97 Chevy S10 ODB Codes 420, 171, 174 is fixed how?

Question

I have a 1997 Chevrolet S10.

I receive ODB II codes

PO420 Catalyst System Efficiency Below Threshold (Bank 1)
PO171 System too Lean (Bank 1)
PO174 System too Lean (Bank 2)

How can I fix this problem?

Thank you for your responses!

I had already replaced the fuel and air filter. I will replace to O2 sensor tho..

Answer 1

Not familiar with GM products but I can tell you that P0171 & P0174 indicate that you have a vacuum leak of some sort that affects both banks. I would approach this by locating the source of, and repairing the vacuum leak FIRST, BEFORE "throwing parts at it" in hopes of fixing it. You'll be wasting unecessary money by doing so. You can locate the source of a vacuum leak by administering propane from a bottle with a rubber hose attached with the engine running. When you hear the engine RPM increase, that's where your vacuum leak is. Possible sources are a cracked PCV hose, upper to lower intake gaskets, any hose or tube disconnected from the air inlet tube. You should be able to hear a "hissing" sound from the area of the leak. Hope this helps.

Answer 2

There are two different issues here.
The first two codes refer to the fuel trim and control. The second issue is the cat monitor. The catalytic converter isn't a computer component. But the law requires that it be monitored by the PCM. This is done by an oxygen sensor after the cat.
With all this in mind, there are a couple of ways to go about this.
1) Replace all the oxygen sensors, clear the codes and HOPE that was the problem.
2) Perform proper diagnostics.
If you are unfamiliar with the strategy or the technology of the PCM and its monitoring arrangements, save a lot of money, time, effort, a few swear words, and bunches of frustration and take the little trucklett to a licensed SMOG repair shop and ask that the diagnostics be performed. Repairs can be done afterwords.
It is possible to replace the sensors, and find out later that the sensors were accurate, and that there is a fuel delivery issue or a fuel management issue, and the sensors have identified it.
It is possible also that the cat is fine, or that it has been contaminated by (?) and is no longer operating at optimum levels, and again the sensor has found the problem.

Good Luck and Merry Christmas

Answer 3

Change the fuel filter, and air filter. The fuel filter because your injectors may be running at minimum pressure and you are actually running lean,

The air filter because a dirty air filter will restict the air flow. The computor will try to reduce the fuel to match the air. Once it can't go any lower it will throw the po171&174 codes, which are the same codes for lean system(why they use the same code is beyond me).

The po420 is from a o2 sensor behind the catalytic converter(I'm guessing it is a single ehaust system hence only one code?). It's detecting a problem ahead od it. Change those two fillters and all 3 codes should go away.

hth

Answer 4

1. Take S10
2. Drive Off Cliff
3. Live Happily After That

Answer 5

just an idea not one that can be cheaply done but maybe the egr valve is bad or the mass air flow sensor.