Hi,
I got the error code P1646, changed the specific oxygen sensor. How long does the error stay displayed?

 

With a 'stored' error code, you have to clear it using a suitable scantool/code reader.

Graham

 

Er... not quite so.

If fixed, the PCM will turn off the MIL after 3 warm ups with no error. (That may mean on the 4th.)

(Actually required by law - surprised me!)

The code stays harmlessly stored (e.g. won't affect smog checks) for ages but eventually is auto-erased.

As a result, NOT clearing the code is often the best plan as it leaves the OBD monitors used for smog checks as they were, whereas clearing the code clears those and if they don't set again in time for the next smog check life can be painful.

(It's true, though, that the OBD monitors SHOULD set quite quickly. Just they don't always...)

 

I took her for a short spin after changing the O2 sensor and the MIL stayed on.
Disconnected the battery for 2 hours, thought that might clear the MIL (I don't have an OBD reader).
Went shopping, a 20 kms drive, and the MIL was gone.
And it has stayed so until now.
Thanks for your answers!

 

John,

The MIL will go off but I thought the P1646 code will remain stored forever unless it is deliberately cleared. Have you found an OBD technical source that states otherwise?

Graham

 

I can't recall when I first found out but it's all over the net

Good enough?
Introduction To OBD II

A bit more definitive
https://www.gpo.gov/fdsys/pkg/FR-200...df/E9-2405.pdf