Chevrolet Repair: Service Engine Soon problem, chevy lumina apv, 1995 chevy lumina

Question
1995 Chevy Lumina APV (minivan), 3.8 V-6, 147000 miles, owned since 115000 miles, no known previous problems or repairs related to this situation.  About 800 miles ago, "Service Engine Soon" light started coming on intermittantly, and vehicle would shift out of or not go into 4th gear, and no torque converter lock up.  Also, cruise control would not function.  Within 200 miles the light stayed on permanently as it is now, with same results.  Engine starts and runs great as it always has, except for OCCASIONAL stumbling or dying at low speed, such as shifting from Drive to Reverse or R to D.  I have tried to clear diagnostic trouble codes as instructed in manuals by pulling ECU fuse under hood at positive battery cable pigtail and in fuse block in glove box, one at a time and both at once, and it has no effect.  If I disconnect battery ground, trouble codes clear.  However, all codes reset instantly if ignition is just turned on (engine off), and Service Engine light is back on within 2 or 3 seconds if engine is started.  Hitting "Clear codes" on the scanner simply makes the light flicker off for an instant with the engine running, and has no effect with key on engine off.  Codes that show on scanner are: 112, 113, 117, 118, 122, 123, 134, 137, 138, 140, 321, 341, 502, 571, 629, 630.  I notice 341 (camshaft position sensor) is one of only a few that would turn the light on. Also, as sort of an afterthought, the remote door lock/unlock recently quit working.  Possibly related? Thank you for any assistance you can provide.

Answer
Hi Roger... if scan toll does not remove codes then they are hard faults... you need to address these and correct them. the computer will not clear any code as long as the problem is still present.first i would check all computer connections for corrosion, as a lot of the times it is simply a bad connection causing the fault. also check and clean all grounds. if that does not get rid of some of the codes then you will need to address these. the scan tool should be able to point you in the right direction as too repair....hope this helps