My CEL came on and I checked the codes. I had 6 (Coolant temperature sensor) and 15 (Ignition output signal). The last two repairs I made on this car were fixing a coolant leak which caused overheating and replacing the distributor, so I thought these codes might have been from those problems.

I reset the ECU and drove around for about 15 minutes to see if the CEL would come back on, which it did. When I got back to check the code now I only have the code 6. I checked the coolant temperature sensor and it is obvious just by looking at it that it needs to be replaced. So I guess I have three questions...

1.) It is possible the code 15 was still stored in the ECU from a previous problem or would that have made the CEL come on for the past 6 months? I' m wondering if I just didn't drive around long enough for the code 15 to register again.

2.) If it is likely the code 15 will come back, any suggestions about the most likely culprit to check (keeping in mind the distributor was replaced about 8 months ago)?

3.) The temperature gauge in the dash still goes up to the normal running level. Is it the temperature sensor that controls this gauge or is it the thermometer?

Your help would be greatly appreciated!

 

Code 6 is for the ECU's coolant temperature sensor. That one has a 2-wire plug. The smaller sensor with only 1 wire is for the dashboard gauge. They don't 'share' information between those different sensors.

Code 15 might have been stored from before, I don't know how long it remembers that stuff. When's the last time you ever had the battery disconnected?

There's several circuits between the distributor & ECU. The timing sensors (CYP, CKP, TDC) in the distributor have their own codes like 4, 8, & 9. The circuit from the ECU out to the ignitor is the one that can cause 15. Check & rule out any bad connections. But usually there would be other problems, like the engine wouldn't be running if that circuit was actually open.