I changed the temp sender on my 1989 4.9l about two months ago because the old one was broken. When I replaced it the new sender's post was much larger than the older one so I had to open the connector up. The gauge worked but it was reading hot in the a to l range of normal. A few days ago it went past the l of normal and the ENGINE light came on ( not check engine) so I pulled off the road and let it cool down. I replaced the sender and now reads that the temperature is about on the middle of the gauge, so it seems that everything is working fine now. My question is "Is the Sender or the Gauge what causes the ENGINE light pop on or is it controlled by something else, and if something else, what?"

 

Goes to the gauge only. I'm guessing you overheated & the engine leaned out. o2 sensor.

 

What causes the ENGINE light to pop on?

 

He just said, if it overheated and leaned out, the o2 sensor could throw a code. That's what I got out of it anyway. I'd say the light definitely had something to do with overheating. When that red light comes on its kinda scary isn't it?

 

Maybe I should make it more interesting! "How I spent my summer vacation, when I overheated & the o2 sensor sensed a lean condition, causing the engine light to come on."by ymeski56. My thermostat pooched on me & blew the seam on my radiator, but I didn't get an engine lite out of it.

 

I know thats a possibility, but I am just wondering what other problems cause the ENGINE light to come on other htan overheating?

 

The ECU, unable to maintain a 14.68:1 air to fuel ratio.

 

Could that be due to the fact that I have a bad fuel regualtor and that I plugged the AIR injection system and one of the plugs are leaking?

 

Yep. Especially a bad fuel reg. the air injection is supposed to help cool the combustion chambers under load.

 

THanks for the help