# 99' Jeep Cherokee Sport **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** cherokee, sensors, jeep\ **Created:** [March 11, 2010, 5:42pm UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919 "2010-03-11T17:42:55Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![recoiled](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@recoiled](https://community.cartalk.com/u/recoiled)\ **Post date:** [March 11, 2010, 5:42pm UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/1 "2010-03-11T17:42:55Z")
My car has faulty intake and outake O2 sensors. Are these difficult to replace. Do I need them. The jeep is a beater - with a smashed in front from a quarry accident and I don’t want to throw too much cash at it. 120,000 miles, and otherwise running smoothly. ---
**Author:** ![missileman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/missileman/32/1366_2.png) [@missileman](https://community.cartalk.com/u/missileman)\ **Post date:** [March 11, 2010, 5:56pm UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/2 "2010-03-11T17:56:22Z")
I would replace them. Get a couple of estimates from local mechanics and then decide. ---
**Author:** ![recoiled](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@recoiled](https://community.cartalk.com/u/recoiled)\ **Post date:** [March 11, 2010, 6:00pm UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/3 "2010-03-11T18:00:51Z")
$386.00 and $402.00 ---
**Author:** ![ignoramus9](https://avatars.discourse-cdn.com/v4/letter/i/d07c76/32.png) [@ignoramus9](https://community.cartalk.com/u/ignoramus9)\ **Post date:** [March 11, 2010, 6:02pm UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/4 "2010-03-11T18:02:30Z")
replace em because you could get a hot seat if you dont. The o2 sensors regulate the fuel mixture so that your catallitic converter does not overheat. How do you know they are faulty anyway? ---
**Author:** ![recoiled](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@recoiled](https://community.cartalk.com/u/recoiled)\ **Post date:** [March 11, 2010, 6:40pm UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/5 "2010-03-11T18:40:03Z")
Solid check engine light had me go into a Firestone - they pulled the codes and said that both of the sensors are misfiring. ---
**Author:** ![geeaea](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@geeaea](https://community.cartalk.com/u/geeaea)\ **Post date:** [March 12, 2010, 12:34am UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/6 "2010-03-12T00:34:38Z")
Go to Advance Auto or Auto Zone and have them read the codes and write them down. O2 sensors don’t misfire and I would have a real hard time figuring BOTH of them going bad at once. The lower 02 isn’t even needed for A:F regulation. It only checks catalytic efficiency. $65-$70 and U-DO-IT. ---
**Author:** ![recoiled](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@recoiled](https://community.cartalk.com/u/recoiled)\ **Post date:** [March 12, 2010, 1:25am UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/7 "2010-03-12T01:25:28Z")
I got the codes from Firestone, and both are off. I very much appreciate you’re reply. I did do a little more homework and it looks like the O2 sensors have about a 100,000 mile life expectancy, so that I got 120,000 makes me kind of happy. I do think I’ll end up doing this on my own. My only worry is that I burn the converter while I’m being stubborn about figuring out my best course of action. ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [March 12, 2010, 1:35am UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/8 "2010-03-12T01:35:55Z")
The codes cannot tell you that an O2 sensor needs to be replaced. What were the actual codes? Here’s a good guess b/cit happens a lot. You are going to spend the $$ to buy the sensors. You’re then going to go thru hell replacing them possibly including more $$ for the special socket. You’ll finally finish and sigh in satisfaction only to find the engine light still on with the same codes. Look, I’m not saying that is what will happen. But it happens - A LOT - watch this board for a few days and you’ll see it. “The code said the X was bad so I replaced it, but the code is still there. So I replaced it 3 times and the code is still there…” ---
**Author:** ![recoiled](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@recoiled](https://community.cartalk.com/u/recoiled)\ **Post date:** [March 12, 2010, 2:23am UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/9 "2010-03-12T02:23:17Z")
P0138 02-B1-S2 P1687 Those are the codes written down. ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [March 12, 2010, 2:32am UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/10 "2010-03-12T02:32:42Z")
Well, I have no idea where anyone would get the notion to replace 2 O2 sensors from that - one at most. P1687 has not a single thing to do with an O2 sensor. It has to do with your instrument cluster losing contact with the PCM. This is likely a wiring problem or a bad cluster. P0138 refers to the circuit for the rear (after the cat) sensor on bank 1 (whichever cylinder side has cylinder 1 on it). This could be a bad sensor but could also just as easily be a wiring fault. You might say screw it & just replace the sensor and that may work. Otherwise you need a repair manual ($20) and a multimeter - which you might want to have to check out the cluster code anyway. ---
**Author:** ![recoiled](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@recoiled](https://community.cartalk.com/u/recoiled)\ **Post date:** [March 12, 2010, 3:03am UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/11 "2010-03-12T03:03:29Z")
thank you again ---
**Author:** ![geeaea](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@geeaea](https://community.cartalk.com/u/geeaea)\ **Post date:** [March 12, 2010, 7:39am UTC](https://community.cartalk.com/t/99-jeep-cherokee-sport/45919/12 "2010-03-12T07:39:57Z")
To test the wiring, I’d reset the PCM (unhook the battery) and just unhook the rear O2. If you’re still seeing the code (P0138 shows it being out of plausible range for too long), then the wiring is shorted. It may throw another code too. Otherwise it should be the sensor …and that you can lay on the ground to do it. You don’t even have a skid plate in the way of you reaching around here and there. Piece of cake.