we had the infamous check engine light on a 2001 Volvo V40. P0133 or something, the one about O2 sensors. We replaced the O2 sensors this morning, and the mechanic said that we have to drive it about 50 miles before the internal computer will reset, even though the check engine light is gone. Never heard of this... but ok... he won't re-test our car for emission check, so what can I do. Drove 50 miles.

We came back to the shop, he plugged in his OBD II scanner, but he told us that it was still not "READY" to be re-tested yet!? After a full day and 50+ miles of driving after the O2 sensors repairs!? What is he talking about? He said he can't test the car until the internal computer is reset. The OBD II scanner that I owned shows NOTHING. He said he doesn't know when it will be ready, just come back every day and he'll try.

??

 

BTW, some of u asked if this mechanic is trying to charge me more $$, but all this is actually free since HE's the one who replaced the O2 sensor after the first test. Here is the story:

Yes, I paid only for the emission test. It first failed, with the P0133 code. So the dealer (weird situation, the small independent dealer is next door and friends with this mechanic shop) simply paid this mechanic who replaced the O2 sensor. We did not have to pay for it, only paid for the initial emission test of $30 or something.

The SAME mechanic (who replaced the O2 sensor) is now telling us the car is still not ready to be re-tested. He can't tell me to replace the O2 sensors again because he was the one who replaced them! The check engine light came on, and I plugged in my own OBD scanner, saying P0133 again. Is this what he is talking about? The code will keep coming back until whatever this internal computer is reset and recognizes the new O2 sensors?

Thanks.

 

Sorry I can only use one line answers do to forum F***** up. The computer needs to see all systems free of faults.

 

What is that internal computer (besides the light that my OBD scanner is able to reset) when is the computer gonna be reset?

 

The internal computer is the ECM. Sometimes it takes a while to reset. But if they had the Volvo software for OBDII they could reset half of it.

 

UPDATE: Tried all the battery, fuse disconnections. Tired putting on 100+ miles, and 4 days of driving. Nothing can reset the Check Engine Light.. if anything, the idle speed is now under 1000 RPM, a bit odd. I used my OBD scanner to reset the light, and of course, 3-cycles later the internal computer still detects whatever P0133 O2 sensor problem, and the light came back on.
Dealer and mechanic finally conceded that maybe the O2 (Bosch, brand new - we saw them opening the box and installing it) is defective. Ordered new one, and will re-install tomorrow.
I just want the damn car to pass emission!

 

Keep us updated.

 

Is it aftermarket o2 sensor? Also after replacing an O2 sensor the adaptation have to be erased.. unfortunately the dealer have to erase it by going into fault tracing code ECM-16and reset adaptation from there... if there are software upgrade to the ECM it should be done also. I hope this help.