cbridges

I have a 2000 TL with 113K miles.

I recently had an oil leak, not sure when it started, but there was burned oil all over the front valve cover, and kinda all over the engine. The oil was never low, according to the dipstick. The only symptom was that I could smell oil burning. Since the burned oil was on the top of the engine, I figured I'd start with the VC gaskets (oil leak goes from the top down), so I had the VC gaskets replaced.

A couple of weeks later (I don't drive it much), the CEL came on (the TCS light might have come on at first, but it's not on now, just the CEL). Ran an OBD scan and it say P0131 (O2 Sensor Low Voltage, Bank 1 Sensor 1). So I'm considering changing the O2 sensors, or at least the upstream sensor.

I watched some videos on how to do it, and started to look under the hood to locate the upstream O2 sensor cable from the top. I'm assuming this is the one....


Upstream O2 sensor cable from the top, lots of grime on it.

It could just be that some oil got in there. It's pretty oily. It just seems pretty coincidental that the O2 sensor would just go bad. But i supposed it could happen.

I tried to squeeze it, but it didn't seem to release. Not sure if I'm supposed to squeeze that clip at the top. It seems it might not release too easily because of the caked on grunge (burnt oil?). Maybe I need to blow with compressed air? Everyone seems to say release it from the top, rather than try to do it from the bottom.

But I also noticed a couple of cables that aren't plugged into anything, and I have no idea what they are. Does anyone know? (Sorry if this seems like a dumb question. I figure I'd be having a lot more problems if there were 2 connectors unplugged that should be plugged somewhere. But I don't see anywhere that they would go.)


You can see the 2 cables, not plugged into anything, right in the middle.


This one looks kind of like an O2 sensor cable, but it doesn't seem to have any metal connectors, almost like it's terminated. It comes out from around the rear VC.


This one almost looks terminated as well. Comes from the right, near the intake hose.

Any thoughts on those hoses? And suggestions regarding the O2 sensors?

Thanks in advance.

Saudade

I responded to this in my own thread on this issue but I'll add:

I'm not sure that's the right one based on your picture but it looks familiar. I got underneath to follow the harness to find the connector. When you press the tab, you pull up on the connector half. I could not reach in from above to grab it.

The connector attached to the sensor also mounts to the bracket. I had to unbolt the bracket in order to get some slack and be able to maneuver the connector to separate them. Mine too was so full of grit, dirt, oil, etc., I used a pick and some brake cleaner to flush out under the tab.

I'm not sure what those other connectors are for. Since they're capped off, I'll assume they are for options your TL doesn't have. I've not noticed any capped connectors on mine in that area. One of the experts will be along soon.

whitetiger5

Hi, it's not easy to do (because it requires some special tools) but did you check the fuel pressure before concluding that the issue is a faulty O2 sensor?

I've seen others skip over that part and ending up replacing a perfectly good O2 sensor only for the problem remain.

The service manual walks you though that diagnostic process...

The grimy connecter isn't too much of a problem (because it more than likely untouched) and i don't recall touching anything in that area when I did my valve cover gaskets.

cbridges

@whitetiger5 I'll have to check that out. Thanks.

In the meantime, I pulled the cables apart, and there was definitely oil inside. They weren't swimming in oil, but there was some oil. I wiped them off, blew some air into the top one (car side) and wiped off, and dipped a Q-tip into the bottom one to soak up any oil that I could. Plugged it back together, and drove some, but it didn't clear the code. I tried clearing the code manually from my OBD tool, but the TCS light stayed on, then when I drove a little, the CEL came back on as well.

I also tried doing a live monitor, but the O2 Bank 1 Sensor 1 didn't show much voltage. I'll need to follow the steps from the manual though..

BTW, here's a screenshot fo the live monitor.



And here's the proper troubleshooting guide from the service manual, if anyone's interested.

cbridges

So, I started to do the tests above. But when it gets to the "until the radiator fan comes on", I have a problem. My radiator fan never comes on, even when the coolant temp gets to 217 it never kicked on.

I finally checked the relays, and they seem fine. Switched them between the condenser fan and the coolant fan, and the condenser fan always comes on, but the coolant fan doesn't. Then I ran direct power from the battery to the radiator fan with test leads, and it doesn't come on. I'm not sure if this is at all related to the O2 sensor code, but this is another thing I'll need to get fixed (or fix myself). Will probably fix this first and see what happens.

What's the point of "until the radiator fan comes on"? Just to make sure that the engine is warmed up?

BTW, according to the temp gauge inside, the temperature never even gets to halfway. Of course, I'm not driving it long distances.

cbridges

Just ordered this cooling fan assembly. Looks like I should be able to slide the old one out, and slide this one in, without having to mess with the radiator (much). The original is a Denso, but this one is compatible and has good reviews.

whitetiger5

Yes, to make sure that the engine is at operating termp, and that the coolant in the system is at least at the operating temp as well so that cold coolant doesn't come through and bring the engines temp below the ideal operating range.

i'm fairly confident that if you: leave your OBD scanner connected and record your O2 data while driving around as they direct you to (at least 3000 rpm, and some load) and can confirm that the O2 voltage stays below that value it's time to look at your fuel pressure.

the O2 data in your existing screen shot supports this.

cbridges

Ended up taking to a shop to get their opinion. I didn't have tools to test the fuel pressure, and wasn't exactly comfortable doing that.

I assume they tested according to the manual (including fuel pressure if needed), because they had suggested the steps in the manual to me in an earlier email exchange. They ended up suggesting replacing the upstream O2 sensor. Quoted $249 for parts and installation. I told them I'd just do it myself. They didn't charge for any diagnosis.

But, interestingly, when I picked up my car, the CEL and TCS light were both OFF. They didn't come on while I was driving home. Nor did they come on when I drove anywhere else. Usually, they had been coming on rather quickly after resetting the PCM. Not sure what they did to make that happen.

Got the parts from Amazon for $50 (upstream) and $28 (downstream), and another $21 for a removal tool. So about $99 total + tax.

Me and a friend ended up replacing both. Took about 2 hours. No codes since. Seems to ride smooth.

Also got a new cooling fan from Amazon ($60) and that took about 20 minutes to replace.

So all is good for now, I think.

Thanks to everyone for the help.