Thread: Tranny will not down shift

I have a 1998 GTP. The trans has a ZZP shift kit and a tranny cooler. The transmission started acting up a few days ago. When driving and coming to a complete stop the car is not downshifting. When i try to start going is gets stuck in 2nd or 3rd gear. (verified with DHP) When going up through the gears it shifts very crips & clean. THIS IS ALSO AN INTERMITENT PROBLEM. The only codes that are being thrown are P1676 & P0107 & P0172. One is a bad map sensor and I replaced the male end of it with one from ZZP but the code is still there. Anyways not sure what the other codes mean ill try to look them up.. Also when it is acting up I cannot remove the key. Any ideas whats up. I really think it is an electrical issue but have no clue where to start. Any Ideas?

Ignition switches are very common to go bad in these cars. Your car may be taking off in 3rd gear when this is happening. 3rd gear is what the car will start in if there is no power going to the shift solenoids. Without some schematics there is not much you are going to be able to trace and being intermittant makes it worse. The easiest thing to try is to put a volt meter or test light on the ign power wire going to the trans-power for shift solenoids-and make sure there is power there the whole time you are driving. Normally if the ignition switch is going bad it will happen during a key cycle and not while you are driving but the contacts do go bad and can act up after the car is on for a while and resistance builds up. This can also cause the key problem. Something else to look at is the range switch on the trans. Does the indicator light on the dash show the correct gear when you match it to the shifter? Does the light change or drop out when the problem occurs but is fine otherwise?

The Gear indicator seems to be fine

Coudld this be the Bad Map Sensor?? Does the Map Sensor send and type of electronic signal to the tranny?? Does it convert a electronic vac reading to the tranny? All grounds/ linkage is good. Only thing that comes up on a scan is P1676 & P0107 & P0172

AH HA I swapped out the new MAP sensor and everything is back to normal. When I remove the whole sensor I ended up finding a VAC line attached to the bottom of the MAP sensor. HMM Guess that was the issue. THX GOODNESS just a $50 sensor