Hey everyone, any help is greatly appreciated. I've been trying to troubleshoot some codes on the Accord and cannot figure out what is wrong.

The codes that are coming up are P0451 (P0451 Fuel Tank Pressure (FTP) Sensor Range/Performance Problem) and P0505 (P0505 Idle Control System Malfunction).

The symptoms are a fluctuating idle at start or when stopped. After driving the car for 15 or more minutes and I come to a stop the car will sometimes die (after slowing down and stopping). The transmission does slip in the initial gears.

I have:

• replaced the IAC valve (junkyard) and cleaned up the throttle body
• checked the fuel tank pressure sensor (seemed to be functioning)
• cleaned the PCV valve
• replaced PGM FI relay (from junkyard)
• checked the EGR and it does function, also I cleaned out the EGR valves.

One thing to note was when I checked the EGR I checked the power going to the EGR and I'm not sure if I was doing it correctly but I wasn't seeing the 5 volts coming through, but I'm not great at testing electrical stuff and it confuses me so I kinda disregarded it.

What do you guys recommend checking next? Do I need to bring it in somewhere for a smoke/dye test? Buying a FTP sensor and replace? Check the ECM? Again, any help is appreciated. Thanks!

 

I recommend not changing parts until you verify the issue. If you replace a working part with a bad used part, the troubleshooting gets much more difficult.

Sounds like you have 3 issues. The idle, the fuel tank pressure sensor, and the transmission slipping.

I recommended buying a shop manual. automanualsource.com has a PDF for $22.

Can your scanner read live data? This will help with the idle and fuel tank pressure.

I'd change the transmission fluid with Honda ATF and hope fresh fluid stops the slipping. Drain/refill/drive. Do this 3 times to exchange most did. If it doesn't improve shifting, the clutches are worn and the trans would need a rebuild. The 98-02 transmissions have a higher rate of failure especially on the v6 vs other generation accords.

 

Thanks for the reply!

I've done the transmission fluid service and that seemed to help but it is still slipping. I'm just going to wait it out till it's gone before rebuilding or purchasing a rebuilt one.

I was using the Torque app on my phone that does show some live data. Anything specific I should be looking at?

 

Look at the fuel track pressure to see what the engine computer reads.

For idle, throttle position sensor, coolant temp, map sensor, intake air temp.

Forgot to ask earlier, but was any work done in the car just before the idle issue or fuel tank pressure started?