1996 Plymouth Voyager STALLING

HELLO!VAN WAS STALLING, HARD TO START AND CHECK ENGINE LIGHT ON. TOOK TO MY MECHANIC, AND HE SAID IT WAS IDLE AIR CONTROL WIRE HAS BATTERY VOLTAGE(IDAC, 1 WIRE HAD 12 VOLTS). TOOK TO DEALER, THEY CLAIMED NO CODE, BUT THAT I NEEDED THROTTLE BODY AND FUEL INJECTION CLEANING AND NEW BATTERY (DEAD CELL).I PURCHASED BATTERY AND THEY PUT IN AND "SUPPOSEDLY" DID CLEANING. CHECK ENGINE LIGHT WAS OFF WHEN I PICKED IT UP, BUT NEXT DAY AFTER WORK, (I WORK 3 MILES FROM THE DEALER) HARD TO START AGAIN AND CHECK ENGINE LIGHT BACK ON. WENT TO AUTOZONE AND HAD THEM DO TEST AND CODE CAME BACK "O0505 -IDLE AIR CONTROL VALVE CONTROL CIRCUIT"WENT BACK TO DEALER AND HE SAID THAT THEY DID NOT HAVE ANY CODES WHEN THEY RAN DIAGNOSTIC, THAT THE DEAD CELL IN BATTERY ERASED CODE. FROM TIME I BROUGHT TO MY MECHANIC THEN TO THE DEALER WAS ONLY A COUPLE OF HOURS, HOW COULD THE CODE DISAPPEAR WHEN THE CAR WAS STARTING UP. MY QUESTION IS CAN DEAD CELL ERASE CODES?DID I GET THE ROYAL RIP OFF PAYING FOR THE THROTTLE BODY AND FUEL INJECTION CLEANING?I THINK THEY JUST DID THE CLEANINGS FOR THE MONEY AND KNEW THAT I WOULD HAVE TO COME BACK BECAUSE THE CODE WAS STILL THERE, NO MATTER WHAT THEY CLAIM.
ANY INPUT WOULD BE GREATLY APPRECIATED.
THANKS!