Hey guys, newbie to the forums here but not to cars.

I just bought my 96 SE for $700 with a dead #1 rod. I have since replaced the engine with a 98 Bonny. Everything went nice and smoothly and engine runs great. However I had a code pop up orginally as a p0133 for o2 sensor slow response. So I bought a new o2 sensor and installed it and I have a p0134 for no activity. When monitoring the o2 mv, its just .450mv and not switching. So I figured bad o2 out of the box (bought new on ebay) So I put the old o2 back in and now same thing and same code now only a p0134. Im guessing its a wiring issue problem. Vehicle drove fine when had code p0133 in it and then with thew new o2 sensor and p0134 present code the veh idle dips and surges when slowing down or taking my foot off the gas, the veh has also stalled as well. I am guessing the car is running richer than normal since it has no o2 signal but I do not know if the stalling is related or not. I just was wondering if there are any common problems to look for before I start checking wiring and such (I heard about the driver footwell grounds and will check that as well)

Has this happened to anyone before?

welcome to the forum! be sure to post in the introduction section too it helps with more visibility


one question what brand o2 sensor did you buy?

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2000 ssei gone but not forgotten

Current fleet:
2009 G8 v6, 2009 Avalanche LTZ, 2013 Volt

Try disconnecting the battery for a few minutes - force the PCM back to learn mode.
Scan it after - just to be sure if it's reading or not.

Thinking that the old was was reading constantly high - so it wasn't running rich - but not right either.

Also, make sure O2 sensor line is not cracked or rubbing up against the exhaust, check the connector too.

thanks for the welcome and fast replies guys. As for the brand I have no idea, I know its not a bosch or delco, probably some cheape chinese one.

I actually replaced the battery the same time the o2 sensor was changed out as well so it should have cleared the memory as well.

ok, also it looks like there are a lot of different o2 sensors for the different years. is it possible that you got the wrong year of sensor?

if you decide to buy another DO NOT buy bosch, they don't agree with 3800's I believe the recommended brands are either delco or denso

_________________
2000 ssei gone but not forgotten

Current fleet:
2009 G8 v6, 2009 Avalanche LTZ, 2013 Volt

Yea I did get the correct sensor for the year the 94-96 have the old flat style connector and the late 96 up have the "cube" type connector. I checked and I have good power and ground through the connector, however through the trouble tree diag I did get some varances in readings and traced wires to pcm and ohmed the wires and they ohm'ed out okay. Any ideas? The only other thing it can be is the pcm but im not fully convenced of it. I still havent cleaned or looked at the wires in the driver foot well area. Are those connections grounds for the pcm or bcm? and where exactly are they located at?

You should start by testing for power and ground at the sensor connector. Im thinking you may not be getting one or the other.

I did verify it has power and ground at the connector pins on the pcm side. I have not left it plugged in and back probed to make sure its getting to the o2 sensor yet. However all the pins look good and not bent or loose or anything.

Then you should check continuity of the signal wires from the sensor connector to the pcm connector. Should be 0.0 to 0.4 ohms.

yea i did check the ohm reading of both signal purple and tan wires back to the pcm. It read .3-.4 ohm. According to GM spec anything under 5 ohm is good..but 5 ohm seems kinda high.

I've a 95 ssei, not a 96se so I'm not sure...

Maybe you are physically checking the wrong sensor - are there 2 banks on the pcm? 2 O2 sensors maybe...

8th Vin Digit K or 1 - you have a downstream one (after catalytic)
Downstream usually around 450mv, moves little.
Upstream shoud swing steady 100-900mv - like a sine wave.

Wires crossed maybe? Dunno - just ideas here.

No this is the upstream o2 on the rear manifold. The rear o2 sensor mv are switching slightly when monitoring with scanner. the front o2 is a steady .450-.445mv which is just a reference signal sent from the pcm.

Well all your test results say its a bad pcm, but personally I would try a store bought, good quality O2 sensor first.

Try a Denso direct-fit from Amazon. Can't beat the price.

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2012 Chevrolet Cruze Eco - Current car

1999 Buick LeSabre Custom - Former car

Learn from the mistakes of others, that way when you mess up you can do so in new and interesting ways.

My MAF sensor just went on my Bonneville.
When scanning, the O2 readings were barely moving. I unplugged the MAF and the scans looked decent.
Now I know the actual air-fuel is buggered up by the bad sensor but the PCM was reacting to the bad sensor and it seemed to be affecting the way it read the feedback from the others.
So... long story - BUT - check your other sensors - maybe looking at a different root cause here, and go with a good O2 sensor...

Thanks for the help and suggestions guys.

Just figured I would post a fix in case anyone else comes across it in the future. It was indeed the pcm. Got a replacement one in and programmed and now both o2s are reading and flucutating nicely.

Now since I decided to go wot on it during the test drive and brought it back there is now a nice slight lower end knock and its down 20psi of oil.... Fix one thing break another..always seems to be my luck.