H3What

I recently purchased a new 2008 JK Rubicon (2 door) and about 3 weeks ago my check engine light came on. It stayed on for a few days then went off. It has done this 3 different times so I finally took it to the dealer. They have had the jeep a few days now and all they can tell me is that 3 of the 4 O2 sensors are throwing a ground fault code and that they don't know where the ground is for the O2 sensors. They even said that Chrystler hasn't been able to give them any direction on where the common ground is for the sensors. Seems a little odd to me, but I'm new to the jeep community so who knows.

Has anyone else seen this problem? Maybe someone on here has had it fixed and can tell me what to tell the guys at the service department to do to fix the problem. I appreciat any help you guys can offer!!!

Ted_Grevers

Has your Jeep gone swimming since you purchased it? Did you hit something on the highway that might have damaged a harness? I'm guessing that you have a harness that's rubbing on something that's causing the ground fault, or you have a bad ground to the chassis somewhere.

-t

07JKX

check your front drive shaft towards the front of the vehicle... had this happen to a friend. If the cable is grounding... there will be a noticeable ring around your driveshaft and you should see the wire hanging down. Mine were zip tied up there from the factory.

husker_shoe

according to this schematic, the ground for all 4 of your O2 sensors heater circuit is G104, however if I try to find a location for the ground, it tells me it's in the engine harness, but will not show a picture of the ground itself. If you look at the picture of the engine bay, it shows you a G103 and a G105. It should be in the same area as these two. They code the grounds based on location. For instance a G100-G199 would be in the engine bay usually, a G200-G299 would usually be between the A pillar and B pillar, so on and so on. Anyhow, they or you need to check the integrity of this ground circuit between at least one of your O2 sensors and G104. Preferably from every sensor. Check the harness routing and make sure it's not pinched or rubbing anywhere. Everything depends on what the actual DTC is however

insanegecko

um...dont want to sound like a jerk, but im a mechanic, what do you need to know? location of g104?

the schematic of oxygen sensors you have is kinda vague, technically the O2 sensors ground is the ecm, what p code do you have? is it the heater circut or the data stream?

Gex

by the way the source of the problem is most likely the sensor that they dont have a code for. In your diagram the ecm IS ground for the heater circut.... it works like this:
on cold start oxygen sensors dont really start to oscillate until they are hot, in the 80s the heat of the exhaust warmed them up, this is why obd1 computers dont accept data from o2s until five mi after startup. Now with 4 wire sensors you have 2 wires dedicated to the heater circut, 2 to the signal. Key on engine off you should have 12 volts on the pin at the sensor wires coming from ecm, to turn the heater on the computer then grounds the heater internally....keep in mind almost every computer/ emission circut is ground side controlled (ie purge valves, ldp, o2 heater, sai pumps, egr solenoids etc). More than likey the computer is seeing to high and amperage flow on the heater positive if the code is heater related...this is interpreted as a short to ground...keep in mind this will fry an ecm eventually... if the short is on the signal supply or return it would probably throw a code for staying lean....the heater code is p0153 i think for b1s1..
to diagnose: disconnect all ecm plugs, and all 02 sensors, use a digial multimeter set on ohms/resistance. connect ground side to either chasis or neg bat cable. probe each wire to the o2 sensors (4 sensors x 4wires= 16 ) if any of those have continuity to ground with ecm disconected theres you problem wire. This should take all of 10 min with a decent Snapon scan tool even less with DRBIII with every dealer has, you might want to find a new dealership as well


let me know what the codes are if you can, hope this helps

husker_shoe

That's what I was unsure of...if it was a DTC for the heater or the sensor itself. I'm a GM tech and I dont have access to Jeep service schematics, but I do have access to Alldata(or as I like to call it, "Somedata"). Best I could do with the schematics w/o calling a buddy at the Jeep dealer. Seems the problem is usually the Jeep dealer though. Man, if I diagnosed cars like some of these stories I've been hearing, I wouldn't have lasted a month for GM. Some dude earlier was saying he had a coolant leak from a freeze plug under warranty and the dealer would cover the freeze plug and labor, but not the coolant. You have got to be kidding me right?!?!?!

H3What

insanegecko -

I picked the jeep up yesterday from the dealer. Here are the codes: P0032 - O2 Sensor 1/1 heater circuit high, P0038 - O2 sensor 1/2 heater circuit high, P0052 2/1 heater circuit high, P0058 O2 sensor 2/2 heater circuit high. The tech at the dealer didn't know what to do, but they told me that Chrystler said it was probably the Power Control Module so they are going to try and replace that next week! What would your advice be on these codes. Also, the light doesn't stay on. About two hours after I picked it up, the light went off and stayed for a day and then came on again today at lunch. Thanks for the help guys!!!


Give me an old jeep or an old bronco and I'm fine...I don't like all this computer controlled stuff!!!!!

insanegecko

also keep in mind the codes are two trip failure codes, which is probably why is comes on a few days after the dealer clears it.

id be surprised if the ecm is at fault, if they wind up putting a new (reman) one in it probably will be worse than the original

tdshepard

I had same codes and intermittant failures. Dealer replaced the PCM and so far all has been fine.

H3What

Well, they are replacing the PCM next week so hopefully that will fix the problem. Thanks for all your help!