while driving yesterday the check engine light and the VTM-4 light came on simultaneously. this came on just as I reached my destination so I turned the car off and let it sit for a few hours. when I got back and started the car the check engine light was still on but the VTM-4 was off, and after a few miles of driving the check engine light also went off. then today both lights came back on, and again when I turned the car off(this time for only a few minutes) and then started it the VTM-4 light was off, but then came back after a few minutes. this time both lights stayed on for me to use my obdII scanner and I got the p0131 code for the pre-cat O2 sensor, which seems like a not terribly difficult but very annoying job. my only worry is that in my searching I have not been able to find anyone else mentioning the VTM-4 light coming on with a bad O2 sensor and I don't want to spend money on something that might not be the problem. any insight on the situation would be greatly appreciated.

 

The pilot of this vintage I got to play with would also trigger the vtm light with the check engine light. In my case it was EGR misfire related.

I think it's just a programming goof.

 

thats what I saw some people mention online, but it seems weird that it would send a p0131 code if the o2 sensor has nothing to do with it. any recommendations on how I can test if it is an egr valve malfuction/how I would fix it?

 

In your case you probably need an o2 sensor.

Mine was a code specifically for misfires that was tracked down to some dummy ("professional" repair shop) installing the upper intake manifold gasket upside down. Blocking 4 of the 6 of the EGR ports making for a bad misfire when the EGR opened.

Just pointing out that a check engine light is accompanied by a VTM light because of a programming goof. There was nothing wrong with the VTM on my example.