Gmc Sierra 4.3l 1988 Pick-up [diag Code 45] Help!

[kbelanger]

We have an old GMC Sierra 4.3L 1988 Pick-up here at the farm.

 

The truck is in good condition but for some time when we start it the sound is irregular and after a certain period of time at idle speed the “Service engine soon” light goes ON.

 

Then the truck stalls if we try to move it.

 

The diagnostic code is 45

 

Here is what I found for code 45:

 

Oxygen sensor or circuit - rich exhaust detected

 

Oxygen sensor voltage was over 0.7 volts for 30 seconds after engine had been running for 1 minute with a throttle angle between 2% and 20%.

 

Now I want to know what I should check, do I need to change the O2 sensor? Do I need to check something else? What is the debugging process of this kind of problem?

 

Thanks for your help,

 

Keven