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General Forums => The Mess Hall => Topic started by: jcguin on August 28, 2006, 07:25:08 AM

Title: Trouble Codes 12, 41, 72 is there a link?
Post by: jcguin on August 28, 2006, 07:25:08 AM

Friday afternoon on the way home from work I stopped at a light, then took off and suddenly my check engine light came on.

There was no change in power or sound, nor any gauges out of normal range so I continued home.

I pulled up the codes and found the following:

12  Battery Disconnect  = Direct battery input to PCM was disconnected
                                      within the last 50 Key-on cycles.

41 Generator Field Not Switching Properly  =  An open or shorted condition
                                                                  detected in the generator
                                                                  field control circuit .

72  Catalytic Converter  Efficency Failure   = Catalyst efficiency below
                                                                  required level.

Does anyone see a link here?  My jeep has over 176k on it so I know it probably needs a new cat.  Actually I think that may be part of my power (or lack there of) problems.  But I dont see why I would suddenly get the other two errors.


Actually the 12 code I can understand, cause it supposedly wont make the check engine light come on as soon as it alarms, so that one could have been there all along, but the 41 and 72 should have as soon as it met the alarm condition.

Any thoughts?

Title: Trouble Codes 12, 41, 72 is there a link?
Post by: Jeffy on August 28, 2006, 01:18:14 PM

12 and 55 are normal codes.  33 is one that ususally pops up also.

Cat's are warrantied to last something like 5 -7 years and 50-70K miles.  Cat's should be changed at least every 10 years though so it makes sense that it's throwing codes.  (BTW: this is only found on ODBII vehicles)

For 41, I'm guessing they're talking about the Alternator.  Have you been having any charging problems?

Title: Trouble Codes 12, 41, 72 is there a link?
Post by: jcguin on August 29, 2006, 07:08:57 AM

I figured I needed to change out the cat, it was already on my to-do list.

As for the alternator, I have not been having any problems.  I had not even considered that for the code 41, I hope that is all it is.  I was thinking that was a PCM issue, not a charging issue.  Alternator would be a breeze financially compared to the pcm.

Title: Trouble Codes 12, 41, 72 is there a link?
Post by: Jeffy on August 29, 2006, 11:35:36 AM

"Open or short in the generator (alternator) field control (regulator) circuit. This indicates a problem with the charging circuit and the fault is set when the battery voltage from the ASD relay falls below 11.75 volts. Wiring, connectors, fuses, and the ASD relay should be checked. A shorted battery cell can also trigger this fault."

Title: Trouble Codes 12, 41, 72 is there a link?
Post by: jcguin on August 29, 2006, 02:07:35 PM

Thank you guru of all things "jeepish".  Your depth of knowledge shames us all.  


I'll check those things out and see if anything is truly out of whack.