Trouble code help, tranny related

[Agent-Smith]

So I pulled the codes from my 1994 XLT with 4.0 and I got a reading of:
566 - 3/4 shift solenoid circuit
629 - Torque Converter Clutch circuit failure

Has anyone else ever had these and what are the possible reasons for these to come up? The truck still seems to drive and shift well but I'm not sure it shifts into OD. Thanks for any and all help guys.

 

[MrShorty]

If I assume those are KOEO codes, there are basically two possible causes: Either a full open in both circuits, or a short to ground in both circuits.

Where you have codes for both circuits, I'd start with the part of the circuit they have in common: namely the red wire from the EEC relay to the solenoids (they share a common power supply). This should be pretty easy to diagnose with a wiring diagram and a voltmeter.

If they are CM codes (KOEO pass), then it's going to be the same sort of electrical fault (open or short to ground) except that the problem is likely intermittent, which will complicate the diagnosis a little.