Low Coolant / Service Eng. Soon Lights 1993 Lumina

I own a Chevy Lumina, 1993, 3.1 Ltr, V6, 188k miles. Outside of brake problems, I've been very happy with the car. About 3 months ago the "Low Coolant" light came on. After a new radiator and hoses, the "Low Coolant" light continued to come on, but it was intermittant. I returned to the shop, and they checked coolant levels and assured me that everything was fine. They said it was probably just a sensor. I decided to live with the problem and to check coolant level every few weeks.

Now I notice when I drive on the highway for about 15 minutes, the "Service Engine Soon" light pops on. This usaually happens after the "Low Coolant Light" has been on for a while-- but only when I drive on the highway for 10 min or so. If I turn off the car and wait a minute, the "Service Engine Soon" light goes off. This concerned me so I had all the oil changed and all the fluid level checked. The problem did not go away.

I took the vehicle To Autozone so they could get a code, but someone (perhaps a previous owner) cut the wires going to the cig. lighter.

Can anyone suggest what I should do next? I'd prefer not to go to a Chevy Dealer because the diagnosis will cost ~ $120. Should I bite the bullet or not?

You can paperclip the car, I believe, to retrieve the codes yourself. Jumper terminals A & B (to top right on my 91 cutlass) with the ignition on but engine off and count the SES light flashes. Codes are read as flashes: 1 flash, a pause and two flashes is a code 12, which is what you get whenever you jumper it. You should get three code 12's before you get anything else, IIRC.

As far as the coolant light, if the level's ok, then its most likely the sensor and/or wiring to it.

You can paperclip the car, I believe, to retrieve the codes yourself. Jumper terminals A & B (to top right on my 91 cutlass) with the ignition on but engine off and count the SES light flashes. Codes are read as flashes: 1 flash, a pause and two flashes is a code 12, which is what you get whenever you jumper it. You should get three code 12's before you get anything else, IIRC.

As far as the coolant light, if the level's ok, then its most likely the sensor and/or wiring to it.

look under the steering column for a connector. on my 1990 lumina you run a jumper wire between the 2 holes on the upper right.you will need a repair manual to translate the code....or post it here and i will look it up for you.

i am having simular problems, but much more severe. if you are interested see the thread Forums .com > Chevrolet > Lumina > intermittant stall/rough idle.

the service engine light goes on either because of your egr valve or you o2 sensor, once you hit i think 50 and slow down the light will come up.

Replace Your Low Coolant Sensor--i Think On The Right Side Of Your Radiator!!!!

The EGR system is tested when the car accelerates to 50 some odd mph and allowed to slow down with a closed throttle, so that's probably what that is.

I would test the low coolent sensor befor i replaced it (napa wants $70 for one). my car will illuminate the light even with the connector disconnected and the connector jumpered.
i didnt know the egr gets tested as described.