Still trying to resolve the mystery code causing my 1990 xj 6 transmission to remain defaulted to limp mode. replaced tcm, decoder module , clean rotory switch & potentiometer.. back probe most of the in / out @ tcm. no trouble code on vcm. I cannot find anyone that has working jdu / pdu dtc scanner..
Is this the only way to retrieve dtc for transmission in my car ? Anyone know of working jdu / pdu dtc scanner near seattle washington ? local expert says replace tps,, but I backprobe tested it @ tcm and it is .30 - 5.00 v .. within spec or very close as far as I know. Thanks to motorcarman I have the wiring sckematic for tcm & associated controls. Really could use a scanner though!!

 

tps should be .6v at closed throttle, that may be your issue. Haynes says .5 but from experience it needs to be at .6v

 

JDS is a REALLY old system that will probably not help and I doubt you will find a functional unit.

PDU is the only system that will work for the ECM,TCM,ABS for the XJ40. WDS was supposed to be a replacement and we got the cables to connect to the car in the WDS setup package but the software NEVER materialized.

Keep looking??

bob gauff