Check engine. Help please!

[96xj-A-skwad]

Hello,
96 xj 4.0 auto trans stock. Bought about a month ago. No cat, o2 sensor held up with zip ties. Never had the check engine light before. Today I drove my normal 25 min commute and the light came on. It was snowy and wet out.

Read the light sequence, then got it read at advance auto.

12-battery or PCM recently disconnected
25- idle air control solenoid shorted or open condition
21-o2 sensor

P0505- idle air control sys
P0138- o2 sensor bank 1 sensor 2

What should I start looking at here?
Anything urgent?

Also probably not related, but starting today I also get a weird clunk or thump from the rear after a bump.
Guessing exhaust, shock mount or bushings.

Help!

Thanks all

 

[96xj-A-skwad]

Edit----just crawled under there in the snow..... Previous owner apparently Jerry rigged the top shock mounts on both sides. One had 3screws init instead of the two stock bolts. The other side was welded..... By a blind person aparently. I'm 90% sure the weld broke free and that's why I'm clunking

 

[Ecomike]

Sensor is after the missing Cat. IAC Idle Air Controller is on the throttle body, it controls the idle air flow rate. Look for damaged wire, O2 wires perhaps in the harness?

 

[96xj-A-skwad]

Its not likely the two are related right? Being as one is under the hood and the other underneath the jeep.

 

[Matthew Currie]

The #2 oxygen sensor is not entirely necessary for good running, and when it starts to age it may go on and off again a number of times. I had a lot of instances of this on my 99 when it got over 250 thousand miles, and it seemed to depend a little on the gas, and also reappeared only after hot restarts. If you're on a tight budget I'd work on the idle air first, and ignore the O2 at least for a while, especially if when cleared it does not come right back on.

 

[Ecomike]

He has no Cat, so the second sensor is not needed.

 

[Ecomike]

Its not likely the two are related right? Being as one is under the hood and the other underneath the jeep.

Correct, Unless the wiring in the harness got damaged by a short underneath in the O2 wiring and it damaged the IAC wiring!!

 

[96xj-A-skwad]

Thanks for all your help guys. I ignored the light for a bit because I have the bigger problem of the shock mount weld coming apart.

The CEL went out yesterday, so I'm going to bet it had something to do with the wet weather and wiring.

Now to re weld the shock, until I get my lift kit