with the coils. The misfire I had is gone. It’s just that fault code stays in memory and won’t clear.
 
I’ve replaced plugs(non resistor Bosch), wires, caps, rotors, and insulators along with the coils. The misfire I had is gone. It’s just that fault code stays in memory and won’t clear.
Excellent! I'd still add the additional slots to the brand-new caps as described in the thread linked above. It's a consistent issue with these distributors, for reasons that aren't entirely clear.

If the engine is back to running 100% normally, you could choose to ignore the EZL code #20, just keep in mind that other fault codes may not be stored or displayed. First I've heard of this particular failure mode, it's not common.

:klink:
 
Excellent! I'd still add the additional slots to the brand-new caps as described in the thread linked above. It's a consistent issue with these distributors, for reasons that aren't entirely clear.

If the engine is back to running 100% normally, you could choose to ignore the EZL code #20, just keep in mind that other fault codes may not be stored or displayed. First I've heard of this particular failure mode, it's not common.
Thanks. It sure is an odd problem. I get the normal ckp fault when the engine isn’t running and tested if it would set a fault if I pulled a plug wire and it set a misfire fault for that cylinder. I’ve got a friend with 500 SL I’ll try to borrow his to see if the fault goes away.
 

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