The Code says that the sensor is reading too high a value for the pressure in the tank. Usually too high means you'll have to replace the tank pressure sensor. However, before you do that you can test it. Read the following and check the link to figure out where the sensor is (I think its accessible from the access holes in the trunk) and check the wiring. Check the connection for corrosion, then the wiring. There are 3 pins on that connector. Looking at the pins, left most pin is #3, right most is #1. Make sure the car's been off for 5 minutes or so and take your ohmmeter between pin #2 and the ground. It should read 0 ohms. Then, keeping the sensor unplugged, turn the ignition on. Check the voltage between pin #3 and the ground, it should be 5V.

The instructions for changing it are as follows:

Tank pressure sensor, changing

Removing the tank pressure sensor
-Cut the cables tie from around the wiring harness.
-Bend aside the wiring harness.
-Undo the bolt and twist out the bracket and tank pressure sensor.
-Detach the fuel line holder from the tank pressure sensor.
-Remove the tank pressure sensor and XXX.


Fitting the tank pressure sensor
-Fit the fuel line and holder.
-Fit the tank pressure sensor.
-Twist back the bracket and secure it in place with the bolt.
-Return the wiring harness to its original position.
-Secure the wiring harness with cable ties.

This doesn't really help if you don't know whether you can cut through your floor or if they're is any sort of access without dropping it.. The only guess I have is that they don't say to drop the tank, so perhaps you don't. If you can take off the access points in the trunk and get to the wires.

Here's a parts list, the sensor is #35 which looks like its on the expansion tank above the normal tank, I'd open your cover holes first and hope for the best..

http://fhttp://farm6.static.flickr.com/5203/5281237195_378c63acea_b.jpg
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