VerbalKent

iTrader: (1)

Hi everyone!

I just had my 90K service completed on my 2001 LS430 as well as the upstream O2 sensors replaced. The car was due for the 90K, and the sensors were done because of a PO135 on bank one, sensor one. Since they were original units, I had the passenger side done as well figuring that it too was probably on its way out...which may be the problem as I might have 'fixed' something that wasn't broken? Anyway, all parts were OEM, and all was well until I got a CEL for a PO125 (Insufficient temp. for closed loop fuel control) a couple of days after I got the car back. A little research shows that while it could be 'coolant stuff' related, it may also be O2 sensors again. I'd rather check all of the 'easy' stuff before taking it back, like the condition of the temp. sensor and coolant level, but I was wondering if anyone else experienced this and could shed some light. Thanks for reading, and thanks in advance for any help that you may offer.

xtr3me

Been there before....
Check coolant for proper level first, my past experience with this fault was a bad thermostat

VerbalKent

iTrader: (1)

Thanks Xtr3me! I'm hoping it's something simple like that...I supplied the parts, so if it is the thermostat, I'm gonna have to eat that labor to replace it

xtr3me

I stand corrected..
Hopefully just a faulty 02 connection... It's definitely an upstream fault if it's an 02 sensor. I should add the P0125 DTC was on a Mustang and the thermostat was trash.
Evidently our Lexus fault codes are different. I thought all DTC were the same, but after looking at the LS OBDII DTC's nothing in the coolant arena is related...

VerbalKent

iTrader: (1)

Hmmm...so it's possible that one of the O2 connectors may not be seated properly, or that I just may have a bad Denso on one or both sides? Thanks for the follow up Xtr3me...I checked the overflow and it was sitting just over the 'L', so I topped that off...radiator looked fine, so time permitting, I'll be crawling under the car to take a look at the sensors...if I don't get around to it, I'll just go back to the shop Monday and ask them to take a look...again, thanks Xtr3me!

VerbalKent

iTrader: (1)

Just following up on this...I finally had time (and cooperative weather) to get underneath the car and take a look. After replacing the coolant temp. sensor ( the one near the T-stat housing) and still getting the code, I used the info the Xtr3me sent regarding the O2 sensors and the possibility of a short or shorts. What I found was what looked like an exposed frayed wire in the O2 sensor harness that had been previously factory taped (?) coming from the car on the passenger side...I should've taken pics, my apologies...but if you have this 'condition' on your vehicle, you'll have no problem seeing it...it just looks..well...wrong. Anyway, I broke out the soldering iron to start repairing it and realized that after cleaning it a bit (more on the cleaning in a sec), it wasn't two broken wires twisted together as I first thought, rather it was was still 'connected', but it was a larger gauge coming from the car than what was at the actual plug before going to the 'harness plug side'...again...if you have this condition, it will make perfect sense when you are looking at it. I cleaned up the oil that was on the harness and thought 'why is there oil on the harness?'...and figured out that the valve cover gasket has a small leak. Never knew because it hits the plastic pan so there's no spot on the ground, and it's not hitting the manifold, so no smoke...what it was doing was dripping on to that exposed wire I mentioned earlier. I resealed the wire, replaced the VC gasket, and it seemingly has done the trick...I know this may have seemed like a long write-up (because it is LOL), but sometimes we have issues with our vehicles that kinda warrant them...this was actually a combination of two issues that since, a recent T/B service was performed along with two new O2 sensors, may have been thought to be related, when it actually appears to have been the wire and the gasket all along...well, for the PO125 anyway...hope this helps someone, even though reading it may have been LOL

BradTank

Thanks for following up with the solution, always appreciated.

The fact that the wire was "taped" almost leads me to believe the shop that recently replaced your 02 sensors used "universal" ones and just did a poor job splicing them in as opposed to using ones that were "plug and play" into the factory harness. Maybe they clipped them in the wrong spot and actually went into the harness? I don't think any part of the factory harness would come with electrical tape on it to join two different wires.

Do you think that's what could have happened? If so, I really think the shop responsible are some real hacks.

VerbalKent

iTrader: (1)

Thanks BradTank! As much as I initially wanted to think the shop may have been at fault, I wanted to be sure before I went back and made a fool of myself This is why I went back under the car to take a look. Truth be told, if my 'real car' (71 Impala that I'm putting the finishing touches on a big block rebuild) weren't hogging up the garage, I would have done it all myself, but doing any of this in the weather we were having was just out of the question LOL.The O2's are OEM Denso's, so they didn't need to fab the harness...in fact, it was the 'vehicle side' of the harness that was in question. It was in the factory split loom and the wire (white one if it helps for reference?) seemed to have been previously taped and re-inserted back in the loom...I bought the car used so, it could have very well been the previous owner that did it or had it done...the tape was brittle which to me implied it had been on the wire much longer than the 4 or 5 days or so since I got the car back. I think it was the combination of the VC gasket leak and that wire exposure that threw the P0125... a 'short or open circuit' is a possible cause for the code, which fit my scenario perfectly. Funny thing is, it may have never thrown the code if I never replaced the 02 sensor as that harness would have not been 'disturbed' Anywhooo, I'm glad I looked under there, because I would have gone back there and blamed them for something that they didn't do...they have a really good rep and as far as I can see, well deserved...I agree that there are some really bad shops out there, and when some of them see our cars, they just start counting money, but thankfully, these guys aren't like that. Again...thanks for the inquiry, and my apologies for the long reply...I just like to try and be as thorough as possible