I have a 99 civic hx coupe, it has the d16y5 block with the d16y8 head, ecu and intake manifold basically making it an ex (done by previous owner). I have two check engine lights, one is p0452 (fuel tank pressure sensor) and p0450 pending(Evaporative Emission System Pressure Sensor/Switch). I replaced all the sensors on the bracket above the fuel tank with ones from the junkyard and got a new gas cap and the check engine lights still come on. I’ve reset the ecu and disconnected the battery and they still come back on after about 20 miles or two days. I was just wondering if anyone has had similar problems or knows how to check for the problem.

 

You can try to install a 10k potentiometer in place of the FTP sensor, and adjust it to between 2.4V and 4V until the P0452 code goes away, similar to what is described in post #11 of this thread: https://honda-tech.com/forums/acura-...ltage-1201612/

On a 99 Civic:
Reference voltage from PCM – Yel/Blue wire
Fuel tank pressure sensor input to PCM – Lt Grn wire
Sensor Ground from PCM – Grn/Blk wire


image source: https://quartzcomponents.com/products/10k-potentiometer

There are other styles of potentiometers.

 

Is it possibly my ecu? My ecu code it 37820-p2p-335 and from what I’m looking at I think that’s the ecu from the 96-98 model and mine is a 99.