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Dan, Technician
Category: Cadillac
Satisfied Customers: 24007
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Same seldom used 01 DeVille now 53,000 miles, Has 171 and

Customer Question

Same seldom used 01 DeVille now 53,000 miles, Has 171 and 174 codes, lean mixture both banks. Cleared codes went 14 miles and light came back on 171, 174 codes. Put in 2 containers of injector cleaner , went 30 miles for pollution test , no light but was
rejected ( not failed). They told me I need about 7 days use before testing ??? Lite went on after test. I always thought you needed 30 or 40 miles to set the computer. Today went 96 miles non stop on expressway, no light. Stopped for gas and light went on
again when started !! Both codes came on at the same time which makes me think that it is not the sensors. I had cleaned the throttle body and idle valve with carb cleaner recently. I cannot locate the rear bank co2 sensor. What is the most likely cause ?
Thank You Art***@******.***
Submitted: 2 years ago.
Category: Cadillac
Expert:  Dan replied 2 years ago.
What codes are you getting?
Customer: replied 2 years ago.
As stated twice in my letter: P 0171 and P 0174,
Front bank lean and rear bank lean.Art
Expert:  Dan replied 2 years ago.
Sorry about that, how does vehicle run? Does it lack power or idle rough? Thanks.
Customer: replied 2 years ago.
Has full power, Has a slightly rough idle.
Did have a big problem dying at stops recently.
Used carb cleaner on throttle and Idle system and it really helped.
Only driven 7000 miles in last 4 years.
Tested it 96 miles non-stop, no light but turned engine off and restarted and the light came on.
Expert:  Dan replied 2 years ago.
The most common case is a leak in the rubber intake boot that goes between engine and mass airflow sensor so make sure to check that good. Then you can use starting fluid to spray around boot, intake gasket, throttle body gasket, and vacuum lines to try and find leak. Let me know how it goes or if you run into more questions, thanks!
Customer: replied 2 years ago.
I like your answer but I removed and replaced the boot, it looks like new.
I sprayed everything in sight without removing any covers, to no effect.
Drove 65 miles today with no light, went trough the testing lane again today and was rejected { not failed } because they told me I had to use the car for 7 days before testing. I always thought it required about 40 miles.
Check engine light went on again when I left the testing lane.
No improvement, Any more ideas ?
Thanks for your help.
Expert:  Dan replied 2 years ago.
Do the two codes always set together or does one come first?