P0452 DTC low voltage at sensor

[Kallanon]

I have a 2000 SLE which is throwing up a P0452 (Evaporative Emission System Pressure Sensor/Switch Low). I've checked the voltage going into the sensor and found only 0.4 volts at the wire. I've pulled the plug behind the right rear wheel and found the voltage the same at this point.

At this point, the wiring goes into the trunk, and then behind and under the rear seat into what I would best describe as a river of wiring running through the battery compartment. I'm assuming the 5v is generated from the PCM, but have no idea which pin to check voltage at, or if there are any other points along the way I should check. If anyone can point me in the right direction for the next step I would appriciate it.

[bobgto65]

I looked this up in the shop manual for the 2004 3.8L and there is a 13 step process to diagnose this that seems somewhat complicated to me. But the fuel tank pressure sensor voltage is supposed to be greater than 0.1 volt on the dark green wire. The voltage varies depending on whether there is negative pressure/vacuum in the fuel tank (1.5 volts or more) or positive pressure (1.5 volts or less. )There is also a 5V gray reference circuit from the control module. At the sensor connector, the gray wire is 5V, the Black is low reference, and the dark green is the sensor signal. When the sensor voltage drops below 0.1V then the DTC P0452 is set.

The low reference, black is pin 80 of connector 1 at the PCM, 5V reference gray is pin 34 of PCM connector 2, and the signal wire, dark green is pin 55 Connector 2 on the PCM, check each wire for grounds, opens, and shorts or high resistance, and if all the wiring is good, replace the sensor. If you look closely at the PCM connectors, there should be pin numbers at each end.

[xdhd350]

The fuel pressure sensor is located on the fuel pump module and it can be accessed by pulling back the carpet in the trunk on the passenger side closest to the back seat. You will find an access panel held down by 7 sheet metal screws with a dust seal so remove it slowly so the seal isn't damaged. You will then see the plug for the fuel pressure sensor. The sensor itself is pushed into the top of the fuel pump module and can be replaced without taking the module out if the sensor itself is bad. It is held in by friction via a barbed rubber seal around the sensor port. Gently prying upward with a slight twisting motion will get it out.

Here is a link where someone replaced theirs... http://www.pontiacbonnevilleclub.com/fo ... 25859.html