Code 42 in a 1993 Regal

I’ve had a ‘service engine soon’ light on for a while now. A friend who used to own a shop showed me how to read the OBD1 code. He read it and used a list at Advance to check the code and he said it was an O2 sensor.

In the meantime, I Googled the code and read that it was involving the EST circuit being not grounded or something.

First question: Which is the true issue?

Second question assuming the all-knowing Google was correct: What do I do? Finances are tight but I’m hearing that diagnosing the problem will be something that takes lots of time and therefore lots of money. Is there anything I can do to try and fix the problem? Or am I going to have to come up with a few hundred $$$ to get this diagnosed and corrected?

Also, is it harming anything that I still drive it like this? It runs still. It doesn’t run as well as it did before the light started

(I hit ‘post’ by mistake before I was done! Oops! =D)
…started coming on. It can idle really crappy too. When it first started, the light wouldn’t come on until I’d either gone a few miles or until I’d go about 30MPH or so. I could tell when it was going to come on due to the way it would run.

And sometimes the light doesn’t come on at all and the car runs perfectly. It could be a total fluke, but from what I’ve seen is that the light doesn’t come on if I drive more than just a few miles (10+) and restart the car within about 10-30 minutes.

Any help would be appreciated! Even if it isn’t something I can fix myself, I like to know the workings and mis-workings of things.


Prynce, Check The Wiring And Connector For The Distributor’s Ignition Module. I’d Unplug The Connection And See What It Looks Like.


I Found Something Else. Click This Link And Then Scroll Down (Past The Chart) To Code 42.