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oxygen (o2) sensor codes S70

Hi to all, I was driving the family 1998 S70 (non turbo) and out of the blue the "check engine" light turns on. I was near an auto parts place that will retrieve the code. I got two codes. P0133 and P0140. From the time the light went on to the time the codes were retrieved about 5 minutes of driving went by. Two codes in five minutes seems a bit odd to me. The codes point to both different O2 sensors. How likely is it for both O2 sensors to go bad in a five minute period?

I am wondering what are the odds that both of these are valid? Could one be "sympathic" to the other ?

My searching on the net tells me P0133 is the front O2 sensor slow response and P0140 is the rear sensor no activity

A look in the Chiltons manual (all I have, granted not the most authoritative source of info) tells me P0133 is "front heated O2 sensor too slow Rear heated O2 sensor compensation" Chiltons states for the P0140 code "rear heated O2 sensor , check"

I have seen many posts about aftermarket (bosch) vs original, the pros and cons of splices. Also found some info about "new" originals that have a "different/improved " wiring arrangement. I would like to know more about the new wiring arrangement if anyone can provide the details.

I am very much interested in suggestions on the best approach to figuring this out. Dealer parts seem pretty pricey, direct fit a bit more reasonable, and splice type least expensive. What I want to avoid is getting pats I really don't need in the first place.

I also found a bunch of info on vacuum leaks and O2 codes, Best I can tell this only applies to turbo models. Can anyone verify this please?

Also spotted one post that states it is possible to clean them and return them to service. Anyone got any experence doing this?

This group has been a great help to me in the past and I very much appreciate any help. Thanks JR

Reply to
jr
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Codes and fault tracing are common between turbos and non turbos. Vacuum leak codes are more likely on turbos because they both stress their system more (temperature and pressure) as well as having a somewhat longer and more complicated system.

The new wiring arrangement includes an extension harness which adds a loop between the engine harness and oxygen sensors, to "prevent contamination from reaching the oxygen sensor's reference air."

These codes most likely both point to the same problem, most likely vacuum leaks. However, other things can cause these codes, including low compression, fuel pressure too low or high, leaks in the exhaust between the engine and catalytic convertor, as well as one of the oxygen sensors.

Reply to
Mike F

Sounds like I may be busy tracking this down.... I will try the vacuum system first as it sounds like the most likely cause. The tubing for vacuum looks like 4mm. Are there other common sizes used in this model car? I don't expect to hear a vacuum leak, Sounds like outside of getting lucky and actually seeing a defect, I will be replacing all vacuum hoses. Any individual hoses more likely than others to start with?

Would leaks in the exhaust system result in a noticable increase in noise?

Should I find the problem, currently I lack a tool to clear the codes, will the codes clear themselves after some particular amount of driving or some number of start cycles with out the fault present?

Thanks for the guidance JR

Reply to
jr

The vacuum hoses are generally plastic pipes, with rubber elbows on each end to make connections. Usually the rubber elbow deteriorates, and the problem is obvious. There are a bunch under the plastic cover over the throttle pulley, and sometimes one at the front end of the intake manifold behind the power steering pump where it's hard to see.

Exhaust system leaks cause noise, but often someone with a noisy exhaust won't think there's any possibility that is related to the problem, and so won't think to mention it.

The light will go off after 3 roughly 30 minute trips after a cold start, assuming the problem is fixed, at least mine does. However, vacuum leaks screw up the adaptation, so it may be a good idea to reset the computer by disconnecting the battery for about 30 minutes. This will also turn off the light, just be sure to have your radio code handy.

Reply to
Mike F

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