P0451

Bingo

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http://engine-codes.com/p0451.html

P0451 - Evaporative Emission Control System Pressure Sensor Range/Performance

Possible causes
- Faulty Evaporative Emission System (EVAP) Pressure Sensor
- Evaporative Emission System (EVAP) Pressure sensor harness is open or shorted
- Evaporative Emission System (EVAP) Pressure sensor circuit poor electrical connection
- Faulty Engine Control Module (ECM)

When is the code detected?
An improper voltage signal from EVAP control system pressure sensor is sent to Engine Control Module (ECM).

Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)

P0451 Description
The Evaporative Emission System (EVAP) control system pressure sensor detects pressure in the purge line. The sensor output voltage to the Engine Control Module (ECM) increases as pressure increases. The EVAP control system pressure sensor is not used to control the engine system. It is used only for on board diagnosis.

Situation is I was getting P0171/P0174 (bank 1/bank 2 lean) codes for a while. They'd pop up spontaneously and seemingly randomly. OK, might be an O2 sensor, but I monitored for a while. Now they've gone away. Related? Can a P0451 cause O2s to read lean?

A couple weeks ago, the P0451 popped up after refueling. I did not overfill, which seems to set it off. I have not experienced the fueling issue that a lot of 05-06 owners seem to complain about.

I tried swapping fuel caps with my truck, and the issue still exists, so I ruled out the fuel cap. The hoses under the vehicle look fine, so I have ruled that out as well.

I did have the water leak issue on the passenger side, and it screwed up my SJB...I had the electronics go haywire for a short while and I now have daytime running lights. This occurred at least a month before I got the P0451 code - could it be related? I thought the ECM controlled the EVAP stuff, not the SJB?

I'm just at a loss now as far as troubleshooting. I'm thinking it's the sensor, but how can I check that? It seems as if I'm gonna have to let a "professional" look at it which is the last thing I want to do. Thoughts?

_____________________

Just an update for posterity, if anyone comes across this thread. It was the fuel tank pressure sensor.
 
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BLKS197

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I'm sorry guys, but I'm going to bump this. Anyone know where to start looking to correct p0451. I am of the impression that it is the fuel tank pressure sensor, but I can't find any workshop manual to show me where it is. Please help me get this POS to pass NYS obdII inspection. Thank you!
 

07 Boss

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Reaching here but would a bad purge valve give you the code along with letting air into the intake past the maf? I would think it would have to be a huge leak if you're actually running lean.
 

BLKS197

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Reaching here but would a bad purge valve give you the code along with letting air into the intake past the maf? I would think it would have to be a huge leak if you're actually running lean.

Your guess is as good as mine. I was told that it is likely the fuel tank pressure sensor, and I was finally able to get some guidance as to where it is located.

I can log the purge valve to see if the voltage looks out of wack, but the car runs fine. AFR looks normal.
 

BLKS197

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In the hopes that this come in useful for someone else in the future, this code arises for an issue with the fuel tank pressure sensor. I logged the sensor with my SCT livewire and noted that I had zero voltage being read. I further tested the voltage by logging and using an air hose into the fuel filler neck to simulate an increase in pressure. From this, I concluded that the fuel tank pressure sensor was faulty.


I had no luck locating the part online, so I called a local ford dealership and acquired the sensor. I do not have the part number, but I was able to get it for about $150.00.


The sensor comes as part of a line which runs between the EVAP canister and the fuel tank, over the rear end assembly. Luckily, you will not need to use a lift and/or drop the tank. I was able to easily swap this line with some jack stands. You will need a 6mm socket (I believe) to unbolt one fastener. I also found it was easier to remove the old sensor and install the new sensor with the track bar unbolted. Otherwise, it is quick disconnects and plastic retainer clips.

I hope this can help someone in the future, because I know I wasted far too long trying to find the issue as well as the steps to replace the sensor.
 

shadad

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Hi,
sorry to raise this subject again, can anyone tell me where is that sensor location? any photo? :(
am having trouble finding this one. i have the same code p0451. i already replaced the fuel cap but no use. i looked down the car and i see the lines are connected.
 

Juice

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The P0451 is for a faulty sensor, not an evap leak.
This sensor is above the rear axle center section, in the middle of the car, attached to/part of that evap hose. Jacking up the body of the car and letting the rear suspension droop helps with access.
 

shadad

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The P0451 is for a faulty sensor, not an evap leak.
This sensor is above the rear axle center section, in the middle of the car, attached to/part of that evap hose. Jacking up the body of the car and letting the rear suspension droop helps with access.

can the P0451 also caused a P0455 ?! because i have these 2. first the P0451 pop first, then later the p0451 shows (like next day).

I have looked under the car and found it. 2 lines from both tanks connected to the Sensor and dont see any leak at all!
i think its a sensor as you mentioned. i will replace it and will update you. ( i already cleaned the fuel door and replaced the cap ).
 

Juice

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P0455 could have set before the pcm faulted the sensor itself.
 

shadad

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P0455 could have set before the pcm faulted the sensor itself.

I have screenshots from the ODBII, the P0451 always logged and showing way before the P0455.

what do you think? go with changing the Sensor? i dont see leak.

its worth mentioning that i changed the ECU and still not programming to factory settings yet (2nd hand)
 

Juice

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I would unplug the sensor first and see if there is any moisture in the connector. Any moisture in there can cause a problem.
IIRC, the sensor is actually part of that hose/line. But Im not 100% sure.
 

shadad

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I would unplug the sensor first and see if there is any moisture in the connector. Any moisture in there can cause a problem.
IIRC, the sensor is actually part of that hose/line. But Im not 100% sure.

I will do that and update you.
BTW it is part of the hose line. line from the right tank and line coming from the left line and the sensor right on the middle connecting both.
 

shadad

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I would unplug the sensor first and see if there is any moisture in the connector. Any moisture in there can cause a problem.
IIRC, the sensor is actually part of that hose/line. But Im not 100% sure.
Hi there :)

I replaced the fuel tank sensor and next day right on the 3rd cycle, the fuel tank cap warning alert disappeared from the dashboard during my driving to work :clap::beer:. the check engine still showing tho but its ok. at less now i know that the fuel cap i used to have was not the cause.

am going to wait today and tomorrow and see if the check engine goes away or might be another leak or another error.

i will update soon.
 

shadad

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Success ! :happythumbs:
3rd day not a single issue logged on ECU and no warning or check engine alert. all OK.

so, as i suspected, the P0451 was the root cause since it was first to appear and it was causing at less 2 Codes later after it pop up on the ECU.

thank you all.
 

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