We get many emails that go something like this:

Hey I have an OBD1 Honda ECU and I was started the car for the first time (or driving) and started to smell an electrical burning smell that I tracked down to the ECU. When I opened the ECU cover, I noticed a transistor in the space labeled "q31" was burnt or missing.  I was wondering if you guys could fix it if I sent it in or something. I don't know if I should be worried or if I can run the car again because I don't want to start a fire or something else.

No worries here, this is VERY common and that component burns is if you plug a 12 volt connector (usually the PURGE Control Solenoid connector) into a 5 volt sensor (usually Air Temp).  For some reason honda made all of those connectors the same on OBD1 Vehicles and this is a common issue.

If you don't need purge control (emissions device) and the car runs fine with no check engine lights, usually there is nothing to worry about.  I do suggest carefully cutting out the burnt component from the ECU though.

We do have a service to replace that transistor or you can purchase the transistor and install it yourself.  See the following links:

Replacement Transistor:


Service to repair and replace the Q31 Transistor in your ECU (you must ship this to us).