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Unread 04-04-2013, 05:05 PM   #1
billyblooshoes
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First Problems w/ New 5.9

-well, i guess im officially part of the club now. not too upset though as i knew the inevitable regular issues would arise. had a CEL come up yesterday and i got it scanned today. here's what came up:

P0505: Idle Air Control System
P0141: O2 Sensor Heater Circuit Bank 1 Sensor 2
P0138: O2 Sensor High Voltage Bank 1 Sensor 2 (this came up twice)

-i briefly looked up the codes, but i guess im just looking for some feedback from you guys as to what the problems are definitively, and/or what i should replace. im assuming these are common codes the ZJ's throw.

-i also noticed a relatively strong odor of coolant while the car was running today, but i dont see any pooling under the car. the VIC is showing coolant sensor bad, but i was under the impression this was a false reading.

-the MAIN issue i noticed today was actually very alarming. i was doing around 50mph, and the car in front of me hit their brakes pretty hard. i was forced to hard brake, and as i stomped the brake pedal, the car pulled (more like swirved) to the right pretty drastically. it was somewhat scary. i successfully replicated this three more times, so im pretty worried about it. my theory is that for some reason one of the front brakes is not engaging fully, thus causing the vehicle to pull to the right under braking. thoughts?

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Unread 04-04-2013, 09:16 PM   #2
billyblooshoes
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for the codes i am figuring on buying two new O2 sensors and a new IAC. might as well just replace those.

my main concern is the swerving when braking though, any insight on that guys?

EDIT: second thought, ill try cleaning the IAC first. after searching around a bit it seems that they can become extremely gunked up and i did notice my jeep was idling a little high today (around 1k rpm)

Last edited by billyblooshoes; 04-04-2013 at 09:39 PM..
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Unread 04-04-2013, 09:43 PM   #3
Bigtniner
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Anybody correct me if i am wrong, but the only thing that the Downstream o2's do are determining whether your cat is in working order or not. I couldn't tell you when mine were last hooked up on my niner as it was not plugged in when i bought it. SO... you could either put up with the cel or buy a new o2 or cat depending on the condition.
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Unread 04-04-2013, 09:45 PM   #4
billyblooshoes
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Quote:
Originally Posted by Bigtniner View Post
Anybody correct me if i am wrong, but the only thing that the Downstream o2's do are determining whether your cat is in working order or not. I couldn't tell you when mine were last hooked up on my niner as it was not plugged in when i bought it. SO... you could either put up with the cel or buy a new o2 or cat depending on the condition.
thanks for the input. according to the previous owner, the cat is relatively new. the sensors are cheap so im just going to go ahead and replace both of them.
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Unread 04-05-2013, 07:11 AM   #5
gs69350
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Check the suspension. Pulling to the right under braking could be due to worn out control arm bushings, ball joints, steering. If it doesn't pull under regular braking, i'd suspect the suspension components first.
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Unread 04-05-2013, 07:51 AM   #6
PolkaPower
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I have read that the DS o2 sensor monitors the cat and provides information in conjunction with the US sensor.
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Unread 04-05-2013, 07:52 AM   #7
gs69350
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Oh ya... Welcome to da club!
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Unread 04-05-2013, 01:51 PM   #8
Candymancan
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My 5.9 pulls as well when i brake really hardand pulls to the right just like yours... Never figured out why it does that.. My guess would be the shocks.. My control arms are brand new, and my suspension as far as ball joints and stuff are in good shape.. The shocks are original... Either that or the Tires are squishing under the weight from hitting the brakes hard i dunno..
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Unread 04-07-2013, 06:32 PM   #9
billyblooshoes
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so i went to pull out the IAC today and it seems its pretty new and it was clean. the previous owner had replaced it as i found the box for the new one in the trunk. the only thing was he forgot to put the o ring on the new one, so i threw that on there. any chance thats what could have been throwing the code for it?
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Unread 04-08-2013, 04:57 PM   #10
Candymancan
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The idle air control valve has nothing to do with 02 sensor codes.. at least i am 80% sure on that..

Sounds to me like the previous owner cleared the codes... and sold you a Jeeps with check engine problems.. clearing the codes make them go away for like 20-100 miles before the computer relearns itself
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Unread 04-08-2013, 05:04 PM   #11
billyblooshoes
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Quote:
Originally Posted by Candymancan View Post
The idle air control valve has nothing to do with 02 sensor codes.. at least i am 80% sure on that..

Sounds to me like the previous owner cleared the codes... and sold you a Jeeps with check engine problems.. clearing the codes make them go away for like 20-100 miles before the computer relearns itself
Yes I am aware of that, but the first code I posted is for the idle air control valve.
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Unread 04-08-2013, 05:15 PM   #12
1shotwonder
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Have you checked the simplest thing for the braking prolem? That being making sure your all your tires up up to correct psi? Have you gotten an alignment? Sound like the one pad might be catching harder then the other one too...
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Unread 04-08-2013, 05:43 PM   #13
Bannerman53
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I would go ahead and replace the IACV, and yes the downstream O2 sensor only provides info to the for the cat, it doesen't make it run richer or leaner.
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Unread 04-08-2013, 07:11 PM   #14
PolkaPower
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Quote:
Originally Posted by Bannerman53 View Post
I would go ahead and replace the IACV, and yes the downstream O2 sensor only provides info to the for the cat, it doesen't make it run richer or leaner.
Not according to Kolak. http://www.jeepforum.com/forum/f13/c...ensor-1124945/

Here is another post from JF talking about it as well. I thought it only monitored the cat to but apparently it influences the upstream sensor too. http://www.jeepsunlimited.com/forums...d.php?t=408828
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Unread 04-08-2013, 07:22 PM   #15
1shotwonder
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Why go after the IAC first? The question should be, is the OP's engine showing signs of a bad IAC? Maybe its just me, but I would prioritize brake issues before an IAC.. I mean after all the brakes are what make you stop... Without them working properly you might just be SOL one day...
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