2000 GMC Sierra Trouble Codes

Can you put a scanner on it, that shows live engine data and freeze frame data. The freeze frame data might show you what was happening when the codes set. Intermittent egr or vacuum leak if it isn't an injector issue/fuel issue.

Yes I have a scanner with a freeze frame. Hate to have it connected all the time but I'll just have to do it. Just never know when the code is going to trip. I forgot to mention that I cleaned the PCV valve as well at the last reset. Motor is very smooth all the time. Can't find any vacuum leaks externally. Any clues where to look for one? I have been loosing coolant (about a quart a week) and am beginning to think that I may have an intake leaking near a coolant port. I can't find any coolant on the ground or under the hood. No contamination in the oil either. Any one seen or heard of the intakes leaking on these motors (5.3L)? That would explain the lean bank and its both sides!

I believe the freeze frame data is stored in the computer memory, just like the codes. You shouldn't need the scanner hooked-up all the time. When you erase codes, it may also erase the freeze frame data.

OK, thanks. Didn't know that. I will wait for light then try to get to the freeze frame data. I use a ACTRON 9180 Scanner. I will try and get the freeze frame data from the computer using this scanner once I get the light again. Will keep you posted.

Any clues on the coolant?

I just hooked up the scanner and checked for freeze frame data and no freeze frame data present...

Does your radiator have composite end tanks? I did see a bulletin about the filler neck sealing area having imperfections. I don't know if that is your problem, it could be several things.

OK thanks for the tip. The radiator does have composite sides. I have looked up and down both sides and cannot find any fluid. That is what's so frustrating. I can't find any fluid anywhere. I thought I found it when the composite connector at the heater core (white one) poped off when I was removing the EGR valve. Installed a new one and still am loosing fluid. I'll keep looking. Had to add about a 1/3 of a gallon this morning. Got "low coolant" light yesterday on the way home from work.

Does the oil look ok? If the leak isn't external, it may be internal. I'm not aware of any gasket problems on this vehicle, the bulletins didn't show anything. I don't know if a leak detection dye would help or not?

No fluid in oil. Change the oil regurlarly. Starting to think that have a leaky heater core. However the fluid that comes out is clear, never green.

Common problem regarding loosing coolant:
Leaking coolant pump throws out fluid, finding the leak is not obvious because it only leaks when going down the highway or higher engine speeds.

Check it out, you never know.

I have replaced the water pump. Think leak is internal. Cracked head or bad intake gasket, or bad head gasket.

It's possible.