Ford Focus RS Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
23 Posts
Discussion Starter #1
Back in mid march, I noticed a CEL upon cold start after a heavy/wet snowstorm. P0451 "Evaporative Emission System Pressure Sensor/Switch Range/Performance"

I believe my tank was full, but can't entirely remember. Cleared it and it stayed away for a few weeks. Next time I saw it was upon starting up in the gas station parking lot, immediately after filling the tank up. Might I add, it rained the night before, and the roads were still wet. No idea if rain/water is the issue, just a common denominator those 2 times.

Since then, I've cleared it and it's come maybe 4 more times. Not instantly after a fill up, sometimes at 3/4 tank, but the other times it's come on, it's seemed to be on cold start. I always let the gas pump click and don't ever "top off". I try to use Shell every chance I get.

After searching the interwebs, I've yet to see anything on this code regarding our cars, or even ST's. There are a bunch of random focus forums where they mention the code but I've yet to find a clear solution. I'm hoping it's just some silly sensor issue. My car's performance seems to be entirely unaffected. Just trying to avoid the dealer due to having a tune (unless you convince me otherwise.) Any help or guidance would be greatly appreciated.
 

·
Premium Member
Joined
·
490 Posts
Not sure where the sensors are located right now, but do not go to the dealer unless you can’t find the problem. The sensor is likely good because it works mostly. The electrical connector(s) likely just need disconnected, sprayed with contact cleaner and reconnected. The tank pressure sensors are usually located at the tank near the evap canister. I’m removing all the shielding under mine to clean the oil off, so maybe I’ll see the sensor and let you know. The problem with the cel is not really serious unless thevtank vent is somehow plugged up, draw a vacuum on the tank and the engine would quit.
 

·
Premium Member
Joined
·
712 Posts
@DirtyDeez did your issue solve itself or did you have to do anything to get rid of the CEL? If you cleaned the connector can you let me know where it was located?

We had a big snowstorm yesterday, the snow was quite wet/sticky and the wind at the airport I work at had it packed everywhere on the car (wheels, brakes, etc).

Car drove fine yesterday after work (apart from the wheels being unbalanced from the packed snow). Parked it in the garage so the packed snow in the wheels would melt down. Used it once yesterday after it all had melted, no CEL. Got the code this morning only.

Turns out I did exactly like you did when I got to work (I carry my scanner all the time in the trunk), I cleared the code in hopes it would not come back. Wasnt worried much given I had similar issues on other cars before after big storms.

Attached picture of the code reader, french description though!
 

Attachments

·
Registered
Joined
·
23 Posts
Discussion Starter #4
@Barroux hi, sorry for the delay, I haven’t checked this in a while. So it turns out the problem ended up being my fuel tank pressure sensor. At first, this was my own self diagnosis. I found out that the connector for this sensor is located in the most obscure, hard to reach area near the gas tank on the rear passenger side of the car. I was able to separate the connector after fighting it. I then sprayed it with electronics contact cleaner, but upon trying to reconnect it, I realized I cracked the plastic on the clip so the connectors wouldn’t stay together anymore. It was so tight, I couldn’t even apply electrical tape to maintain the connection. After a few days of driving, I realized that my idle was off and I seemed to have a minor rev hang/ghost throttle that wasn’t previously present. I then took it to the dealer, after clearing my tune. Not sure how I got away with this, because I know they can see the reset when they hook the car up, but I was able to have warranty work done. After wrongfully replacing my purge valve and the code immediately coming back, they then ran a fuel pressure test and saw the psi reading was low. A brand new fuel tank pressure sensor ultimately cleared the code. The rev hang issue was completely revised and I haven’t had a code since. I’d say this was about 4k or so miles ago. I would’ve replaced the sensor myself, but it involved getting on top of the fuel tank. I forget if this access is achieved from removing components from underneath, or from above through the rear seat. I never actually knew how the whole snow/water thing came into play, because the rev hang didn’t begin until I disconnected the sensor entirely. It’s almost as if it was getting wet, bringing up a false reading, but not actually becoming compromised. Hope this helps you!
 

·
Premium Member
Joined
·
712 Posts
@DirtyDeez thanks for your reply I will keep that in mind if it becomes a problem.

The check engine light has not been back since I cleared it but it might be a matter of time.

I’m happy to know it seems like it’s nothing too serious if it ever comes back.
 
1 - 5 of 5 Posts
Top