2006 NA Baja with 145k on the odometer started throwing P0030 OBDII errors, indicating issues with the upstream O2 sensor. Going to work on this myself so I'm trying to source tips from anyone that has already worked on it.
The location? Without having gone looking for it yet I think it is on passenger side of the engine compartment, maybe accessible through the wheel well if the wheel is removed?
Before replacing it outright (with my mileage I assume it is probably just time, but still...) I'd like to test the original to make sure it isn't something simple like a bad connection in the harness. I understand that with ignition on, engine not running and I assume cold I should find 12v on one of the lines to the sensor. I understand I also should be able to confirm a specific resistance across a pair of wires on the sensor, that being for the heating element. Anyone know the specific tests?
I've read to start soaking the sensor area with penetrant at least a day prior to attempted removal. Anyone had any issues getting it out? As mentioned, it has been in there for 145k miles which is in a 4-season environment of SE PA.
From lr60's thread if replacement is needed I was going to go with the Bosch 15501 to save a few bucks over OEM. Probably from Rockauto, Amazon or eBay. (Tempted to open one of the Amazon credit card accounts to get $70 off the part.) Anyone have concerns of the Bosch product vs OEM?
Is an O2 tool such as Harbor Freight's crow foot tool necessary on our Bajas or will I be able to get to the sensor with an open ended wrench?
Thanks in advance!
O2 sensor testing/replacement tips requested
Moderator: bajabob
Re: O2 sensor testing/replacement tips requested
Ok, so I got into it today.
The harness plug is accessible on the passenger side of the engine along a strip of 3 or 4 plugs total. I removed the air intake snorkel between the filter box and the scroop above the front grille to make this easier to access. I couldn't get my test probes into the harness side plug without bending the bracket a bit.
I haven't been able to find solid confirmation of the 4-pin sensor pinout. With my multimeter set to 20v, the sensor disconnected and the ignition set to on but the engine not running I started testing for voltage between the harness side pins and ground. Looking at the plug while still on the bracket from the passenger side of the car I think it was the upper inside pin that I found to be carrying 12v. This was once the engine had cooled a good bit, I think when I first tested this pin I didn't see that reading. I think the inside lower pin was 0v which I would then suspect these two pins make up the O2 heater power and return. On the O2 side plug these wires were both black and it would make sense that for a heating element wires could be the same color as polarity wouldn't matter. The other 2 pins read somewhere in the 2-3v range. I don't recall their colors on the O2 sensor side but I think one was white and the other blue with white. I didn't test any continuity to ground or resistance on/between any of the wires as I didn't want to send back any voltage and risk making matters worse. Again, these wire arrangements are just my suspicion. If anyone can either confirm or improve on these details it would be appreciated. Even without knowing the true pinouts or testing procedures, with the measurements I got I feel confident that the harness side is looking good and I'm going to proceed with sensor replacement.
The mounted sensor is visible down through the engine compartment but you're going to want to access it either from the passenger wheel well or from underneath. It is located on the front of the catalytic converter right under the passenger wheel transmission CV joint if I recall correctly. If you're going to access through the wheel well you'll probably want to pull the rim and cut the wheels to the left. Since I already had the Baja up on the jack I accessed from underneath and used the previously linked HF crow-foot O2 socket. I don't know that any of the more normal looking tall sockets that simply allow the wire to bend to the side through a slot would be able to fit in there and I really don't think you could get this without a similar specialized tool. I had hit the sensor with some WD-40 about 10-15 minutes earlier, didn't have my PB Blaster handy. It took a good bit of force but I did crack the threads about 1/8th of a turn, enough to know that I'll be able to get the sensor out once I have the replacement available. Happy with this knowing how long that has been exposed.
On to obtaining a replacement!
The harness plug is accessible on the passenger side of the engine along a strip of 3 or 4 plugs total. I removed the air intake snorkel between the filter box and the scroop above the front grille to make this easier to access. I couldn't get my test probes into the harness side plug without bending the bracket a bit.
I haven't been able to find solid confirmation of the 4-pin sensor pinout. With my multimeter set to 20v, the sensor disconnected and the ignition set to on but the engine not running I started testing for voltage between the harness side pins and ground. Looking at the plug while still on the bracket from the passenger side of the car I think it was the upper inside pin that I found to be carrying 12v. This was once the engine had cooled a good bit, I think when I first tested this pin I didn't see that reading. I think the inside lower pin was 0v which I would then suspect these two pins make up the O2 heater power and return. On the O2 side plug these wires were both black and it would make sense that for a heating element wires could be the same color as polarity wouldn't matter. The other 2 pins read somewhere in the 2-3v range. I don't recall their colors on the O2 sensor side but I think one was white and the other blue with white. I didn't test any continuity to ground or resistance on/between any of the wires as I didn't want to send back any voltage and risk making matters worse. Again, these wire arrangements are just my suspicion. If anyone can either confirm or improve on these details it would be appreciated. Even without knowing the true pinouts or testing procedures, with the measurements I got I feel confident that the harness side is looking good and I'm going to proceed with sensor replacement.
The mounted sensor is visible down through the engine compartment but you're going to want to access it either from the passenger wheel well or from underneath. It is located on the front of the catalytic converter right under the passenger wheel transmission CV joint if I recall correctly. If you're going to access through the wheel well you'll probably want to pull the rim and cut the wheels to the left. Since I already had the Baja up on the jack I accessed from underneath and used the previously linked HF crow-foot O2 socket. I don't know that any of the more normal looking tall sockets that simply allow the wire to bend to the side through a slot would be able to fit in there and I really don't think you could get this without a similar specialized tool. I had hit the sensor with some WD-40 about 10-15 minutes earlier, didn't have my PB Blaster handy. It took a good bit of force but I did crack the threads about 1/8th of a turn, enough to know that I'll be able to get the sensor out once I have the replacement available. Happy with this knowing how long that has been exposed.
On to obtaining a replacement!
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Acro2pilot
- Scoobytruck Master
- Posts: 227
- Joined: Fri Sep 07, 2012 5:39 am
Re: O2 sensor testing/replacement tips requested
They fail, no biggie. Amazon usually has a good price and if your a prime member you get it fast for free.