Hi, I just replaced the vtec gasket on the 2000 civic ex, It was cold as heck out so I used a heat gun on the solenoid/head for about 20 minutes to keep the Loctite gaket sealer warm so it would cure. Now I am getting a po420 cel.
Do you think the 2 are related or just a coincidence
thanks
Steve

 

Doubtful.

You need to list the make and model of the car.

P0420 is the Catalytic System Efficiency Below Threshold

The service manual lists the probably causes as:

- Three Way Catalytic Converter
- Secondary Heated O2 Sensor

This is from the 96-00 civic service manual

 

2000 civic ex all stock
I did have to take the fuel injectors out and the throttle body off to be able to get a drill to fit (bolt broke off in the head at the vtec solenoid).