1997 Cadillac SLS

Computer problem
1997 Cadillac SLS V8 Two Wheel Drive Automatic 109000 miles

obd2 scanner brings up po171andpo174saying the car is running lean.I check fuel injectors for leaking and clogged they seem to be o.K. If it is a oxygen sensor gone bad I have three how will be able to tell which one is the problem. Thanks for helping.
October 17, 2009.

Check vacuum hoses for splits, kinks and proper routing. Check throttle body, air induction system after MAF sensor, intake manifold, PCV and EGR valve for vacuum leaks. Check for contaminated fuel. Ensure PCM grounds are lean and tight. Check for mechanical failure. Repair as necessary

Oct 17, 2009.
I did what BMRFIXIT and the forum said to do, but my results were the same. The check engine light is still on. What do I do now?

Oct 19, 2009.
I obtained this TSB and will share it with you hope it will help let me know

Affected Model(s): 2006 and Prior All General Motors Passenger Cars and Trucks; 2003-2006 HUMMER H2; 2006 HUMMER H3
Supercedes: This bulletin is being revised to add models and model years and update the name and part number of GM Fuel System Treatment. Please discard Corporate Bulletin Number 04-06-04-051A (Section 06 - Engine/Propulsion System).

Related Ref Number(s): 04-06-04-051, 04-06-04-051A, 04-06-04-051B
General Motors is aware that some companies are marketing tools, equipment and programs to support fuel injector cleaning as a preventative maintenance procedure. General Motors does not endorse, support or acknowledge the need for fuel injector cleaning as a preventative maintenance procedure. Fuel injector cleaning is approved only when performed as directed by a published GM driveability or DTC diagnostic service procedure.
Due to variation in fuel quality in different areas of the country, the only preventative maintenance currently endorsed by GM regarding its gasoline engine fuel systems is the addition of GM Fuel System Treatment PLUS, P/N 88861011 (for U.S. ACDelco , use P/N 88861013) (in Canada, P/N 88861012), added to a tank of fuel at each oil change. Refer to Corporate Bulletin Number 03-06-04-030G, VARIOUS DRIVEABILITY SYMPTOMS DUE TO CLOGGED FUEL INJECTORS, MIL/SES DTCS P0171, P0172, P0174, P0300, P1174, P1175 for proper cleaning instructions.

Oct 19, 2009.
If both banks are setting lean codes, and the fuel trim values are indicating lean, it has to be an air leak that is centrally located. Some possibilities include the vacuum source line for the HVAC at the right of the intake(belt end of engine), there is also a relief valve with a spring loaded door on that end that releases pressure during backfire. The mass airflow sensor could also be faulty and indicating more air than is actually entering engine. There could be an air leak after the mass airflow sensor resulting in unmetered air. The chance that your injectors are equally restricting flow to result in lean conditions are minimal. The fuel pressure could be low, I would think you would have other problems as well.

Oct 20, 2009.
GStacey and BMRFIXIT: Thanks a million for your info on how to fix my problem! It's been 2 months that I have been trying to fix it and you saved me! It was right you said it was by the HVAC replace vaccuum lines which cost 2 dollars. You guys saved me a diagnostic cost as well. Thanks again!


Nov 3, 2009.
Thank you for updating your post with the fix
and very glade you got the problem fix

we are here if need us again
happy driving be safe

Nov 4, 2009.