Thread: interesting problem...

Hi JMK
Towing the caravan would give the engine a great workout removing any varnishes or glazing form the bore.It will improve horsepower so its not your imagination.
Andrew

Originally Posted by Tombie2

Nope!

Factory fix for surging issues in some vehicles....

They inverted the mapping in the ECUs to remove throttle sensitivity in High by flipping the internal settings....

Mines like that.... (Hard chipped ECUs only)

Hi Tombie As Well,

So, does this mean these vehicles are extra, extra touchy in LO? Seems an odd 'fix'.

And from your later reply, it seems this inversion of the HI/LO switch input is hard-coded into the ECU - and it doesn't even get 'restored' to normal when the chip is upgraded? (like the BD upgrade JC had done on the vehicle in question).

It seems the SLABS/ABS read the state of the HI/LO switch 'normally', so only the input to the ECU needs to be 're-inverted'. Think I've sussed out how to do this quite simply. Do you happen to know if the HI/LO sw. is definitely a 12V circuit, do you? That is, it's not a reduced voltage (e.g. 8V or 5V) circuit for some obscure reason, is it? (I can measure one next week at JC's but it would be handy to know this weekend if possible.)

Thanks,
Ian

The little add-on circuit did the job on this vehicle. Inserted into the loom just before the multipin plug & socket adjacent to the main ECU in the RHF corner of the engine bay.

It "re-inverts" the HI/LO signal to the engine ECU so that it reads the switch position in reverse but, as a result, uses the correct map in HI & LO. At the same time the SLABS ECU still 'sees' the switch position correctly and so, Hill Descent etc. still works properly.

Still confused as to how they'd do it and why the factory would consider this a 'fix', if it resulted in really lousy, super-touchy throttle response in LO. Any clues Tombie?

Ian