EVAP

JAKWLLMW

MEMBER
2007 CADILLAC DEVILLE DTS
194,000 MILES

Started out with code p0411, replaced parts got different codes after each replacement last codes were 0411, 0171 and 0174. Brake booster was leaking badly so mechanic replaced and cleared codes, after thirty miles engine light and driving symptoms came back including smoke under hood.
Previously changed in order, EGR, purge valve, secondary air injection check valve, and vent vac. Each time engine light and driving symptoms came back after twenty to thirty miles of driving. Out my wit's and money.

1 Reply

JIS001

MECHANIC
3,411 POSTS

P0411 is for a fault in the air injection system. The air pump needs to be checked to make sure it comes on and you have a strong air flow. All the hoses need to be checked to make sure nothing is broken or restricted. Check that the air fuse is good and relay operates.

P0171 and P0174 is for both banks running lean. You would need to smoke test the intake system for leaks. Also, have the mechanic look at freeze frame data to see when the lean codes posted. If it posted at idle then you do have a vacuum leak or low fuel pressure. If while at cruise then clean the throttle body and make sure he resets the fuel trim back to zero.

If cleaning the throttle does not help then I would have him check for a faulty mass air flow sensor. If the sensor is faulty I strongly recommend you order an A/C Delco part. Good luck and keep us posted.