LCAM-01XA
Full Access Member
That one has me stumped - I was out with my small truck ('90 F350) today and happily coasting downhill with the converter unlocked (like they all do from the factory), when all of sudden the tach jumped about 200 rpms and immediately fell back down to where it was before, and when I hit the bottom and tried to lock the converter she'd have none of it. However, when I dropped her down into 3rd she would lock properly. No flashing OD light. From a standstill no excessively hard upshifts, just somewhat delayed. TPS voltage at 1.15V at idle, 4.30V at WOT. Tach reads properly. No excessive temperature, about 130F at the pan. Let her cool down some, took her out again, same thing - all gears are there, but delayed upshifts, and no lockup in OD. And this is what gets me - my TCS is on a manual switch, it should not care one bit if the PCM has entered in limp mode or not, when I hit the switch it should lock - but no, it would only lock in 3rd, not in OD. Scanned for codes, came up with 62 CM - also odd, since the PCM is fed a dummy signal and it don't see the actual TCS coil voltage drop, ever! Disconnected the batteries, waited, hooked them back up, scanned for codes - all clear. Took her out again, was acting up in the same manner for the first mile, then all of sudden she locked in OD, and shift schedule went back to normal. Drove around for a bit, both at light throttle and foot to the floor, played with the lockup and manual shifting - all is perfect, as if nothing ever happened... Scanned again, and guess what, CM code 62 is back, but the PCM don't seem to care about it at all.
So do ya'll got any ideas as to *** happened? I have a pretty good idea why CM code 62 keeps coming back, I got the gut feeling it never really went away for the last few years, but that the PCM being as old as it is just ignores it - will measure TCS coil resistance tomorrow and swap dummy load resistor to verify this. However, what would cause a full-manual-control converter to refuse lockup in OD only, but still lock in 3rd? And why would the issue go away just as sudden as it appeared?
So do ya'll got any ideas as to *** happened? I have a pretty good idea why CM code 62 keeps coming back, I got the gut feeling it never really went away for the last few years, but that the PCM being as old as it is just ignores it - will measure TCS coil resistance tomorrow and swap dummy load resistor to verify this. However, what would cause a full-manual-control converter to refuse lockup in OD only, but still lock in 3rd? And why would the issue go away just as sudden as it appeared?
