Poor Performance When Cold

speedymx · February 10, 2009

Hey guys,

This is my first post here, i hope you guys can help me out.

I just bought a 2000 gmc sierra with the 5.3 in it. The engine light came on so i got it hooked up and it showed codes p0137 and p0157 low volatage o2 sensor #2 bank 1 and 2.

I replaced both sensors and got the code cleared but the engine light came back on. it costs $100 everytime i hook it up so i really dont want to have to do that again. The truck runs very bad when the engine is cold. it will sit and idle fine but as soon as you try to drive it just seems like it has no power and wont take any fuel. it will sputter and bog when you press the gas until the engine warms up more then the problems goes away. The truck runs awesome when its warm.

Any help would be greatly appreciated

Thanks

Draenor · February 10, 2009

When running cold the engine is running in an 'open loop' system. There is no input from the O2 sensors. The ECM is pulling info from tables within itself.

The low voltages could be comming from either, bad connectivity at a connector or a short occuring in the wiring or at the ECM/PCM. Does the DTCs clear when the engine warms up? Try pulling both battery cables for a minute or two. This will reset the ECM.

Go to autozone, the can scan it for free.

speedymx · February 10, 2009

the engine light will shut off after a while if you drive the truck really easy. iut only seems to come on when there is a load put on the engine for a period of time. Where is the pcm/ecm located so i can check the connectors.

speedymx · February 10, 2009

all the connections on the pcm look good, i dont know where to look for shorts in wires because i dont know a lot about stuff like that. any more help would be awesome. it would save me a bunch of money at a dealer

speedymx · February 11, 2009

any other idea on what this could be? the people at the gm dealer dont know whats wrong with it and i dont wanna pay them $90 an hour for nothing

thanks again for the help

DofD · February 11, 2009

Have you changed the fuel filter? The fuel pump may also be having problems. I would suggest having the fuel pressure tested to see if the fuel pump is sending enough fuel.

speedymx · February 12, 2009

ill take a look at the fuel pressure, do you know what it is supposed to be at? and i havent changed the fuel filter, probably be a good idea to change it regardless

Draenor · February 12, 2009

ill take a look at the fuel pressure, do you know what it is supposed to be at? and i havent changed the fuel filter, probably be a good idea to change it regardless

At least 50