No Third in D but in D4

[94LuminaZ34]

I'm still trying to figure out my TCC lockup problem and got it narrowed down to a internal tranny problem or the pcm. But I just realized that when I shift into D I have first and second but it doesent want to shift into third? It should shift at 35mph but I can go way past that and it just stays in second with no codes? Any ideas?

[WrathOfSocrus]

If your trans wont lock up the tcc in OD and only goes to second in D I would say the linkage needs to be adjusted. The is an electric switch on the trans that tells the computer what gear you are in. If the linkage is out of adjustment then you can have the trans engaged in the OD gear but the electric switch might not be fully engaged into the selection that tells the computer you are in fact in OD. Then when you shift the gear selector to D the linkage is so far out of adjustment that the trans engages 2 instead of D.

I could be wrong but it seems easier to check that out before replacing the trans or the computer.

[94LuminaZ34]

My scanner shows that I'm in the D position but the tranny wont shift into third also when I'm in D4 the ecm engauges lockup and then turns it off then 10 seconds later the trans defaults to second gear?

[WrathOfSocrus]

Like I said I could be wrong, Dunno what to tell you there. So you're saying in overdrive it goes from 4th unlocked to 4th locked then drops back to 3rd?

[94LuminaZ34]

I explane it better in my other post

http://60degreev6.com/forum/f103/overdrive-problem-t41952

[94LuminaZ34]

OK I got it narrowed down to the computer. I checked all the resistences and made sure nothing was shorted to ground and after I got my hands on a mastertech scantool I determined that the problem is with the computer. I unhooked the transmission connector and hooked up a testlight and then commanded on the TCC solenoid the light will light and then go off and then light and go off every four seconds it wont stay on like it is supposed to and the pwm wiring is also lighting up when I havent even commanded it on and its not shorted. So I bought a used pcm off of ebay and of course it wont work in my Z34 because it is meant for one with passkey and mine is not equiped so I swaped the prom chips and the car ran but had the same problem so I think I have a problem with the prom. Could this be possible?

[gpse3400]

Well not for nothing the transmission will default to 3rd gear. A and B soleniods deactivated is 3rd gear. So thats a nice little test.. But if you have you TCC flipping on and off. I'm thinking and internal failure with the wiring or better yet the solinniod itself.

[94LuminaZ34]

I checked the solenoids and wiring no shorts and no high resistance and the solenoids dont have high amp draw. For some reason the PCM wont keep the TCC solenoid engaged it turns it on then right back off. It does this even when using a scantool and having the transmission unhooked and using a test light the PCM will turn the light on and then off when I command it to be on. I think it might be the memcal so I going to try a different one. If that doesent work I might wire ithe TCC to a switch. I also found that my modulator is shot when I unhooked the vacuum line and turned the modulator upside down it puked tranny fluid so I need a new one but I dont think that would cause the problems I'm having.

[gpse3400]

Even though electrically it might check out, it might not be right mechanically. Even hearing it click is not a good enough test either. It would be best to manually command the soleniod while in motion. If the transmission repsonds then you can rule the transmission out.