SJ75

How many o2 sensors are there. And where are they located? I can find two by the transmission. I just want to make sure there aren’t any I am missing. 2003 2500HD Sierra v8 gas Shane

@Formulabruce. So where is a good place to get these parts from.? Along with a good instruction manual on how to do it. Unless by some miracle I find a shop that listens and wants to help, I am looking at doing this on my own. I am mechanically inclined.

Tires I dont think play a roll here. News ones put on in decemeber with the problem going back a couple years. I never got any letter from GM about an upgrade to solve problems in the 4L80E. Then again the dealers around here dont want to do anything. So finding a reputable place around here is a shot in the dark. Since I am not hearing or feeling anything, I will start with the solenoid. And look at the rest when I have the money. I will do the ground check as well. When All this throttle body code started that cold 10 degree january morning 4 years ago, it went to a place where I think they did more damage then good. That place is gone and nobody knows where the guy went.

The update info ; Now that this project has me doing almost all highway except the last mile two new clues have emerged. two points on the high will most likely trigger the Flashing CEL. going over 60 on shallow long down grades where light power has to be applied to keep speed up. steeper down grades backing off throttle completely doesnt do it. up hill under power nothing. flat runs only if the run is long and it gets over 60. The other clue since it sat for a while because of work stoppage, Iet it sit for two weeks or more and just turning the electrical system on will trip the reduced power. Start it up and it still responds to throttle inputs in park, let it warm up, shut it down and restart and the reduced engine power disappears. the cel stays on for a while. it too clears on the next start. possible suspects? MAF? IAT? Gasket? Crankshaft sensor? Original: I have a 2500HD, 2003, 202000 miles 6 liter gas. So I have been battling the dreaded throttle body code. It comes with 0300, 0600 codes. Replaced the throttlebody, fuel pump, plugs, plug wires, coils, and computer. Here is what it is doing right now. At idle it has noticeable misfires. Under power it doesnt misfire. If I run over 60, the check engine flashes for 3-5 seconds. then goes out. It will only do it if I run for at least a minute or more over 60. No sounds, or vibrations, gauge indications, that indicate any issue. if I keep going. It can take a while for it to cycle like that again. Below 60, I can go and nothing shows. No check engine light. Also cold days if I dont let it warm up it can trigger the reduced power mode if I move it above 50. But once warm it is fine. It does restart with no issue. Oil level does not change over the life of the oil, no visible exterior fluid leaks. The mechanics around here just like to check the codes and and say it is the throttlebody when that has been replaced 3 times. (I kept the last one). They dont seam to want to do anything past that. Also, It doesnt like staying in over drive. it shifts out sometimes. Sometimes it stays. Dont think it is the clutch. it shifts smooth and quiet in all gears. Most of the time I only know it shifts by watching the RPM's I am thinking solenoid is going bad. Thoughts? This engine and transmission have never been opened. there has never been a need to get inside either. only the valve covers removed to inspect for a possible issue that might be cause a misfire.