Diagnosic code 12 (recently disconnected battery), any ideas?

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Aug 22, 2010 | 11:08 AM

loligator

Thread Starter

Member

Joined: Apr 2009

Posts: 190

Likes: 1

From: South Jersey

Year: 1996

Model: Cherokee

Engine: 4.0

Diagnosic code 12 (recently disconnected battery), any ideas?

Hey all,

So my XJ (1995, OBD I) is putting out two codes, 12 and 21. 12 is battery/computer recently disconnected and 21 is a malfunctioning O2 sensor. I haven't recently disconnected the battery so I'm not sure why 12 is being thrown. Any one have an idea as to why 12 is being registered in the computer? Could a bad O2 sensor make 12 register?

Aug 22, 2010 | 03:16 PM

b4wheeler

Junior Member

Joined: Aug 2010

Posts: 56

Likes: 0

From: Pasadena, Md

Year: 1996

Model: Cherokee

Engine: 4.0

Recent means within the last 50 key cycles...

Have you pulled any fuses lately???????

Aug 22, 2010 | 03:35 PM

sv41878

Senior Member

Joined: Jun 2009

Posts: 670

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From: Central Pennsylvania

Year: 1989

Model: Cherokee (XJ)

Engine: 4.7 H.O.

My friend had that issue, turned out to be a bad ground to the PCM.

Aug 24, 2010 | 04:45 PM

loligator

Thread Starter

Member

Joined: Apr 2009

Posts: 190

Likes: 1

From: South Jersey

Year: 1996

Model: Cherokee

Engine: 4.0

thanks for the replies guys

it's definitely possible i disconnected the battery within the last 50 starts. i'll worry about it if it keeps coming back after i take care of the o2 sensor. least i know if it keeps up, i can check the ground to the PCM.