I had a similar problem with a JZZ30, 1J. would randomly throw code 52. So I just split the knk 2 signal, and ran than into both pins of the ecu. It worked for a while, then I noticed the same fault coming up at a later date, but without the huge ignition retard whilst driving. Anyway, replaced all the caps in the ecu, and all has been good so far.
Just on a side note, does anyone know if it possible to retrieve codes via the rectangular diagnostics box on 1U ? it doesn't have the oval plug after the engine conversion. It has Pin 'W', which I believe is the CEL wire, but voltage when in diag mode seems very low to trigger a check light.
Brett