code 42

[Sgyates27253]

code 42..just finished redoing dash..bezel lights,tach gauge,and some soldering on the printed circuit..and a new radio..not sure if something went wrong there?? everything fine for first 25mile then code throwed.reset... then about 150 miles code thrown again..researching now ..any advise greatly appreciated

 

[dyeager535]

In my signature is a link to a page with all the service and parts manuals. Download the ones for your truck. Make sure they are R/V series manuals for '87-91 trucks though, I found at least one that the new-body style C/K manual was mixed up in.

Diagnosis/troubleshooting should be the same for all years, but it's never a bad idea to get the right manual, when it's available. The service manual (or emissions manual, if used that year) should have the code descriptions and troubleshooting flow charts.

Just remember, the code does not mean X component is bad. It means the ECM is not getting the expected input from a particular circuit. Could be a bad wire, a bad connection, another component providing the ECM incorrect input, etc. Thus the flow charts.

 

[dyeager535]

In my signature is a link to a page with all the service and parts manuals. Download the ones for your truck. Make sure they are R/V series manuals for '87-91 trucks though, I found at least one that the new-body style C/K manual was mixed up in.

Diagnosis/troubleshooting should be the same for all years, but it's never a bad idea to get the right manual, when it's available. The service manual (or emissions manual, if used that year) should have the code descriptions and troubleshooting flow charts.

Just remember, the code does not mean X component is bad. It means the ECM is not getting the expected input from a particular circuit. Could be a bad wire, a bad connection, another component providing the ECM incorrect input, etc. Thus the flow charts.

 

[rndmerrill]

In my signature is a link to a page with all the service and parts manuals. Download the ones for your truck. Make sure they are R/V series manuals for '87-91 trucks though, I found at least one that the new-body style C/K manual was mixed up in.

Diagnosis/troubleshooting should be the same for all years, but it's never a bad idea to get the right manual, when it's available. The service manual (or emissions manual, if used that year) should have the code descriptions and troubleshooting flow charts.

Just remember, the code does not mean X component is bad. It means the ECM is not getting the expected input from a particular circuit. Could be a bad wire, a bad connection, another component providing the ECM incorrect input, etc. Thus the flow charts.

Thanks for the manuals.. I downloaded the 1991 emissions and driveability manual.. I didn't see one for the 1990.. Do you think any of the information will be different?

 

[Wes Harden]

probably not not a lot of change for the early nineties.

 

[dyeager535]

Between those two years they are probably identical. I'd never assume though, at this age someone else could have been in there messing things up, and/or the wire color for that circuit could have changed. GM did ridiculous things sometimes.

I'll always use a multimeter on whatever wires I'm dealing with to make sure what I think they are, is really what they are.