I just replaced the upstream oxygen sensor, (P0135) why am I now getting code P0134 (no activity)

SOURCE: 2001 Chevy Venture 92K miles - code P0134

dunno bout rotating the engine to put those plugs in, but the O2 sensor is right in the way as your arm is stuffed up behind the engine (plugs have to be done from below at the back) so I wouldnt be shocked if you found a disconnected O2 sensor that was never reconnected, or a damaged wiring loom from rough contact with the mechanic's arm. Those plugs are very hard to change so go easy on the guy!

Dave C

• 1050 Answers
• Posted on Mar 31, 2009

SOURCE: P0134 Error Code

The code refers to an oxygen sensor that is no longer detecting changes in fuel delivery by way of sensing exhaust oxygen content. Bank 1, sensor 1, tells you which sensor is bad, in this case, it's the sensor that is mounted before the catalytic converter, on the rear bank of cylinders as you look into the engine compartment. It would really be a good idea to change both pre-cat O2 sensors at this point as they are both twelve years old.

SOURCE: codes

Your sensors are reading correctly so leave them alone. What you have is a fuel delivery issue. Your MAF sensor is telling your engine to lean your fuel mixture. You need to remove and clean or replace (is better) the MAF. But first replace your PVC valve and clean your ERG valve.

Brad Kirby

• 547 Answers
• Posted on Mar 03, 2011

SOURCE: check engine light code P0171

That code is a good O2 sensor reporting a lean condition. Lazy people and part stored just say it is the O2 sensor because they don't know how to fix it. Bank 1 is the side of the engine with the number one cylinder. That bank has a lean condition meaning it doesn't have enough fuel for the given amount of air. Since this is only affecting one side of the engine, that narrows down possible causes. Possible causes would a leaking intake gasket or a broken vacuum hose on that side. Since both sides get fuel from the same pump and rail, this wouldn't be a fuel pump or regulator issue. It can, however, be an indication of a bad fuel injector on that side of the engine. The MAP sensor also couldn't cause this code because, just like the fuel pump, that MAP sensor works for both sides of the engine and the code is only for one side. I would drive it for a couple more days to see if you get any additional codes that could help point you towards the actual problem. In the meantime, I would check for vacuum leaks (look at the rubber hoses and listen for high pitch hissing or sucking sounds.)

SOURCE: my 2000 dodge grand caravan

the codes for the oxygen sensors and egr valve dont neccassarily mean those parts are "bad". O2 sensor codes are usually caused by a different problem all together. There job is to monitor oxygen levels in the exhaust to make sure it is clean enough to meet emmisions standards. If you have a vaccuum leak, misfire, or a fuel problem those codes can show up. The egr valve recycles the exhaust gas in another attempt to clean the impurities. If the vavle was truley bad it would of affected the was the vehicle idled and drove on the highway. The egr activates when the throttle is depressed it opens at 1/4 of full throttle and closes at idle. Though they get pretty dirty the usually dont just fail under normal driving conditions. I would say that po171 code which if i remember right is a o2 sensor lean code, is showing now you have a tune up that needs to be done or a leaking intake manifold. A dirty or failed pcv valve can also cause that code because of it being operated by vaccuum from the engine. If any vaccuum is lost or restricted the hole combustion process will be incorrect.