Hey, folks. I just finished a timing belt (kit), thermostat (180F instead of stock 170F), valve adjust, and accessory belt change on my 2002 Honda Civic EX with a D17A2 engine. The wildfire smoke and a family emergency pushed me to basically wait an extra 10 days in the middle of the job. It was literally hazardous (500+ ppm of pm2.5) to breathe air - so the battery was disconnected for a lot longer than normal.

On the first warm-up afterwards, trying to get the air out of the cooling system, a CEL showed up for the first time ever on this car. My friend has a very expensive Autel scan tool and had stopped by, so he hooked it up. We have both worked as mechanics before. Yada yada yada, the code that came up was P0132 Heated O2 sensor voltage high, and it showed 4V - which is impossible as far as I know for any oxygen sensor to produce except for if there is a short between the heater circuit (scan tool showed it was off) and the signal wire. O2 sensors (not sure about widebands, but this is not a wideband) only produce 0.1-0.9V. The chemistry of the sensors makes it impossible for it to produce more than 0.9V.

Once, when fixing my friend's car, a 90s toyota tercel, it came up with a similar code that was about the oxygen sensor, but the code had been mis-translated or something and was actually supposed to say coolant temperature out of range. It has been a long time, so maybe I have it backwards, but this reminds me of that a little.

Anyway - Is it normal to have a CEL on the first startup after a coolant change?
It seems really coincidental that the O2 sensor voltage (the wiring is right next to the upper radiator hose) is crazy high now. Maybe I pulled one of the wires (the connection is heat-shrink butt connectors) loose in the process. When I ordered O2 sensors in the first place, the first set I bought was for a different engine. Now that I've written this out, I think I must have pulled one of the wires slightly loose.

 

No, it's not normal to catch an O2 high voltage CEL after a coolant change/timing kit.

I thought for the longest time each sensor had a 5V reference that they take as an input voltage and return varying values based on what is read, but I can't find that info in the manual at this time. It sounds like this thing completely failed and you're likely safe to get a new one if the wiring isn't clearly rubbed through or shorted out in the harness to your reference wire.

Anyway, here's the ECM troubleshooting guide to make sure before you toss parts at it: