Fuel Tank Pressure Sensor, code PO453

Tiny
RD66
  • MEMBER
  • 2008 KIA SPECTRA
  • 2.0L
  • 4 CYL
  • 2WD
  • MANUAL
  • 160,000 MILES
I have an Evap code PO453 Evaporative Control System Pressure Sensor High Input. I tested the pressure sensor; I'm getting 5 volts to it. And I probed the signal wire and got 2.5 volts, but when I added vacuum, the reading went up instead of down. It's supposed to go down, right?
Sunday, April 17th, 2022 AT 10:47 PM

35 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,154 POSTS
Hi,

To the best of my knowledge, yes, it should go down. It sounds like the sensor itself may be bad. Take a look through the pic below and confirm the voltages I mention are shown at each pin.

A) Key on engine off: Measure voltage between terminal 3 of the FTPS harness connector and chassis ground. You should have 5v.

B) Key on engine off: Measure voltage between terminal 1 of the FTPS harness connector and chassis ground. You should have 0V.

C) Key off: See pic 2 below for directions for signal ground.

Let me know if that is what you are getting. Note: Pic 1 is the connector pinout.

I will watch for your reply.

Joe

See pics below.
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Monday, April 18th, 2022 AT 5:42 PM
Tiny
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Thanks Joe, I'll get back to you.
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Monday, April 18th, 2022 AT 9:59 PM
Tiny
JACOBANDNICKOLAS
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You are very welcome. I look forward to hearing what is found.

Take care,

Joe
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Tuesday, April 19th, 2022 AT 4:38 PM
Tiny
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Okay Joe, I retested the pressure sensor and it passed. I'm still getting the code. Everything in the evap system has been replaced, even the gas cap. I have inspected the hoses the best I can but I see nothing wrong. What am I missing?
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Tuesday, April 19th, 2022 AT 9:01 PM
Tiny
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Hi,

If everything checks good, there has to be a leak. Since you are not noticing anything that appears to be leaking, at this point you need to smoke test the system.

Basically, smoke is injected into the evap system at a very low pressure. If there is a leak, smoke should exit at that point

You need a smoke machine to do this. I don't know if parts stores have anything like this to rent. You may need to have it done at a shop if you don't have the tool.

If the sensor checks good, the connections between the sensors are accurate, it should work. So, there has to be a leak.

The code itself indicates signal voltage is too high from the FTPS. To me, it sounds electrical, but everything is passing.

Look at the pic below. It indicates the code, what it means, and what are the possible causes.

Let me know your thoughts.

Take care,

Joe

See pic below.
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Wednesday, April 20th, 2022 AT 7:02 PM
Tiny
RD66
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I'm with you, I still think I'm missing something in the wiring. I'll let you know what I find if anything. It's been kind of intermittent. Thanks for your help, sir.
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Thursday, April 21st, 2022 AT 12:42 AM
Tiny
RD66
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Okay, Joe, I ran the check you gave me and had 0.34 ohms. So, I ran a new wire from the ECM to the pressure sensor and now have 0.00 ohms. The po543 went away. Now I have a po449. I replaced the vent valve so I'm assuming it's either another wire issue or the ECM.
Do you have a check I should do for this one?
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Thursday, April 21st, 2022 AT 3:34 PM
Tiny
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Hi,

It certainly seems like that is a good possibility.

I attached the diagnostics below for the P0449. It walks you through checking resistance and all checks.

Let me know if this helps or if you have other questions.

Take care,

Joe

See pics below.
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Thursday, April 21st, 2022 AT 4:52 PM
Tiny
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Awesome ! Thanks Joe, you have been a ton of help.
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Thursday, April 21st, 2022 AT 6:56 PM
Tiny
JACOBANDNICKOLAS
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Hi,

You are very welcome. I'm glad to know it's helping.

Take care and let me know if you have other questions.

Joe
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Thursday, April 21st, 2022 AT 8:48 PM
Tiny
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Okay, Mr. Joe, I have 00.5 ohms at best, what now, replace the wire?
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Friday, April 22nd, 2022 AT 2:13 PM
Tiny
JACOBANDNICKOLAS
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Hi,

That is what I would at least try. It sounds like you may have found it again.

Let me know if that takes care of the issue. I'm interested in knowing.

Joe
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Friday, April 22nd, 2022 AT 6:45 PM
Tiny
RD66
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Okay, I ran a temporary wire from the ECM connector to the vent valve connector. I'm still reading 00.5 ohms. I did find something though. A few months ago, I replaced the vent valve and the canister. I just ran a hot and a ground from the battery and the valve is not closing. I put another one in it and its holding vacuum and its closing, but it didn't solve the po449. Some of the hoses and clamps have been replaced and there don't seem to be any clogs.
I'm stumped! What next?
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Friday, April 22nd, 2022 AT 7:44 PM
Tiny
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Hi,

Did you delete the code, and it came back? I ask because of this. The Canister Closing Valve (CCV) closes off the air inlet into the canister for leak detection of the evap system.

If it wasn't closing, that would set the 449. P0449 is set if pressure is lower than the predetermined threshold which could result from the vent valve being stuck open.

Let me know.

Joe
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Friday, April 22nd, 2022 AT 8:46 PM
Tiny
RD66
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Yes, I deleted the code several times. It keeps coming back.
This is my (CCV) with it off the car, when I apply vacuum does both ends need to be sealed?
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Friday, April 22nd, 2022 AT 9:04 PM
Tiny
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Is this connector under the dash? (See message above also please)
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Saturday, April 23rd, 2022 AT 4:03 PM
Tiny
JACOBANDNICKOLAS
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Hi,

Yes, and yes. The connector is a little left of and above the throttle pedal.

Let me know if you are able to locate it.

Joe
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Saturday, April 23rd, 2022 AT 8:36 PM
Tiny
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Is this it?
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Monday, April 25th, 2022 AT 6:18 PM
Tiny
JACOBANDNICKOLAS
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Hi,

How many wires are going to the joint connection? Are they all solid yellow? Interestingly, I found every joint connector on the vehicle except CBGJC4. I am trying to confirm the wiring color in the schematics to make sure you have the correct one. However, I believe you do. However, other J/C's are yellow with an orange tracer, so let me know.

Let me know.

Joe
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Monday, April 25th, 2022 AT 6:54 PM
Tiny
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There are 5 wires all yellow with orange tracer.
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Monday, April 25th, 2022 AT 9:21 PM

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