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Quote:
Originally Posted by StegaDragon
@ steve99 it's the learned memory that is a factor not the actual code, the ECU learns the actuator response and movement, since Toyota won't let you re-flash an ecu unless there's an update the only way to make sure the vehicle doesn't return with an erroneous code is to replace the ECU
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The "brains" of thg ECU is a renasis SH72531 processor
more info see here
http://www.ft86club.com/forums/showthread.php?t=68328
the SH72531 is a single chip microcontroller unit that contains a processor ans some onboard ROM(flash memory) and some RAM, . The rom or flash memory area is where you flash your tune to and this is permanent till reflashed. The ram area is where ecu stores learned knock,fueling and other calibration data, ecu fault codes etc. All that area gets erased if power is removed for a short period.
So unless their is an actual hardware fault in ecu or its on board interface circuitry, then they dont need replacing, this is possible but unlikely.
Even "bricked" ecu is not actually physically damaged, it just had bad rom code written to it that has sent the processor into a loop or indeterminate state that is not easily recovered as it will no longer talk to the car obd port, unless you access the boot MAT area of the ecu by making physical connections direct to ecu circuit board and force boot mode .
Im not sure why toyota\subaru were blindly replacing ecu in early days, it may have been because the dealers , especially toyota did not have a flash tool to reflash ecu so they just replaced ecu with a new ubit with updated rom calibration
Their is still a TSB out that says replace ecu after extensive testing of other cam componentry, i suspect this is done as if all else has been checked then they suspect a fault in ecu hardware, but it does appear that in 99% of cases reflashing ecu to latest fimware will sort ecu problem, but quite often expensive cam actuator\sproket assembly needs replaceing and\or oil control valves , rarther than ecu
If you get cam codes rough idle outside warantee i would
1. Ensure ecu is flashed with latest compatable factory update in before 2014 this will be B01C or B01D
2. Do the cam sensor tsb re adjusting sensor clearance
Both of the above are quite cheap and easy.
3. If still no good do the other cam tsb which involves extensive testing and replacement of oil control valves, cam actuator\sprokets and if all else fails ectire ecu. This will be expensive and timeconsuming work