Code P0042 on 2004 envoy

normally if you clear the codes it means that all the codes are cleard, unless there was a problem with the car that was never sorted out, and if that is the case they should be able to tell you what the code means

In my database, that code doesn't compute for your vehicle? With the larger engine, my database says bank 1 and bank 2, sensor 1 and sensor 2. No sensor three. The code does talk about 02 heater circuit, so, I would have to check wiring circuits. Once the problem is fixed, the check engine lite should go out. The code will probably stay in memory for so many engine warm up cycles then it is gone.

My scanner will read and erase codes. You can check some obd2 code readers, see if they will read and erase codes? Some people will take the negative battery cable loose to erase codes. I have to say, I don't like to do that. If the problem isn't fixed, the lite will just come back on, again.

Not heard of a link error code! What was the check engine code number?

What's your check engine code?

I think you mean secondary air pump, see attached figure, it is item #6. There is also a valve involved (item #2). Sometimes water gets into the lines causing fault.

You have a failed transmission, it will need to be torn down and inspected to see exactly what went wrong internally.

A check engine light can be any combination of about 300 codes. Some are simple, like a leaking fuel cap and some get very involved. Without the actual code(s) there is no telling why the light is on.

Our mechanic said we need to replace the computer! The cost will be $1,000.

p0128 engine coolant thermostat below operating temp. Possible low on antifreeze. not plugged in, possible chaffed wires.

P0106 pertains to the throttle body. most cases involve cleaning the throttle body

p0614 i could not find code definition

The knock sensor is for the timing advance on your envoy. It will not be related to your sparkplugs. Your knock sensor will be screwed into the engine block, or under the intake depending on model. The V8 engine is under the intake.