check engine light no codes hard shift

[ftmfg]

hi, hoping someone can help me with this. I have an inteminent check engine light that does not trigger any codes. when the check engine light is on the auto. trans. shifts very hard. that appears to be the only symptom.
thanks

[badazzstroker]

if the light came on then you threw a code of some sort.what are you scanning it with not all scanners will pull all the codes on a stroker.

[ftmfg]

its a small hand held unit that they use at autozone

[badazzstroker]

yea,that unit will not pull our codes especially tranny codes and that sounds to me what you are going to throw.

[ftmfg]

OK, thanks will try a more sophisticated tester

[ricksstang]

My 95 f-350 w E4OD did the same thing. the tester @ autozone and advance auto would not pull any codes. Had to use a Snap-On code reader to get the code.
Mine was a P1728, which is slipage in the 3/4 clutch pack. Could be Lock Up in the convertor or could that the trans is slipping in third or forth gear. Mine was the latter. Good Luck.

Rick

[ftmfg]

hey rick, thanks for the reply. what did you do to fix the problem? right now on my truck when the check engine light comes on the trans. shifts gears almost violently, depending on the RPM's and then shifts normal when the check engine light goes off. i just brought it to a shop that has very good techs and equipment and they where unable to come up with any codes that seemed to be related to the hard shift problem. any suggestions ?
thanks

[nm50]

mine does this occasionally. it is the torque converter locking up. it won't unlock during shifts making for a very hard shift, and it locks way to early making it feel like a manual. my superchips tuner says it is a throttle switch. that means it is either the idle validation switch or the throttle position switch. worst case is you have to replace the pedal assembly which gives you both switches for about $200 (Ford Parts and Ford Diesel Parts at Powerstroke Shop). easy solution is to clean the terminals on both switches with some good contact cleaner / oxidation remover.

[ftmfg]

cool, thank you very much for the info.

[ftmfg]

thanks again, checked and cleaned connections. initial results are promising. wish I had waited a while before dropping $170. at the shop where they couldn't even diagnosis the problem.