P0452 Evap DTC

Discussion in 'Engine & Performance' started by mpsjr, Mar 29, 2012.

  1. mpsjr

    mpsjr Full Access Members

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    I posted this earlier in the Gen1 section, but haven't gotten any responses yet, so I figured I would post it here as well.

    A few months ago my fuel pump died, so I had a local shop replace it. A couple of weeks before, I'd had the same shop clear an O2 sensor code before we went on a long trip (2,400 miles). My truck had been parked for several years before I got it, so the O2 sensor issue wasn't a surprise.

    When I picked my truck up after getting the new fuel pump installed, my Service Engine Soon light was on. At first, I figured it was just the same O2 sensor issue that it had before the fuel pump went out so I didn't pay attention to it at the time. I eventually got it scanned at Autozone and they said it was DTC P0452.

    What complicates things is that I also noticed a hesitation problem with my truck after getting the new pump installed. In fact, it died as I was pulling out of the shop's parking lot. It never had the problem before, and I initially thought it was just air trapped in the line from having the new pump and filter installed. However, the problem never corrected itself, so this past weekend, I decided to put in another pump since the other one was still under warranty. Since the only change was the new pump, I thought that had to be the problem. After getting everything back together on Saturday, the DTC light was gone (THRILLED) as was the hesitation/stalling problem. However, on my way home this past Monday, the CEL came on for the same P0452 issue.

    My question is whether anyone knows what could be causing the problem, considering the symptoms it has, and the work that's already been done. I know the code is for low voltage at the FTP sensor, which could mean any number of things, but being that the voltage is low, I'm figuring it is probably a plugged solenoid or canister vent. Does this sound about right? I have checked the hoses and connections going to the EVAP canister and everything seems fine, and yes, my gas cap is on (I actually replaced it about a month ago). I do (sometimes) get a hissing sound when I pull the gas cap off after driving, which I know can mean the EVAP canister vent is blocked, but how would I go about fixing the problem. Should I be looking at something else first? Any help would be greatly appreciated.

    Thanks in advance.

    Matt
    1999 Expedition EB 4x2 5.4 (190,XXX)
     
  2. CARO'S98EB

    CARO'S98EB Full Access Members

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    that code is for an electrical problem not an evap leak. the fuel tank pressure sensor[ftp] is part of the fuel pump assembly. make sure it has been connected properly. if it has trace the wires and look for a break. the colors are grey/red and brown/white. it looks like they all come together with the fuel pump wires then split off. if it is not the connections or wires it is probably the pcm but I doubt it. here is the ford description of the code.



    P0452 - FTP Sensor Circuit Low Voltage Detected The PCM monitors the EVAP control system FTP sensor input signal to the PCM. The test fails when the signal average drops below a minimum allowable calibrated parameter. Contamination internal to FTP sensor connector
    Damaged PCM
    FTP circuit shorted to GND or SIG RTN
    Damaged FTP sensor
    FTP V PID reading less than 0.22 volt with key ON and engine OFF or during any engine operating mode indicates a hard fault.
     
  3. mpsjr

    mpsjr Full Access Members

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    As I understand the way the system works, the FTP sensor voltage drops as pressure increases. If there is an excess buildup of pressure in the fuel tank, the FTP sensor voltage will drop. A drop in voltage to .10 or lower for 2 consecutive test cycles will cause the P0452 DTC.

    My main concern is that I just don't know what to check to determine whether the pressure is building up too much in the tank, or if it is another problem (i.e. electrical). I don't want to start changing parts and have it turn out to be something as simple as a blocked purge valve or vent solenoid. Basically, I don't want to start changing parts that don't need changing.

    Thanks for the response.
     
  4. CARO'S98EB

    CARO'S98EB Full Access Members

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    It is an electrical problem 99% sure. ck the connections and wires. this codes only sets with the key on engine off not while it is running so the vapor management vavle and canister vent solenoids are not the problem. voltage as low as it takes to set the code would be a huge vacuum.
     
  5. mpsjr

    mpsjr Full Access Members

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    Gotcha. Other than a visual inspection of the wiring, plugs and harness, how do I check the voltage to find the problem?
     
  6. CARO'S98EB

    CARO'S98EB Full Access Members

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    i would ck very closely the wires around the tank and pump as this problem started after they were moved for the fuel pump replacement. I would ck the wires from the ftp sensor to the pcm for continuity [ohms] first if still nothing found ck for voltage drop using a load.
     
  7. mpsjr

    mpsjr Full Access Members

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    Ok. This is the second pump that I've put on since noticing the CEL. I thought the CEL and hesitation problem were interrelated and being caused by a bad aftermarket pump, but the new one is doing the exact same thing. My truck will predictably hesitate/stall when slowing down to a stop, but accelerating again before coming to a complete stop. For example, if I'm pulling up to a red light that changes before I stop, and I accelerate while slowing down, it will hesitate/stall/die and then pick back up. I'm assuming now that this is not related to the fuel pump but could be a separate issue? Since neither problem existed prior to my old pump going out, I thought the pump was the obvious culprit. Not so much.
     

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