'95 Aurora stays in only in 2nd gear

Dear Members!

I have a nasty problem with the my Aurora and i'm looking for your help. I live in Hungary and i own a '95 beautiful Aurora which is quite uncommon here in Europe and maybe mine is the only one in Hungary.

The whole problem started with a faulty ignition switch which caused several hard stall while moving, shutting down the electrical system completly. After a few stalling the transmission started to fail to shift to OD (or even to D?) and later the only available gear was the 2nd (in failsafe). I bring to car to a local transmission mechanic how exchanged the "A" and "B" solenoids but it didn't help. This mechanic refused to remove the transmission and look inside it due to the lack of lifting equipment. I moved to another mechanic who disassembled the tranny completely but he find nothing unusual. He checked the sensors, valves and the solenoids but all seemed to work well.

The situation now is the following: The car still in 2nd gear only. DTC 86 (undefinied gear ratio) is set after a few miles driving and it stays until swithing the car off. Once I found a DTC 76 history (PCS, pressure control solenoid error) as well. I went through the diagnostics according to the service manual. DTC 86 tree-> resulted possible PCM or EPROM fault, DTC 76 tree resulted possible PCM fault (resistances OK). No other DTCs set.

Soleonids "A" and "B" seems to work well, i hear a "click" when energizing them with the TECH1. The TECH1 has a PCS test too which makes it possible to change the PCS command from low to high. This test seems to fail: when the commanded current is 1A the actual current remains 0A.

Does anyone has any idea what should cause this problem? A faulty PCM or something inside the tranny? Maybe the frequent stalls due to the faulty ignition swith ruined the PCM or a sensor? I'd like to narrow the problem as much as its possible since it takes a lot of money and time to order any part from the USA.

Every bit of advice is greatly appreciated.

Hello from Russia friend !


Sorry to hear all that, but this is nothing scary i rekon.
Your diag tells everything - change PCM and PCS.
95 PCM's are known to fail under some conditions - i replaced mine first day i bought my 95 =) Due 2 unclearable ignition errors and hard idling.
New PCM cured all that immidiately.
It's about 100-150$, look for yours above passenger legs, get part no. and do a search. These pcms are nothing rare.
And also i'd replace... Pressure Control Solenoid..ATP Part # JE7 is only like 40 bucks at rockauto... If you have a manual it's nothing too serious at good service.


I mean first off your electrical stuff may well have fried pcm.
And solenoid aint responding will definitely get your tranny into limp mode.

Cheers
EDIT: Use rockauto.com and choose EMS shipping - it's about 3-4 days !! Ultrafast
EDIT2: I see you claim to checked ALL solenoids ? You sure u checked PCS ? If yes and it works with a battery, but not works with tech1 commands - id say PCM's circuit fried =) AND check wiring !

Lynzoid: thank you for the answer but i'm still sceptic about the PCM. The shop manual states that only ~20% of the errors can be diagnosed using the DTCs and the relevant chart, and this is also my personal experience. Anyway, i'll purchase a PCM since i don't have a better idea. Regarding the PCS, i'll checked its resistance at the PCM connector (should be 3-8 ohm) and it was OK but i didn't test it with a battery. The mechanic told me that he battery tested it and it was OK. I'll test it personally before ordering new parts. I guess i should hear a click from the tranny at least.

BTW, is it possible to remove the side pan without removing the tranny?

PS: it good to know that there are some more Aurora fan around here

Again, check wiring from PCM to PCSolenoid !

When they changed the shift solenoid there should have been an L bracket modification that came with the kit. This L bracket helps hold the screen/filter into place its located b/t the shift solenoids. I change my solenoids and didn’t install the L bracket and the screen would blow out a little bit causing the car to stay in lump model which is second gear only. After installing the L break to keep the screen into place the trans work normal. All you have to do is take the trans pan off to see if the L bracket is on the screen. To install the L bracket I think you have to take the value body off, but not really sure I did it like 3 years ago.

Hmmm. Thanks for the idea. The new PCM is on the way now. If that doesn' t cure the problems, i'll give a try to the bracket as well. Unfortunately i'll have to buy then a new improved "A" and "B" solenoid set because i guess it isn't possible to purchse that bracket separately.

Thank you again.

mate be sure you ordered right pcm! 95s got like 3 possible variations. also you will definitely (!) have to take your old EEPROM chip from your old pcm and put it into new one. They are under covers which are screwed on a pcm's top. under there is self explanatory =)
be ready to get extra DTC first time you start up with new pcm !
It'll definitely will throw 80 - incomplete idle/tps learn, but relax it'll go away after about of hour of driving, may come up up to 3-4 times but will clear without even leaving history code very soon.

cheers
ps. have you multimetered the pcm-tranny harness as i asked ? it may be as i said one faulty wire to PCsolenoid from pcm and you get what you got.
if wires is ok is most probably pcm. as i told, mine first one were throwing 23+25, which by service manual indicated faulty ignition computer (under coils), 400$ part, even after i replaced it - same crap. So i got my part no, got to caddy junkyard and got same one, replaced eeprom and BINGO !!!
I opened old one - no traces (im famillar with circuit boards) of any damage. I traced the 1 contact in pcm connector which was cause of situation. No visible damage there. So i guess that line driver/receiver was fried. BTW GM pcm 95 inside is quite a view =)))

MAKE SURE THE BRACKET WAS INSTALLED OVER SHIFT SOLENOIDS. if it wasnt that is your problem.

I just have received the new PCM and i installed it immediatey. No luck so far. I retried the PCS test with TECH1 again and it it worked when the engine was running. I guess it was OK earlier too, but earlier i checked it with engine stopped. I've checked the wiring earlier to the tranny as lynzoid suggested and it was OK.

After making a short drive-test i've noticed, that if i clear the DTCs then the PCS test with TECH1 is working, but after driving some mile and waiting until the DTC86 is set, then the PCS test fails. The PCS test OK if the DTCs cleared again.

Since i have no better idea, i'll order a new set of upgraded A+B solenoids again i'll install them personnaly. I do not trust in the local mechanics any more.

dfil: did you have any DTCs set when the missing bracket caused 2nd gear only? I mean DTC 86 (undefined gear ratio). It is set all the time for me. The DTC76 (PCS failure) is set only when i try the PCS test after the DTC 86 is set - but it need to be verified again.