Code 42

[Brad Bartilson]

My ECM recorded a Code 42 error. Tlink reference
states that the under EST condition, the ECM applies
5V to the Bypass line and expects voltage variations
on the EST line. My Helm's manual states the EST line
should show <1V while idling.

I monitored the Bypass line, saw 4.65 V steady. The EST line varied from 0.6V-1.5V while idling, and up to 3.0V (under acceleration). Most recently, the ECM didn't show code 42, but Tlink was showing continuous Code 42. Is the EST out of range (idling or under accel/cruise)?

-Brad 87TR

 

[gofstbuick]

Have you cleared the code to see if it reoccurs? that is the first step in the trouble tree. If it is intermittent, you sould probably look for poor connections first.