Hi All
So when/if my battery runs flat - The time for ECU to 're-learn' my driving characteristics is much longer than the normal 10-15 km .. typical 250-300 km before it run normal again..
Can anyone tell Me Why ? Or Is there a Way / tool to re- program ECU after battery disconnect , so re-learn mode can be skibed ?
Btw I have a XKR 99’ with 2006 4.2 Block .
Thanks

 

An '06 engine (and presumably an '06 ECM) in a '99 body makes this question complex, perhaps.

If this is what you meant, how much of the electronics is '06, and how much is '99 (i.e. you cannot just plug a '06 ECM into a '99 Network and vice versa)? Transmission an '06 too, instrument panel, etc?

 

Look at the OBD monitors to see which ones have not set quickly.

That may give you ideas about what may be wrong.

Each one may have its own drive cycle so be sure to do those.

Also look at the vital sensors - see OnBoardDiagnostics.com - Engine Basics for ideas - to check the values make sense.

Then check the fuel trims in case they reveal anything.

Most likely there is a problem, even if it's only something nearly out of range.

 

If you have or a friend has a jump start kit, just hook the positive up to you positive and the negative of the jump start to a bolt on the car and change it out.
Should hold all the information in the ECU. Be sure and have the jump start + on the outside of the clamp so you can take it off and put it on without losing your connection to 12V.

 

Hi Dale_ Yeah it’s bit complex - But only the ‘block’ is 2006 4.2 - all other incl all electronic is 99’

 

That's good. So, what are the symptoms you are seeing from the lack of 'relearning'? (Idle, shift points, etc)?

 

The learning you are talking about is the mechanism of short term/long term fuel trims. Basically, the ECU has a basic fuel table per bank telling the injectors how much fuel to inject for a given load and rpm. This is when everything is perfect, i.e. no air leaks, all sensors working ok. Thanks to the upstream wideband O2 sensors, the ECU is able to get feedback on this base table and perform adjustments, i.e. fuel trims. Because the O2 sensors have a bit of a delayed reaction, the feedback cannot be live, but is separated into long term and short term. The long term trims are superposed to the base fuel table. The short term trims are the closest thing to a live measurement. The learning mechanism consists of calculating the average of these short term readings, and then update the long term trim every 2 minutes. In other words, each position in the matrix of fuel trims (indexed by load and rpm) needs 2 minutes of short trims to update the long term trim number at the same position. My take is that for some positions like idle, the car spends plenty of time and the short term trims quickly average zero. For other positions (take your pick, 2800 rpm and light load?) there is hardly any time spent and the trim takes a much longer to adjust.

There is a written procedure out there that describes the steps after disconnecting the battery. It obviously lists the window reset, but also list an interesting follow up: basically you have to put your foot on the brake (stay stationary the whole time), put the car in "D" and run the engine at a couple of frequently used rpms for those 2 min. This would accelerate the learning for these 2 rpm and high load, and accelerate the learning for getting off the line.

Of course experiencing a big difference in drivability with trims reset could be an indication that your car needs high trims, i.e. has either a bad AFM or air leaks. A smoke test would likely be helpful.

Best of luck, keep us posted.