Jim,
I used his cars information when I punched it into mt DTC look up software.

Hi,

OK, my misunderstanding. But, your code description is still in keeping with bad O² sensors. If the signal from the sensor is non-existent, then a code speaking directly to the sensor will be thrown.

But, if the sensor is sending signals which are outside what the DME has been programmed to expect, it gets confused. It doesn't fault the O² sensor because it is getting a signal from it. But, it can't find any Maps to use which correspond to the signal values from the sensor, so it will code that the DME (Mfr. AF Metering) cannot function properly because that's all it knows, it doesn't know the O² is bad since it is getting an actual signal from it. An O² sensor can fail outright or it can fail progressively, sending signal values (voltages) which the DME has not been programmed to identify or interpret.

In this specific case, it could actually be one bad O² sensor, or any/all of them, which is one reason you want to change them all at the same time. They're not like lightbulbs, where you simply replace the burnt out one. Instead, they are all linked as a part of a system. Unfortunately for the wallet, this system is only as good as it's weakest link. But that doesn't mean the the remaining sensors are operating properly. Zirconia sensors work by exposing a certain surface area to Oxygen in the exhaust stream. Over 30k mi., this surface area is reduced as carbon and other contaminates condense from the exhaust stream and onto the Zirconia surface, meaning that Oxygen is now denied to that surface area, and the voltage(s) which the sensors produce decline with time as well. It is the value of these voltages which the DME uses in determining the optimal AF metering for the conditions the sensors are telling it are present.

These kind of codes are the ones which require that you put on your detective's hat to figure out what it is exactly which is causing the AF Metering to function improperly. A bad MAF can also throw similar codes as well in addition to throwing a bad MAF code. Hope this helps...

Happy Motoring!... Jim'99

Everyone should listen to Jim on this one...I've been there done that! Once one goes they will all start setting codes and if you replace them one at a time you'll spend more time in the dealership than any of us would like to. Luckily my extended warranty covered them...but only as they expired...so I ended up dropping my car off at the dealership once a week for a month! PITA!! :cheers:

Well, for the record I dont believe anyone disagreed with Jim. We know hes a knowlegable guy.

I've been reading this thread with interest.
I'm at 47,500 mi on my non-S 2001, purchased about 1.5 years ago when it was at about 30 to 35,000. I can say that my car runs as fine as I remembered it at the time, but then again, there might have been a gradual deterioation since then.

My question is how do I know they need replacing? There are no cel lights yet and the car is feeling fine. As per MNBoxster, I should be way over the 30,000 mi sensor life limit.

Also, how good are the discounted ones? The Speedy/PartsTrain guys are selling them at approx $35 each. The OxygenSensors.com guys are at $114 and even then are considerably cheaper than Porsche. Is this case an exception to the rule of you-get-what-you-pay-for?

Having just experienced a Mass Air Flow sensor failure at a bad time, I'm contemplating the replacement of my O2 sensors before they have a chance to fail. (I generally like to choose the place and time of my disasters.)

I'd just go ahead an do it if it weren't for the expense of the OEM sensors. I'll keep an eye on this thread for the next few months. I hope Jim keeps us updated on how well this is working.

Ok, I finally got around to replacing all 4 sensors and I keep getting the following codes (I reset it twice and they come back within 5 miles):

• P0131: Oxygen Sensor Ahead of Catalytic Converter (Cylinders 1 - 3) - Signal Wire Short Circuit to Ground or Incorrect
• P0137: Oxygen Sensor After Catalytic Converter (Cylinders 1 - 3) - Signal Wire Short Circuit to Ground or Incorrect
• P0151: Oxygen Sensor Ahead of Catalytic Converter (Cylinders 4 - 6) - Signal Wire Short Circuit to Ground or Incorrect
• P0157: Oxygen Sensor After Catalytic Converter (Cylinders 4 - 6) - Signal Wire Short Circuit to Ground or Incorrect
• P1115: Oxygen Sensor Heating 1 After Catalytic Converter - Above Upper Limit
• P1119: Oxygen Sensor Heating 2 Ahead of Catalytic Converter - Below Lower Limit

I followed the instructions exactly and all the colors matched up fine. Anyone else have issues?

oh yeah, I used USOS-4000 from Parts Train (the link above) and I have a '99

I know this is going to add insult to injury, but quite often a bad or failing MAF will cause the computer to give O2 sensor fault codes. They have quite a lot to do with one another and play off one another frequently.

If you are sure your sensors are clean (no greasy fingers on the tips before the install) and the wiring is correct, it just might be your MAF. I hope it's not but it just might be.

I currently have no O2 Sensor error code on my boxster right now but i was wondering, IF i were to clean them anyway, Would that improve my performance?

If so, how should i clean them?

The problem with attempting to clean oxygen sensors is that they get a carbon buildup and they're "burned" a little or a lot. There's hardly any way to clean them without scratching the carbon off and then you will damage the sensitive coating on the sensor itself.

I think they're replace only. The MAF is really the same way, but since it's not on the exhaust side it doesn't have carbon buildup and cleaning it can work some times.

I see, thanks randell.

Generic O2 Update
 

It's been about 4K miles now and she still runs beautifully with the generic sensors. Readings are still nice and within range. :dance:

This exact thing happened to me last night. All colors matched and accounted for, and I got most of the same codes (plus a few new ones). The codes and the descriptions are compliments of Durametric... That is one cool toy :)

Stats: USOS 4000 sensors from Speed Auto (Listed on the previous page). This is a 97 Box with the Motronic 5.2.2 DME. All 4 sensors were replaced.

• P0131:Factory Fault Code 10 - Oxygen sensor ahead of catalytic converter (cylinders 1-3)
  Short circuit of wires or limited voltage increase
  
• P0151:Factory Fault Code 18 - Oxygen sensor ahead of catalytic converter (cylinders 4-6)
  Short circuit to ground at signal wire of incorrect voltage
  
• P1119:Factory Fault Code 5 - Oxygen sensor heating 2 ahead of catalytic converter
  Below lower threshold
  
• P0137:Factory Fault Code 12 - Oxygen sensor ahead of catalytic converter (cylinders 1-3)
  Short circuit
  
• P0157:Factory Fault Code 20 - Oxygen sensor behind catalytic converter (cylinders 4-6)
  Short circuit to ground at signal wire or incorrect voltage
  
• P1117:Factory Fault Code 14 - Oxygen sensor heating 1 ahead of catalytic converter
  Below lower threshold
  
• P1121:Factory Fault Code 4 - Oxygen sensor heating 2 ahead of catalytic converter
  Below lower threshold

If anyone else has ran into this, and knows what was done to fix it, please let me know. I'm sending a message to BinaryC to see what his resolution was. I'm going to have just a few minutes tonight to look at it, but as soon as I resolve it, I'll post the answer to this thread.

Thank you guys!

Cheers!

~Aaron

I would check to make sure all of your connections are tight and that no wires have been swapped anywhere. It's usually a really good idea to solder these connections, as the signal output from the sensor is barely 1 volt (at maximum) and any resistance at all will hide the true value. Eve if you're only soldering one wire per sensor, make it the black one.

If you have a multimeter, set it to DC volts. With the engine fully warmed up, disconnect the O2 sensor prior to the first cat (nearest the engine), put one lead on the black wire coming out of the sensor and the other lead to a clean ground on the engine or chassis. With the engine running, you should see voltage vary between around .2 to .8 fairly slowly at idle, maybe 2 or 3 cycles in 10 seconds. Now shut off the engine, but leave the key in the ON position (dash lights all on). Next, check the grey wire coming out of the car harness for continuity to ground (meter set to Ohms). It should have almost no resistance to ground (good continuity). Lastly, verify the two white wires have +12V (meter set to DC Volts) on the car side of the harness.

You didn't get any anti-seize compound on the heads of the sensors, did you? Based on the codes, it sounds as if wires are either swapped (hard to do, I know), loose, or the whole lot of sensors is bad. Were any of the wires faded or damaged in some way on the car harness?

Not all universal 4 wire sensors are the same.

The bank 1 after cat sensor on my 1997 has been replaced 3 times. Every 2 years it gets replaced because every 2 years it is time for a smog inspection. The replacements were the Bosch sensor sold by the dealer with the plug on the end.

This year I decided to go with a Walker made sensor, as I had it with Bosch. Walker makes several universal 4 wires sensors, but not for a 986. The only 986 sensor Walker makes is the "direct fit" which simply means it had the plug on the end.

Yet on ebay there was someone selling a Walker universal sensor for a Boxster for $20, but the seller could not give me the part number so I could look it up in the Walker catalog. Because if you look in the Walker catalog is says that the Boxster universal sensor is N/A. I then emailed Walker and an engineer explained why Walker did not sell a universal for the Boxster, only the direct fit.

So I bought the Walker direct fit on ebay for $109 plus $9 to ship.

I had checked out the Bosch universal sensor - but I had it with Bosch.

I should have the Walker sensor in the mail the next day or so. Will be interesting to see if it works and if it does for how long.

Thanks for the input towards this, guys... I'll hopefully get a chance to look at it this coming thursday or, maybe if I get really, really lucky, this sunday ;)

Schnell - Thanks for the input, and I'll run all the tests and see what I come up with.

Cheers!

Alright, everything seems to check out (on the car/wiring side), my guess is that the cheaper sensors just aren't compatible with the olde schoole (note the extra "e"s, for extra old-timey-ness) DMEs.. Since I really don't have the spare time to be playing around, I'm going to see if I can send back the sensors that didn't work for me. If not, Look for a cheap set of sensors here in the next week or so. I'm going to just buy the Bosch ones from Advance Auto Parts for $80 a piece.

BinaryC Hasn't gotten back to me yet, so I'm guessing that I'm just SOL.

Such is life, eh?

Cheers! :)

hey wonko, did you figure out your 02 problem? i was considering ordering the universal 02 sensors for my car

No, unfortunately I did not... I ended up ordering all four from Advance Auto Parts, getting bosche replacements... it cost $250 or so... I think that it may be an issue with the DME 2.5.5 (the one running the 2.5L engines). I don't have any real way of knowing/checking, though. if you want to try em, I can sell you the set for $100... I still have them sitting in their boxes.