Re-learn procedure
 

Has anyone tried this relearn procedure after a major change:

* Set parking brake, start engine in "P" or "N" position.
Warm-up vehicle to normal operating temperature or until
cooling fan cycles.
* Allow vehicle to idle for one minute in "N" position. Select
"D" and allow engine to idle for one minute.
* Accelerate at normal throttle position (20-50%) until vehicle
shifts into top gear.
* Cruise at light to medium throttle.
* Decelerate to a stop, allowing vehicle to downshift, and use
brakes normally.
* Process may be repeated as necessary.

If so, does anyone know if the car has to be started cold or can it be started warm in step 1?

Re: Re-learn procedure
 

If you have to relearn the maps, then it means your battery has been disconnected for at least an hour.... which is enough to cool the car back into open loop. The entire relearn process is done in closed loop when the car is warm, and the O2 sensors are hot enough to start detecting your exhaust oxygen.

This procedure is kind of useless, since most everything they ask you to do is experienced in regular driving anyways.

Re: Re-learn procedure
 

My impression is that this sequence will immediately reset the closed loop parameters and provide a decent starting point for them instead of waiting the 30-40 drive cycles it normally takes for the closed loop parameters to re-adjust either from current erroneous values (if you just replaced an O2 sensor, for example) or from default values (if you disconnected the battery).

Re: Re-learn procedure
 

:confused:

What resets the parameters is leaving the battery disconnected.... and they already have decent starting points.... default from factory.

The procedure outlined is so the ECU can relearn more efficient fuel and timing maps during

a) Idle, no load
b) Idle, TC load in gear
c) Normal acceleration
b) Normal sustained cruise

So my point is, this is experienced in normal everyday driving. LOOK at the instructions closely... "Process may be repeated as necessary".

So if you want, you can be the guy doing laps around his neighborhood trying to efficientize his car, OR you can just drive through town on errands when you need to, and it will be almost exactly the same and easier for you. You may lose $3 in fuel mileage, tops... I promise.

Re: Re-learn procedure
 

So it has been about a month since I replaced the faulty O2 sensor and my long term fuel trim numbers are still high for that bank. I got a highway cruise value of about +14%. The other bank is petty close to zero. I ran a can of seafoam through the fuel system just in case it was a clogged injector but that didn't help. I am thinking of going to something more powerful like Redline SI-1 or the concentrated Chevron Techron. Any other ideas why the fuel trim would still be high? Maybe I should disconnect the battery for a half hour and just reset the whole ECU?

Re: Re-learn procedure
 

Would this be the first time you did it since replacing the O2?

Re: Re-learn procedure
 

Yes but I guess I assumed that the ECU would have re-adjusted to the new O2 sensor by now. Bad assumption?