View Full Version : Fuel Tank Pressure Sensor, fault codes P0452 and P0453

05-27-2009, 11:09 PM
My 98 Chevy S-10 left me stranded a few weeks ago when the fuel pump failed.

I replaced the old fuel pump with an AirTec purchased from AutoZone.

The job involved removing the tank to get at the fuel pump and replacing a 4 pin electric connector to fit the new fuel pump. For reliability I solder spliced the new connector instead of using the crimp splices that came with the new pump.

The task of replacing the fuel pump took me about six hours and when I was done the truck ran as good as ever no fuel leaks no problems.

Several weeks later my Service Engine light comes on, although the engine continues to run fine.

I went to AutoZone and ran a diagnostic. I got a fault code of P0452 and P0453, indicating a problem with the Fuel Tank Pressure Sensor, a component attached to the fuel pump unit I replaced. Why should a new unit go bad?

I hate the thought removing the gas tank again to trouble shoot this problem. If I botched the job or the part I replaced was defective why would it take several weeks to occur?

Aside from the obnoxious engine warning light the truck runs fine. Would it do any harm to ignore this problem?

05-28-2009, 06:26 AM
Are you positive your gas cap was on tight??

05-28-2009, 08:12 AM
i would take the battery off and let the lights go away. if they come back on right after you connect the battery again then there is a problem. but like "WHO" said have you checked your gas cap. that is a common result in codes showing for fuel pressure.

05-28-2009, 08:57 AM
I believe a better way to reset the computer is to take out the ignition fuse for twenty seconds.

In replacing the fuel pump every aspect of the job went well accept one little thing I botched up.

In attempting to siphon out the gas tank, I learned about the ball check valve at the base of the filler neck attached to a rubber hose connecting to the gas tank.

I learned the hard way it is impossible to get a siphon hose into the tank. When I withdrew the siphon hose I mangled up the metal flap valve where you fill the tank. This would leave only the gas cap and ball check valve to keep the gas tank airtight.

I think I'll try temporarily replacing the gas cap with a piece of saran rap and rubber band. This should make an airtight seal and extinguish the error, proving the fault is either the gas cap or flap valve.

If I still cant get the light extinguished, I'll try attaching a toy balloon to the filler neck by cutting off the tip and stretching it over the filler neck and applying a rubber band to hold it on (I never tried this but I think its possible). I"ll inflate the balloon and watch for it to deflate. Hopefully I'll be able to find any leak from the filler neck attachments to the O ring around the fuel pump.

If the the balloon stays inflated there are no leaks. The problem must be a faulty tank pressure switch or wiring.

05-28-2009, 09:10 AM
PS: This problem is puzzling. If my mangled flap valve or loose gas cap was the problem, It should have failed immediately after the job was done. Why did it take several weeks to develop?

I hate the thought of having to drop the tank or jack up the bed to repair leaks.

05-28-2009, 09:54 AM
not true. it could have happened when you got gas recently. you could have not put the cap back on correctly or what not.

05-28-2009, 01:19 PM
I always give the cap a good twist till I hear the sliding clicks. Interestingly the problem did occur after filling up. My gas cap was checked about a month ago as part of NM state Once every two year emissions inspection. I've been using the same locked gas cap for over 11 years. Never had a problem before.

The gas cap has been removed and installed since the initial fault, yet the fault persists.

I don't think the problem is gas cap related.

05-28-2009, 02:22 PM
if the cap is 11 years old then it might be time for a new one. the cap probably lossed the seal in it to keep it air tight. caps can go bad.lol. ut just took the dump that day.

05-28-2009, 02:52 PM
I checked the O ring seal on the gas cap and the mating surface of the filler neck, they are smooth no visible nicks or burs.

I wish it was the gas cap, but I think the problem would most likely be caused by my changing the fuel pump two weeks ago.

I have another Chevy S10 a 97, which I also changed the fuel pump after the one in my 98 failed. I don't ever want to be stranded for a fuel pump again. Both my 98 and 97 S10's now have new fuel pumps, the 97 has no problems though, I'll swap gas caps.

05-28-2009, 07:56 PM
The metal flap has nothing to do with it at all....Thats just there to keep gas from getting to the cap as much. Gas caps do go bad,seen a 09 Pointaic come in with 500 miles with a bad gas cap.

05-28-2009, 08:21 PM
It's not unheard of to get a faulty fuel pump... Why'd you drop the tank? You have a truck right? Just take the bed off...way easier.

05-28-2009, 08:49 PM
Definatly......Thats what I did, only took 30 minutes to get the bed off and 5 to get the pump out.

05-29-2009, 08:34 AM
I appreciate the intelligent thoughtful replies and comments from this forum.

The reason I dropped the tank was to be to clean it out if needed. Surprisingly there wasn't much dirt or condensation in the tank. (I usually never let it go below half tank). I would have been better off raising the bed with a jack to get at the pump.

Getting to Twin Rotors comments. I believe your trouble shooting approach would best solve my problem.

I will have to find where this evap line terminates and pressure check it. You say there's a green cap under the hood?

I recall my truck has two lines going forward from the pump along the chassis to the throttle body. One is a supply and the other a return line. The middle line (which I believe must be the Evap) went along the chassis toward the rear. I haven't routed it to its termination point yet.

What special equipment do you use to check the Evap lines? Could I improvise something (like an inflated balloon) to pressurize the system?

zerobudget S10
05-29-2009, 08:57 AM
What special equipment do you use to check the Evap lines? Could I improvise something (like an inflated balloon) to pressurize the system?

I like your way of thinking. Not sure if it would work but we need more people/ideas like this around here. :)

05-29-2009, 09:24 AM
that place twin rotor is talking about has a valve stem like a tire does. but its a little bigger if my memory is correct. i havent been around the 2nd gen ones in a while but i think i may be able to find a pic of my old motor and see if i can locate that valve for you.

05-29-2009, 09:31 AM
here is the cap on the 2.2L. you can barely see the green cap in the yellow circle.


05-29-2009, 12:43 PM
Thank you Mc Lovin and Twin rotor.

I just opened the hood and found the Green Cap labeled Evap port. It's attached to a plastic line next to the oil fill.

When I make my next trip into town I'll buy some toy balloons. I think I could attach one of those narrow party balloons to the Evap port without popping it.

Hopefully I'll be able to smell any gas leaks from the gas cap. I could also apply soapy water to the top of the tank. Hopefully a balloon will provide enough pressure.

I guess I can expect an initial massive deflation of the balloon as pressure fills the tank void. Fortunately I have a full tank.

05-29-2009, 02:30 PM
honestly i dont understand this trick you have with these balloons. i cant get the concept on how it will hold pressure when it will inflate (if it does since you have to have force (more that 4psi) behind it to blow it up). explain this troubleshooting process a little more in detail

05-29-2009, 07:09 PM
I simply want to apply a very low pressure to the Evap line. I thought a balloon would be cheaper then a piece of test equipment.

Well this after noon I tried my experiment. I couldn't fit the balloon down into that crevice where the Evap line is. So I fitted a piece of siphon hose to the Evap test point and the balloon to the other end. I expected to see the balloon deflate into the evap line. The balloon did not deflate. I took off the gas cap and the balloon would still not deflate.

Apparently this Evap line takes a bit more pressure then a balloon.

Interestingly my Service engine light is now extinguished.

I don't think I fixed the problem though. The service light has gone away and come back before.

I guess I'll have to come up with a better air pump then a balloon. I'll see what I can get next time I go to Harbor Freight. I'll be sure to keep any test pressure under 4 psi.

I appreciate all the info and help you guys provided.

05-30-2009, 08:14 AM
PS: the Evap test point didn't look a schraeder valve. I didn't see any stem in the center.

If it was a schraeder valve that would explain why a balloon couldn't push air into the system.

You guys gave me all the info I need to find the problem. I'll just have to get the proper air pump and take the time to troubleshoot.

06-03-2009, 04:36 PM
As I mentioned in a previous post I had no success trying to pressurize the Evap test point under the hood with a balloon, so I routed the tank line from the fuel pump to a black box in the rear next to the spare tire.

Apparently the Evap line under the hood is the Surge line from this black box in the rear.

I disconnected the Tank line from the black box and attached an inflated balloon. The balloon discharged air into the tank and deflated as expected.

I affixed a piece of seran rap to the filler neck with a rubber band making an airtight seal. I re inflated the balloon and attached it to the tank line.

The balloon would not deflate and I could find no leaks in the Evap lines or O ring around the fuel pump, I could see the tank was pressurized because the seran rap on the filler neck was puffed out. I removed the seran rap from the filler neck and attached the gas cap. I found no leaks from the tank or gas cap.

Unless the gas tank operates under higher pressures then an inflated balloon, I must come to the conclusion there are no leaks and the tank pressure switch is at fault.

My original problem was a faulty fuel pump which I replaced several weeks before the Service Engine light came on. Apparently my new fuel pump has a defective pressure switch.

My question for Twin Rotor; do I have to remove the fuel pump to replace this dam pressure switch?

06-08-2009, 04:06 PM
To whom ever is still following this post, it seems the problem has just gone away.

The Engine Service lamp has been out for the last six times I've driven my S10.
It seems the problem was caused by a sticky pressure switch which came with the new fuel pump.

I suspect the warning lamp could come back on, but I have another two years till the next smog check.

I thank all those who provided info.

03-26-2010, 09:31 AM

The Fuel Tank Pressure Sensor (1) is mounted on top of the modular fuel sender. The sensor measures the difference between the fuel vapor pressure (or vacuum) in the fuel tank and the outside air pressure. A three wire electrical harness connects it to the Powertrain Control Module (PCM).

The fuel tank pressure sensor is similar to the Manifold Absolute Pressure (MAP) sensor.


The PCM supplies a 5 volt reference signal and ground to the sensor. The sensor will return a voltage between 0.1 volts and 4.9 volts back to the PCM depending on the fuel vapor pressure in the fuel tank. When the fuel pressure in the fuel tank is equal to the outside air pressure, such as when the fuel cap is removed, the output voltage will be 1.3 volts to 1.7 volts.


A fault in the Fuel Tank Pressure Sensor will cause a DTC P0452 or P0453.

03-26-2010, 09:40 AM
To whom ever is still following this post, it seems the problem has just gone away.

The Engine Service lamp has been out for the last six times I've driven my S10.
It seems the problem was caused by a sticky pressure switch which came with the new fuel pump.

I suspect the warning lamp could come back on, but I have another two years till the next smog check.

I thank all those who provided info.

I don't think so, it sits on top of the pump look at arrow number 1.