CEL came on yesterday, 2006 ODB trouble codes

[2006Tahoe2WD]

I ended up ordering this one.

 

[2006Tahoe2WD]

For those still here. I have massive good news. The EVAP status finally cleared after not much driving. Right now - I/M status clear and no codes except the HVAC air/fresh air actuator is not happy with a P code. I'm working on that along with engine coolant temp. hot reading steady or correctly.

 

[Mudsport96]

On the cutting the floor topic. I did that on my old 2 door S-Blazer, as dropping the tank on it was a pain with the aftermarket( see homemade) skid plates. But I did go to the junkyard and cut a larger patch piece to put over the hole. It actually overlapped each side by a good 2 inches. Would not do to my current Tahoe as it is still virtually rust free. But 10 years from now, all bets are off lol

 

[2006Tahoe2WD]

On the cutting the floor topic. I did that on my old 2 door S-Blazer, as dropping the tank on it was a pain with the aftermarket( see homemade) skid plates. But I did go to the junkyard and cut a larger patch piece to put over the hole. It actually overlapped each side by a good 2 inches. Would not do to my current Tahoe as it is still virtually rust free. But 10 years from now, all bets are off lol

I probably won't consider cutting the floor but it is tempting. Consider the downsides of dropping the tank down compared to a cut in the floor.

 

[2006Tahoe2WD]

Water temp. sensors. I think I have two sensors. They should read (ohms) similar as the engine warms up or at least track each other. This might confirm that it is not the fault of the sensor for the gauge. I did see mentioned somewhere that the connection via the treads on the gauge can get corroded and provide false resistance readings.

 

[Fless]

I'd find it hard to believe that there are to ECT sensors. Where would the second one be located?

 

[2006Tahoe2WD]

I saw mentioned in a couple places that there were 2. One drives the gauge and the other ? goes to the ECU. I thought it was odd also. I looked this morning but not very well. I did see the one on the front of the drivers-side head.
I did fill the overflow tank a bit about an inch above the "joint" to see if something will change. I don't see the "line" that is supposed to be the cold-fill line so I filled until I could read cold-fill easily.

I'd find it hard to believe that there are to ECT sensors. Where would the second one be located?

 

[Fless]

On mine the cold fill line is the seam between the two halves of the surge tank. "Full Cold" is molded into the upper half, with an arrow pointing down to the seam.

My owner's manual conflicts and shows a line about 3/4" below the seam, marked Full Cold.

Either one should be fine as long as you use the same one for reference, especially when you are monitoring suspected coolant loss.

 

[2006Tahoe2WD]

Yesterday I added coolant to about 1" above the seam when the engine was hot and heater settings were on max. Today the temp. is rock steady at about 195F. I need to test it on a longer drive with some downhill sections. That would be good if adding coolant fixed the issue. A bit embarrassing but still good.

 

[2006Tahoe2WD]

I went on a drive (over highway 17 and back) and the temp. stayed steady. The temp. did drop a bit on 5-6 mile downhill but not much. I think filling and burping the cooling system did the trick. If that's it - the easiest fix I've ever completed. At this point the DIY gods owed me that.

No new codes are showing up. However, I do see my long term fuel trims are at +9% during idle. I don't think the fuel filter or fuel pump has ever been changed (180k miles). I'm considering doing a fuel pressure test to start with. Also I plan to rig up my scanner with long and short trims showing and drive around to see if the engine goes lean requiring more positive trim.