2 added 163 characters in body
source | link

Replacing the broken fan switch seems to have made the CEL go away. My best guess is that the ECU starts monitoring the O2 sensor output as soon as this sensor reads that the engine is hot, and gets upset when the O2 sensor is actually still cold.

Edit: Nope, the CEL is back, and gas mileage has been really bad (around 18-19mpg on a car that usually gets 28-30 city and 40+ highway). Any better ideas?

Replacing the broken fan switch seems to have made the CEL go away. My best guess is that the ECU starts monitoring the O2 sensor output as soon as this sensor reads that the engine is hot, and gets upset when the O2 sensor is actually still cold.

Replacing the broken fan switch seems to have made the CEL go away. My best guess is that the ECU starts monitoring the O2 sensor output as soon as this sensor reads that the engine is hot, and gets upset when the O2 sensor is actually still cold.

Edit: Nope, the CEL is back, and gas mileage has been really bad (around 18-19mpg on a car that usually gets 28-30 city and 40+ highway). Any better ideas?

1
source | link

Replacing the broken fan switch seems to have made the CEL go away. My best guess is that the ECU starts monitoring the O2 sensor output as soon as this sensor reads that the engine is hot, and gets upset when the O2 sensor is actually still cold.