PO133 Rear Oxygen Sensor, replaced, still getting code

jallert · Post by **jallert** » 27 Jan 2009, 11:27

1997 850 T5: My check engine light came on. My mechanic gave me two codes for rear oxygen sensor (PO133 for generic code). I replaced it. A day later same code came back. ANy thoughts? I did purchase and install (this time) the Bosch pigtail. Seems wierd. I have lots of extra wiring that I just spooled and tied back with a tie strap. Thanks for the help.- JA

Post by **billofdurham** » 27 Jan 2009, 12:32

My book shows P0133 relates to the front oxygen sensor.

Bill.

jallert · Post by **jallert** » 28 Jan 2009, 08:01

Thanks Bill. Will double check, but he was using a volvo code reader. Mine is telling me PO133. What about disconnecting battery to let things reboot? I never disconnected the battery during the install. thx

Post by **billofdurham** » 28 Jan 2009, 12:41

It is best to disconnect the negative battery terminal before unhooking any electronic sensor wires otherwise the computer doesn't know it's in the system.

Make sure you have your radio code, turn ignition switch to 'off', at this point I remove the key as disconnecting the battery with the ignition 'on' can damage electronics. Disconnect the battery negative lead and leave it for about 30 minutes. Reconnect the battery and take the car for a run to allow the computer to relearn.

Bill.

Post by **pkc303** » 30 Apr 2009, 17:52

I have the same problem (Code P0133), and forgot to disconnect the battery when replacing the front sensor. I tried a known good front sensor, same problem. I bought one from IPD, same problem. Volvo service man tells me to replace both sensors. So, I get a Bosch and replace rear sensor. Forgot to disconnect power from battery again. Drive around, and get code P0133.

I'm waiting 30 mins. as per last post. We will see if I get code.

My question for the last post was did it work????

Post by **pkc303** » 01 May 2009, 14:53

Well, I tried all of the suggestions above, and to no avail. The CEL comes back on, and the code remains the same. P0133. I'm open for any suggestions.

Post by **misha** » 01 May 2009, 17:03

If you reseted code and it comes back again with new sensors,then i think it could be some vacuum leak.But if there is a vacuum leak then ecu should display codes for both sensors,front and rear.

Post by **pkc303** » 01 May 2009, 18:22

I'll check for a vacuum leak, and also trace the wires for bad connections. Thanks.

Post by **pkc303** » 04 May 2009, 19:13

Ok, I fixed it. Our 1997 850R could not pass emissions testing. It had high HC and high CO, caused by unburned hydrocarbons.

Reading late the other night, I found a TSB number 824 dealing with a pulsation damper to damp shock waves in the fuel injection system. It's job is to reduce the shock waves in the fuel rail when the injectors open and close. These can produce the incorrect fuel flow at certain engine speeds. It goes on to say that it can affect the heated oxygen sensors (HO2S), thus our P0133 code, which points to a slow response in the O2 sensor before the cat.

Anyway our car has a vacuum line running from the vacuum tree just above the idle air controller over to the fuel damper just under where the fuel rail starts feeding the injectors. The elbow was deteriorated to the point that the line no longer held a vacuum. I have temporarily placed another line in, and it fixed the problem. After driving another 70 miles to reset the modules, no CEL, and it passed emissions test this morning. I have new rubber on the way from Volvo. I'll include pictures so that you have an idea what to look for. This was the final code of about 15 when we purchased the car two months ago.

Post by **misha** » 05 May 2009, 11:58

I'm glad that you're solved problem!