Error 4121 and crazy stuff

I have had intermittent (once in a while; many long periods without a problem) CEL's for the last year with shut down of cyl 1-4. Usually an engine shut off and immediate re-start would fix it. Now I have permanent shutdown of 1-4 and so far no activity has changed it. The car is now cold and I should expect the cat overheating signal should be gone and it should fire up properly but that is not the case. I have checked the connections on the crank sensors and cleaned them. Any suggestions? Where are the ECU's for the cats on a Mondial? Any easy way to check for a plugged cat?

 

Thanks much I'll have a look.

 

I disconnected both exhaust ECU's and started up but still 1-4 is not firing and there is no CEL. I cleaned the connectors but no improvement. I guess I need to look elsewhere? Can the Crank sensor failure cause this? Is there a crank sensor for each bank since there are two of them. Maybe I should also look at something stupid like the coil,-spark plugs are new. Thanks for any comments.

 

Am I correct in thinking that the placement of the Exhaust ECU in the Mondial T is much better than the 348 as they are more or less protected from the elements? Or do I not understand the 348?

 

I have never had slow down lights. Only CEL's. Would you think that if I had real over heating of the cats that I would get a slow down light rather than a CEL?

 

No change after switch. 1-4 still dead.
Checked resistance on MAF's spot on.
Will look at O2 sensors tomorrow.
And will try to see if spark is arriving somewhere.

 

No. Will do. I have switched the ECU's; no change. I have ordered O2 sensors and I have the KIA crank sensors. I will probably change all of those out as it's all almost 21 years old.
Thanks much for your help.

Randall

 

I have dismounted and cleaned every connector I could find in the ECU area as well as the Engine. I do not find a ground connection to the cam covers. I have changes the crank sensors and no change. I checked the continuity of the thermocouples and they are not open.
I have attached a photo of a plug (with the white wire loop); could someone confirm the function of this? Is this the diagnostic plug for the Mondial T?
Thanks again for your help.
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Thanks much. I feel quite stupid to have overlooked those. Thanks much for the help. I will get on those tonight. Where is the other end; is there another end?

Thanks again for the patience.

 

I have a reserve new ignition module and will replace it on the 1-4 side to see what happens. If I understand correctly, the 4121 error shuts down the fuel pump on that side. Does it also shut off the spark?

 

I have found a white greasy paste on the back side of the ignition module. Is this anticorrosion treatment? Is it original? These look like the original pieces? I thought this interface was for contact with what looks like a heat sink. Any kind of anti-corrosion paste might insulate heat transfer and not do its job? Kind regards.

 

OK thanks very much. Tomorrow. Kind regards.

 

All grounds have been cleaned and treated. Unfortunately, I cannot find my reserve ignition module and have had to order again! crazy! In any case the work is on hold until the O2 sensors and ignitors arrive. Thanks again.

 

Are you referring to the relays next to the ECU's in the trunk? Which one is the fuel pump relay or where is it found? I assume these are for the MOTRONIC 2.7 ecu's. Thanks.

 

I have not checked on either footwell in my Mondial T . I guess tomorrow morning we will discover what's under the carpets. Thanks again.

 

The location of the fuel pump relays are shown on page C3. They are located next to the Exhaust ECU's and next to the Motronic ECU's. I have checked the fuses and they are ok. I will switch sides and see what happens. Thanks again for the outstanding support.

 

New crank sensors, new O2 sensors, new ignition module for the 1-4 bank. Nothing. Fuel pump and injector relays to be replaced on monday. I am now thinking coil? It was replaced recently. I would be surprised but it wouldn't be the first time. I always think the problem is more complicated than it turns out to be.