I HAD THAT CODE TOO HAD VACUUM LEAK BEHIND MASTER CLY THE FRONT BRAKE BOOSTER SEAL WAS TORN REPLACE SEAL TOOK CABLE OFF BATT IT WENT AWAY.CODE PO 171 VACUUM LINE ,MAF PO 171 SYSTEM TOO LEAN (BANK 1). HAD BOOSTER TROUBLE REPLACE SEAL BOOSTER OK DID NOT HAVE TO REPACE BOOSTER WAS VACUUM LEAK BRAKE BOOSTER FRONT SEAL HAD TO PICK UP AT JUNK YARD NO ONE HAD IT IN AUTO STORE OR DEALER CHECK OBD-II Trouble Codes - DTC Codes Car Repair