Code P0452, Fuel Tank Drop

[H2ummer]

Out of the blue I am getting Code P0452, Evap, Emiisions Systems, Pressure Sensor/Switch Low Input. This seems to be a pretty rare code I believe. I see the pressure switch is located on top of the fuel tank. Assuming the switch is bad, It looks like you have to drop the fuel tank to replace it. Has anyone done this? How difficult is the fuel tank to actually drop in your driveway? From reading the service manual on dropping the tank, it does not seem that hard but having never done it, just wondered what problems others have encountered doing it. Anything to beware of? I hate those line connectors going into the CVS canister and I am guessing there will be a few of those types to deal with.

[HUMTECH]

Ignition OFF, disconnect the harness connector at the FTP sensor.
 2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 2 and ground.
⇒ If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
 3. Ignition ON, test for 4.8?5.2 volts between the 5-volt reference circuit terminal 3 and ground.
⇒ If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
⇒ If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
 4. Verify the scan tool FTP sensor parameter is less than 0.2 volts.
⇒ If greater than the specified range, test the signal circuit terminal 1 for a short to voltage. If the circuit tests normal, replace the ECM.
 5. Install a 3A fused jumper wire between the signal circuit terminal 1 and the 5-volt reference circuit terminal 3. Verify the scan tool FTP sensor parameter is greater than 4.7 volts.
⇒ If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
 6. If all circuits test normal, test or replace the FTP sensor.

[LoJac963]

^that guy is awesome!

If you have to drop the tank it is pretty easy, easier than most IMO. I had to drop mine when I installed my aftermarket rear control arms. I would definitely recommend it being as empty of gas as you can! I believe there's only 4 bolts for the straps, disconnect the filler neck and slowly let it down, make sure nothing else is catching as you bring it down.

[H2ummer]

Originally Posted by HUMTECH

Ignition OFF, disconnect the harness connector at the FTP sensor.
 2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 2 and ground.
⇒ If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
 3. Ignition ON, test for 4.8–5.2 volts between the 5-volt reference circuit terminal 3 and ground.
⇒ If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
⇒ If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
 4. Verify the scan tool FTP sensor parameter is less than 0.2 volts.
⇒ If greater than the specified range, test the signal circuit terminal 1 for a short to voltage. If the circuit tests normal, replace the ECM.
 5. Install a 3A fused jumper wire between the signal circuit terminal 1 and the 5-volt reference circuit terminal 3. Verify the scan tool FTP sensor parameter is greater than 4.7 volts.
⇒ If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
 6. If all circuits test normal, test or replace the FTP sensor.

HumTech,
In your experience, would you say it is the ECM more times than it is the FTP sensor? Still have to drop the tank to make those measurements, so probably should just replace the FTP if you have the tank down anyway? It is not that much.

Oh and I guess if you replace the ECM and buy one online, that you cant just replace it, you have to take it to the dealer to get it programmed before you install it?

Thoughts?

[HUMTECH]

I would bet on ftp sensor or a bad circuit before ecm. Never seen an ecm cause this particular code. If you did need a ecm you need dealer to install and program it. If you install it you would have to tow it to dealer as it wont start. you should be able to get to sensor if you just lower tank about 4 or so inches. you can easily build a jig to hold tank and attach it to a floor jack that way you don't end up dropping the tank and breaking anything.

[HUMTECH]

You could also disconnect the ac pressure switch and see if code still sets. ac pressure switch shares the same 5v ref circuit out of ecm