Some error codes that I would like to get cleared up.

[emedlin]

04 Envoy XUV w/ inline 6 seems to to run fine and has 127K miles on it. The check engine light came on and I got Advance to read the codes for me. A few days later the light went off. Maybe a week after that the light came on again. I used my code reader that I just got and here are the codes I got this time. I am 90% sure they are the same as before.

P0128 - Thermostat needs to be replaced, but I haven't noticed the temp gauge being low. I will ask my wife to keep an eye on it.
P0606 - PCM/ECM fault. I had this way back in 08, and I would get a stall and reduced engine power with it. It only happened once or twice back then and never again. Now it runs fine, so why the code?
P1680 - Reprogram or Replace PCM. Really, another PCM error. Maybe APP sensor. PCM probably has the original firmware or atleast something from late 05 when we bought it used. May need to be flashed to something newer.
P0526 - Cooling fan. I have heard it roar like a jet a few times before, but that was maybe a year ago. Nothing recently. Was going to replace it when it roared more consistently.

I am going to assume P0128 is the thermostat as it is the original one. For the other three could they all be related to a short in the fan clutch? Could the short be briefly enough that the fan does not spin up to jet engine speed before the PCM can read it again and pulls it back down? Would like to get efans from pcm4less. But, a new clutch is cheaper.

 

[eXplicit]

04 Envoy XUV w/ inline 6 seems to to run fine and has 127K miles on it. The check engine light came on and I got Advance to read the codes for me. A few days later the light went off. Maybe a week after that the light came on again. I used my code reader that I just got and here are the codes I got this time. I am 90% sure they are the same as before.

P0128 - Thermostat needs to be replaced, but I haven't noticed the temp gauge being low. I will ask my wife to keep an eye on it.
P0606 - PCM/ECM fault. I had this way back in 08, and I would get a stall and reduced engine power with it. It only happened once or twice back then and never again. Now it runs fine, so why the code?
P1680 - Reprogram or Replace PCM. Really, another PCM error. Maybe APP sensor. PCM probably has the original firmware or atleast something from late 05 when we bought it used. May need to be flashed to something newer.
P0526 - Cooling fan. I have heard it roar like a jet a few times before, but that was maybe a year ago. Nothing recently. Was going to replace it when it roared more consistently.

I am going to assume P0128 is the thermostat as it is the original one. For the other three could they all be related to a short in the fan clutch? Could the short be briefly enough that the fan does not spin up to jet engine speed before the PCM can read it again and pulls it back down? Would like to get efans from pcm4less. But, a new clutch is cheaper.

The P0128 code could be connected with the P0526 code you've gotten, considering they're both related to the cooling system. I guess the fact that there's only 2 cooling system codes, process of elimination wouldn't be that expensive.

I just had to deal with a problem where I was getting a P1221, P1516, and P0507. All because of the little hose that ran from the bottom of the intake manifold to the crank case. 6 inches of hose that I ended up not using the factory molded rubber hose. Replaced it last night and it's been running great all morning. Much better than it was before.

 

[IllogicTC]

On P0128: The temperature gauge lies. If your scan tool has live data capability, you can get a much more accurate number. That thing literally sits in 210 from like 190 actual degrees up to at least 207, and probably includes 210 but you never know.

Also, there's more than two cooling codes possible. 117,119,125

It's likely that the thermostat has failed in the open position (seems to be the more common failure position, luckily). While this can slow down engine warm-up time, once it's been driven a little it'll be up to proper temperature (according to the gauge) anyway. While it won't starve your engine of much-needed cooling, it can affect other things like leading to extra carbon buildup as the engine may not be truly reaching proper operating temperature (remember, the gauge tends to lie though not a total fabrication like the oil gauge).