P0135 Code on 2003 Olds Aurora 4.0 V8

I think a Bosch 02 in any domestic car should be on that list unless it was a bosch sensor that was used when it rolled off the line and it wasn't in yours! the best way to prevent issues like this is to always source it from the dealer!

My mechanic replaced the Bank 2 upstream O2 sensor with another Bosch unit, so now both upstream sensors are new and both are from Bosch and the problem is completely gone. I'd recommend that everyone replace both of their upstream O2 sensors if one goes bad and they should be of the same brand because the PCM compares the output of each to decide whether to throw a code or not. My original Bank 2 sensor actually was still good but the 2nd problem arose after changing the Bank 1 sensor. This made the two upstream sensors so far apart in terms of behavior that the PCM began throwing the O2 heater circuit code for the Bank 2 sensor. Always replace O2 sensors in pairs!

So Bosch 02's are a savings because u have to replace them in pairs? because the pcm continues to code because it's comparing the new bosch unit against the original still working sensor and thus the original sensor is defective as well? The best route is to replace the Correct brand of sensor upon replacement and on a v engine using the same sensor as factory would have saved u the labour and cost of two sensors! Now Im not saying that 02's should be left in till they code because alot of them do degrade and never code and changing an 02 out with a correct new part will almost always net a mileage increase. But advising to replace two when 1 correct sensor would suffice in order for the cheaper part to maybe not code is poor practice and advice in my opinion!

...I have a feeling he'll be back...

I agree with your assessment that I should have purchased a single Delco O2 sensor to start out with. I wish I'd had. They are a little harder to find these days (all of the big parts chains are pushing the Bosch O2 sensors heavily). I brought my mechanic the first and second Bosch units, so it was definitely my fault. He probably would have ordered the original sensor from a GM dealer. I was looking to save a few bucks and didn't know any better at the time. I've got a couple of 1990's Fords as well (Crown Victoria and Aerostar), so I'm wondering if the same is true for them. When an O2 sensor goes bad in one of those, should I only get the Motocraft replacement unit?

yup!

On a non heated 02 it isn't as critical because the difference in heater element resistances from brand to brand and thus the required shift in duty cycling to keep them at operating temperature is where repeat occurences of codes occur and why! I just tend to defer to the dealer parts dept for all of the engine management sensors as they vey rarely sell me one that isn't long enough or doesn't plug in correctly the first time! Add issues like fuel air ratio sensors that appear and plug in like 02's sensors on the same product line and you can run into some real headaches when somebody installs a cheaper 02 in where a wideband is supposed to go! the location of the 02 sensor in relation to the catalyst also has an effect and is one more reason aftermarket weld in "universal" converters cause headscratching results at times! My suggestion is to let your technician source the replacement parts for you in future! we never install customer supplied parts at my shop as it leads to headaches just like this! We also never use Bosch 02's either though! It's not a bias it's a proven scenario time and time again that the bosch will turn the light back on in 90% of the applications we work with! Your attempt at saving money by bringing him a substandard part cost you more money by having to remove a perfectly good working sensor and install a substandard new and pay for additional time and labour! your mechanics error was in not knowing any better!

Jeff, thanks for your advice on this topic. We're all better educated now. Are there any aftermarket O2 senor brands which are acceptable on GM and Ford applications? Denso?

If you can see the manufacturers stamp or markings on the sensor that's removed then that's the one to source it through. As an example most Dodges for the lonest time were NTK and if your purchased an NTK from the aftermarket as long as the parts man had a proper cross reference and book and used it u got a sensor that worked as good as oe. Problem still with this is finding a parts store that carries all the correct brands because there's no money to be made in having tons of inventory tied up when they can stock lower grade "universal" junk that works like crap in 99% of the vehicles. The other thing to always remember is any changes made to the parts to make them last longer etc by the manufacurer will be sold at the dealer parts dept. Example if the oe discovers through testing that a hotter or colder spark plug works better then the heatrange used from oe it'll be put into the system as the new correct application which when you go to the dealer parts dept is what u will get. If you just went down to the zone to buy your plugs by application you may never be aware that there was an improvement made and you just wind up with the same old fouling heatrange plug. And that's the best scenario if u stick with the same manufacturer ie putting a champion back where a champion came out and not jamming a pos Bosch platinum in there bcause the kid on the counter tells you they are the best plugs out there! Im not agains aftermarket parts! They're the brands that are installed from factory, my beef is somebody trying to sell you something because it's cheaper and telling you it's the same thing when it isn't and won't work the way the factory parts did and would! Now I have to ask why u don't u want to buy parts from your local dealers?

Thanks Jeff. To answer your question, I've often been surprised by the prices on some parts from the GM dealerships. I did just have two new crankshaft position sensors also installed (GM TSB for 2003 Aurora's) and went with the original Delco parts. The price wasn't too much higher than aftermarket (aprox. $89 vs. $61), so I went with original. For the O2 sensors, the Bosch units were aprox. $43 each vs. aprox. $125+ for the dealership O2 units. On some parts, the difference between original and aftermarket is small and on others, it is much more. Besides Bosch, do the other aftermarket parts manufacturers/distributors supply parts that give you as much trouble? Also, I'm told that Bosch supplies some very good OEM parts for German cars (Volkswager, Mercedes, etc.). Do those parts get manufactured to better quality standards than those that they supply to national chains such as the Zone?

Firstly Bosch isn't the only offender they just seem to be the most common on here as they seem to sell alot of 02's and spark plugs, both of which in my opinion work poorly in just about every instance I've seen them used! Just last week we had another brand with the word streak in it's name that had a 1 month old ignition rotor fail in a 95 camry 4 cylinder! The thing is when you put a part in for a no start and it starts working right away then you know it was diagnosed properly likely and you can go on to the next challenge! A month later you may have a po'd customer and pull some hair out but when the testing leads u again down the same road and u learn your lesson and your parts supplier covers the cost and u at least know how to diagnose it! When u put in an 02 sensor that won't stop coding because the heater element is incompatible with the pcms' logic program and the diyer has no clue how the circuit in the pcm works and assumes they did something wrong or worse yet throw a pcm in the car because it's the next step in the troubleshooting chart and the bosch is new and new means good right then yeah I think selling those types of parts and telling customers it's a universal application and will work should be illegal! I've been bit by ignition coils that go from not sparking at all to only sparking on warm days after 1 month of use and I've had crank sensors right out of the box that wouldn't register! I've had alternators that didn't last a year and wiper motors that wouldn't park right out of the box! In defence alot of aftermarket parts are fine! I've even used Bosch's reman line of starters and alternators and had no more issues then others! Again my beef is with the lowest of the low junk that gets pushed at stores like the zone that cater to the diy market! there's a reason alot of shops don't use stores like the zone and pepboys and it's not because of pricing! It's because alot of there lines won't satisfy most customers expectations! Alot of diyers will tolerate squeaky brakes and cel's that stay illuminated because of the savings but my customers want better then oe quality on there parts and service above and beyond what they can get at the dealer! the only way I can supply them with that is using what I know is the best parts for there application! I suppose if Bosch is OE on a BMW it may work but I'd still trust the BMW dealer to get me the correct part Bosch or whoever. I understand your skepticism on the 02 sensor scenario at the dealer but you have to remember you only had 1 option there as the bosch isn't a working part so therefore it isn't an option! In a nuthsell I like Wells and Echlin ignition parts, and some Wells engine sensors plus there website is top notch, I like Goodyear belts and hoses and Monroe Struts and Wagner and Raybestos brake parts. My shop's main parts supplier is an A/C Delco distributor that is not affiliated with the dealer so we can get parts through them sometimes faster and cheaper then the dealer and the part numbers are the same which makes it easier!

Ya wouldnt want to hand out that distributor info would ya jeff ? I too despise the zone products due to my own horror stories and experiences but seems to be all that around my area other than the one market enterpriseing dealership that we have in this one horse town of mine.

My local distributor is an independent jobber that's affiliated with AC Delco so Im not sure you save anything by having him ship stuff stateside to u. Rockauto.com also sells alot of A/C delco!