P0137 and P0157

I have both of these codes on a 2000 Silverado with a 4.8 engine. I am looking for some advice. I already have preformed the entire fuel pressure check that is outline in the Haynes manual and replaced the Fuel Pressure Regulator, as the pressure was low. However, the code persists after resetting it. I have heard form other sources that the O2 sensors GM used in these trucks are due for replacement after 100,000 miles. Is this true? Also what voltage reading should I be seeing at idle and at wide open throttle from the O2 sensors. I have already checked the connectors for water and corrosion and they look fine.

I have both of these codes on a 2000 Silverado with a 4.8 engine. I am looking for some advice. I already have preformed the entire fuel pressure check that is outline in the Haynes manual and replaced the Fuel Pressure Regulator, as the pressure was low. However, the code persists after resetting it. I have heard form other sources that the O2 sensors GM used in these trucks are due for replacement after 100,000 miles. Is this true? Also what voltage reading should I be seeing at idle and at wide open throttle from the O2 sensors. I have already checked the connectors for water and corrosion and they look fine.

both downstream sensors are reporting a lean condition....what is the fuel pressure ????must be 53-62psi...

did you check for intake leaks....////including any leaks in the air ducting after the MAF????

since both sides of engine are creating the same lean reporting from O2 I would not expect the O2 to be bad...

the manufactures recommend these o2 sensors to be replaced at around 100,ooomi....if you do all hyway longer if its stop and go all day shorter mileage....basicly hours of engine operation will be longer with the given mileage in stop and go traffic..

since this is both sides I don't think exhaust leaks are involved...

obviously any improper crankcase venting [PCV ,hoses etc] will cause this..

as well as fuel filters and air entering the engine intake after the maf ,,,injectors dirty....etc..

Fuel pressure was with in spec and we changed the fuel fillter before we did anything. I am leaning toward dirty injectors right now. Is there a good additive around or is it best to have them cleaned at a shop? Or is it worth trying to pull an injector to see what it looks like?

I'd start by cleaning the MAF (brake or carb/throttle body cleaner wont due as they leave behind deposits) and check for air leaks as suggested above.

In addition, it would seem that in order for the O2 sensors to read lean it would need to be a substantial vacuum leak that you would be able to hear. Am I correct? I would also think it would run extremely rough and have multiple miss fires.

If it's got a MAP sensor check that too.

"In addition, it would seem that in order for the O2 sensors to read lean it would need to be a substantial vacuum leak that you would be able to hear."


You'd think so but not always. The computer is just throwing the code to tell you there's a discrepancy between what it thinks the mix should be and what it is, it's not saying how much it's off by, could be a little could be alot. Without a data logger there's no telling.

Fuel pressure was with in spec and we changed the fuel fillter before we did anything. I am leaning toward dirty injectors right now. Is there a good additive around or is it best to have them cleaned at a shop? Or is it worth trying to pull an injector to see what it looks like?

you do not indicate what pressures you measured...the pressures I stated come from the 2000 OEM repair manual,,

you do not indicate what pressures you measured...the pressures I stated come from the 2000 OEM repair manual,,

The pressure was with in spec. 55 psi.

I am also wondering now if anyone has ever seen a K&N air filler cause this problem. The owner said the filter has been in the truck for about a year and he has never cleaned it and re-oiled it. Is it possible the K&N filter could just be letting to much air in?

I am also wondering now if anyone has ever seen a K&N air filler cause this problem. The owner said the filter has been in the truck for about a year and he has never cleaned it and re-oiled it. Is it possible the K&N filter could just be letting to much air in?

the air filter is before the MAF therefore this would be impossible ...the air entering after the MAF IS ONE area that could cause BOTH o2 sensors to report a lean condition...

my 2000 sil has had the KN filter since 2000...clean every couple of years about 20,ooomi....BUT I don't live in a dust bowl area...

with off roading and large areas of soil blowing this may need a wash and oil more often....with this filter follow the instructions ...do not put a wet filter into the vehicle....

check all vacuum hoses///pcv etc....intake gasket for leaks
use of propane gas directed at the suspect areas will cause a rise in rpm if you hit the leak...