I was thinking of using the "check gauges" light circuit to drive one of those 12 vdc piezo-electric buzzers from Radio Shack to warn of electric water pump failure (high temp) or oil pump failure (low pressure). I've seen the wiring diagrams (from "Shoebox" I think) but don't see a wire listed for the "check gauges" light or is it the #419 Brn/Wht line to PCM conn D, pin #9 that provides a ground for the light when necessary?

 

The check gauges light is not connected to the PCM.

D9 is for the "SES" (check engine) light.

I suspect the "check gauges" light may be internally wired in the cluster, since it only responds to instruments that are not driven off, or connected to, the PCM.

 

Thanks for the info. I got confused by the diagrams ... the instrument cluster pin-out calls it the SES (#419) and the PCM calls it the MIL but it's still #419.
I guess I'll try to get at the CES light itself. Is it actually a 12 v bulb? I hope it's not a 3 v led! It would be nice to have an audible alarm for impending mechanical doom!

 

They make a kit to do just that. I think it is called Water Pump Watchdog. Try a board search or Google.

 

Thanks for the suggestion. Though I'm sure you know half the fun is figuring out your own fix. I think that watchdog was doing some current draw measurements on an electric pump motor wasn't it? (I do have the old CSI pump) So it wouldn't help anyone with the stock or electric pump that had a hose leak that wasn't noticed.
I do wonder if the SES light comes on when the water temp goes too high or oil pressure too low along with the Check Gauges light. Luckily I've only seen the Check Gauges light once (no damage) but didn't notice if the SES light was also on. If it does then I could still break into the #419 line easily and not have to tear the dash apart (groan!)

 

There is no connection at all from the oil pressure sensor to the PCM, so there's no SES light for low oil pressure.

The coolant temp sensor in the head for the gauge is not connected to the PCM either. The coolant temp sensor for the PCM is in the water pump housing, and the PCM does a continuity check on the electrical circuit, and turns on the SES light and sets a DTC for high voltage on the temp sensor circuit when the circuit voltage goes over 4.9V. But that simply corresponds to an open circuit on the sensor, not set because a temperature reading is too high.

The dash instruments - oil, coolant, system voltage and fuel level - do not interface with the PCM in any way.

 

Rats!! Another hope dashed. I wonder why the design team would pick water temp (from the pump sensor) and evaluate it (I think, along with some other inputs) for air injection on/off, and which fuel map to use (cold/warm/hot) and not bother with alarms. They did so many other things so very well it seems surprising. Thanks again for sharing your information with us.