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Originally Posted by Trevor
Joe,
As a result of this arrangement, the same TCU could be used for both systems. This would appear logical and confirmed by the different solenoid configurations, as is used to operate clutch, or alternatively centre differential as are involved.
On the basis of this, it would seem illogical to propose that there is a difference between the JDM and Euro systems, when the only requirement is the provision of a manual switch, for power mode in the JDM system. This surely would not involve extensive circuit or software changes.
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Hi Trevor
Your logic is good, and we have already gone down this path of assuming they should be the same, or did not need to be different. In practice they
are different, and some of this difference is down to the use of a different speed sensor yielding a different pulsed signal. The control circuitry has to interpret these pulses [from the two different types] and Phil has postulated [correctly as I see it]that some of the mapping in the different TCUs takes account of the different final drives the markets come equipped with to determine road speed.
In my own case, I took it a step further and fitted a JDM TCU to my UK car. It did not work properly, the odometer was flying forwards at an impossible rate, about aircraft speed.
Another clue to the differences would be Pin 4. When earthed in the UK type, it turns on Econ mode, rather than Power. Econ is the diametric opposite of power. When switched on, it denies access to the power map, and maintains the car driving in Normal all the time. As the input pins are different, so the internal circuitry must be different. Not a lot, I'm sure, just different.
It does appear that now that Nomake Wan has grounded the Pin 4 in the US type and switched on Power, that this confirms the US software is at least similar in that respect to the JDM software. For those same model years.
It wouldn't surprise me if the later years that don't light up the power light are different again, because of OBD 11 circuitry.
Great progress, I'm thinking!!
Joe