| First, let me explain the basic way in which the ECU works. The ECU (also know as the ECM, electronic control module) contains a preprogrammed main processor. This is a microprocessor which is custom programmed by the manufacturer to do a certain task and can not be changed without replacing it (this is NOT the eprom chip such as a JWT chip). This is the brain of the ECM. There is also no way of reprogramming it using programmers such as the ones used for programming eprom's (the JWT chip). The eprom chip (JWT chip) only contains set information which is used to feed the main processor when asked. This chip is not written to or rewritten when being used in the electrical circuit. It is only a chip that holds specific values and delivers those values when needed. This is a common way microprocessors work with eprom chips in all kinds of equipment. The microprocessor is monitoring the information being fed to it by a series of other chips and devices which are being fed to them by all the sensors in the car. Depending on the condition of the sensors the microprocessor asks the eprom chip (JWT chip) what to do under those conditions. If the microprocessor fails to receive information from the eprom chip or it is notified of a critical problem it is programmed to resort to default values. This is what people refer to as being in limp mode or safety boost.
Now for the JWT safety factor.
When there is a critical problem such as detonation the microprocessor turns off communication with the eprom chip and uses it's own internal information or safety maps. At that point the car is in limp mode (also know as safety boost) and does not require any information from the eprom (JWT chip). There is no safety map needed to be accessed from the eprom chip under these circumstances because the microprocessor turns off communication to the chip. The safety map for critical problems is in the microprocessor, not the eprom (JWT chip). EMS's (or engine managment systems) which completely replace the ECU have programmable safety maps.
So in short, the JWT chip is safe because there is no safe information that is needed to be programmed into it. The safety maps which save the engine due to critical problems are in the the microprocessor.
The secondary map which is not needed for safety is a secondary map used for certain conditions which no longer apply due to the changes in the primary maps. JWT insures that the system is constant in the way that the secondary map is programmed. Messing with this map could cause a problem and is best left untouched. BTW, I used (JWT chip) as a reference to make it easier to follow my explaination.
;)
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I think I speak for most when I say "We don't give 2 sh!ts" (n/m) - YugoBernie (NoVA) 11:40:06 01/15/03 (4) |
