Our 2004 Envoy has had the engine light on since last night. It is a code PO128. We have plenty of antifreeze, and it's not overheating. We are getting some heat through the vents, but not really hot. Any ideas? And is it OK to drive like this a couple days before we can get to the mechanic?
This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostate if its not overheating get it to a mechanic its probly stuck open
SOURCE: check engine light going on and off the last
Where is the Engine Coolant Sensor located on my 2002 Envoy?
SOURCE: 2004 GMC Envoy.Check engine soon
This code indeed does indicate a bad thermostat, but not in a way as overheating but the coolant temperature is not rising fast enough at warm up because the stat is always in the open position.
The rushing air sound you heard was most likely the electronic fan clutch starting to go bad. This is a common problem.
SOURCE: 2003 GMC Envoy Service Engine light on. OBD2 Code
Ah the famous P0128.....It's 1 of 2 things. If your fan is not engaged constantly (would sound like an airplane or big rig everytime you step on the gas) and is working properly, that rules out the fan clutch. The other common problem is the thermostat. Replace the thermostat and the code will go away. Engine temperature needs to be at 210 degrees on these engines. If the fan clutch is constantly engaged, it's cooling the engine off constantly and won't get up to 210 fast enough. If it's the thermostat, it's stuck open and isn't allowing the coolant to properly heat up in time.
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And, the temp is reading what it should, right in the middle of the gage.
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