What exactly happens when you removing the -negative battery cable? I know the computer then relearns your driving habits but what does it do?

 

The PCM stores operating parameters and data in static RAM. Static RAM requires continuous power in order to keep the memory valid. Removal of power to the RAM causes it to reset to its default state. There is a capacitor on the input power feed to the RAM that provides for up to several minutes of "back-up" power. It takes several minutes for this to drain down. That is why instructions typically say to leave the battery disconnected for 10-15 minutes to ensure a complete reset.

Steve

 

The PCM has to perform a complete drive cycle that takes readings from all the monitoring systems to capture driving/performance data and make sure all systems are functioning properly.

Sorry Steve, guess I was a minute too late.

 

After 15 minutes without juice, the KAM is erased (Keep Alive Memory) - Upon reconnect you fall into "Adaptive Strategy" mode. ie fuel trims and tran tables . It's a little complex. EEC likes to toy with the fuel ratio at random. It does this to run complex math equations. She is calculating how much fuel is required to reach certain lean or rich states.

Why? Because playing this cat and mouse game with the fuel ratio allows us to fine tune the engine parameters in other strategies. Confused yet? EEC cuts back on the injectors for a spit second and counts how long it takes for the HEGO to report back a lean environment. EEC leans and enriches at different amounts and get back different numbers. These numbers tell EEC if the engine needs a tune up, or if you’ve added a performance parts and allows us to actually alter the fuel amount delivered.

What do we do with those numbers EEC collected? Well there is a Table called “Adaptive Fuel Table” (makes sense huh?) This table is used as a multiplier, it is held over the master load table. It then multiplies each number in the master table to get a better control of fuel delivery over time. In a computer that has been just connected to the battery it is full of “1’s”, if you multiply the master table by “1″ you get the same number. I’m not good at math and I understand it, 14.7:1 X 1 = 14.7:1, simple!.

After many days of driving on the highway it begins to fill with multipliers like “1.2’s” and “0.9’s”, which will alter the master table. Don’t believe me? 14.7:1 X 1.2 = 17.6:1, and 14.7:1 X 0.9 = 13.3:1, and we just fine tuned our fuel curve without doing anything special.

Isn’t that cool? Well not always, this entire technology depends on the Oxygen Sensors being fresh, clean, new, and in good condition.

Damn! You both beat me!

 

jbrew, is it then resonnable to say at 155k plus miles with(no CEL){this time} that changing the o2 sensors will save gas????

 

It's possible, that really depends on your driving habits more than anything. On average , if your getting less than 14 mpg then somethings not right, unless you pulling load.

Good maintenance = Good mileage as well .

Plugs, air filter, clean MAF, clean TB and Plenum ports to name a few areas to look at. The O2's CAN make all the difference in the world and has, but they can't do it alone.

With your miles I would think about updating with OEM Bosch replacements. It's a good idea to use exactly what came out of there stock.

 

I suddenly feel like an immigrant.

Can you translate English back into English?

 

Start a new thread

 

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