Intermittent O2 sensor fault?

[d00df00d]

A few days ago, my car lost a bunch of low-end power and got jerky on throttle transitions. Then the CEL came on. A generic OBD II code reader showed P0134, indicating that the pre-cat O2 sensor for cylinders 1-3 was not functioning. I had just replaced that sensor about 4 months and 7,000 miles ago.

Then, just yesterday on my way to Pep Boys to buy a replacement sensor, the CEL disappeared and the car felt normal again.

Any ideas as to what might cause an intermittent O2 sensor issue?

 

[dparm]

Remove the sensor and clean it. You can use electronics cleaner.

 

[Vikas]

What is the brand of the sensor? Was it OEM with the oem connector or you did a splice job? The code indicates electrical problem with the sensor. If it is OEM Denso or NGK, I would be shocked.

 

[d00df00d]

It's a Bosh, plug-and-play.

 

[wallyuwl]

Originally Posted By: d00df00d
Any ideas as to what might cause an intermittent O2 sensor issue?


What is causing the problem with the sensor is that there is probably a problem with the sensor.

 

[d00df00d]

Touché.

I meant to ask whether anything other than a defect in the sensor could cause the issue.

 

[tomcat27]

I got two bad Bosch's that were worse than the O2 sensor I removed. went with OEM.

 

[Vikas]

Complain to Pep Boys and exchange it for an OEM (likely to be Denso or NTK). What was the code which necessitated the previous replacement? Can you trace the wires all the way from the sensor to the ECM?

If the previous code was the same, then it is more likely that you have a problem with wiring than with the sensor. Probability of a lose contact inside the sensor is lot less than some corrosion (or chaffing of wires) at the connectors.

- Vikas

 

[artificialist]

Originally Posted By: d00df00d
It's a Bosh, plug-and-play.

Was the OE sensor a Bosch?

There have been numerous problems with cars that came with a Denso or NTK, and had a replacement Bosch sensor installed.

 

[ltslimjim]

Wanting to find out how this turned out.

 

[d00df00d]

Thanks for the reminder.

The car passed inspection after this post, and hasn't had a CEL since. Since then, I did check the fault codes on a whim and found an O2 sensor code, but that may have been stored from previously. I should check again...

 

[ltslimjim]

Well, at worst it seems to be an intermittent issue. Bosch sometimes makes the universal(as does Denso IIRC), which can be fine post-cat, but pre-cat it's good to find as close to OE as possible. Just a thought, if it comes back.

EDIT: I was going to add info about Amazon's listings for your vehicle. Is the pre-post cat the same sensor? Some reviewers on Amazon say their Bosch product arrives as an NTK labeled sensor, FWIW. Assuming you have post-cat sensors.

 

[HerrStig]

Even good sensors can get "lazy" and mislead the ECU as to what the exhaust A/F content is. Toyotas from 97 through 2001 (at least) have had this problem, after a shut off and ten to 15 minute restart. The sensor is still sending the hot engine reading when the engine has cooled enough to need a richer mixture for a short time. Result, stumble, backfire, and stalling until the sensor "flips". I found full throttle would bypass the mixture "calculation" and also shock the sensor into the right reading. Can't do that in traffic, though. Did some gunk get on the sensor on installation?

 

[mechtech2]

O2 sensors rarely go good/bad with hard and distinct problems .
They slowly go bad, or just puke.
This sounds like wiring, connectors -things like that.
Even all the way back to the computer.
So check the O2 wiring first -shorts sound likely, or intermittent connections .

Also check and clean ALL grounds and hot leads, and where they seat.

Often there is a separate ground for the computer.
This can fix all sorts of things, and if not, is GREAT preventative maintenance. It is a good step as a solid base to go from.

 

[ltslimjim]

^This. Good all-around maintenance tips relative to having clean/tight grounding wires and hot leads. Especially important to verify wiring is fine at sensors which have thrown codes up.

Some apps are known to have a wire slightly loose in a harness, for example, if swapping out components and need a gentle tug or inspection to make sure none of the wires into the harness and at the connector itself stand out compared to the other wire(s).

 

[Vikas]

+1

There are no moving parts inside an O2 sensor! So if you have an intermittent fault, it has to be in the wiring. The wire inside the sensor could be broken (i.e. faulty sensor) but probability of that happening is rather low.

Most likely the wire is rubbing on something and the insulation has worn out and is now shorting randomly. This will NOT be fun to diagnosis :-(

 

[mechtech2]

Tapping on stuff like a MAF sensor, coil, connections, etc., with a screwdriver handle can show up problems.