The pressure sensor is located right here on the assembly. It’s a three-wire sensor with a five-volt reference, ground, and a return line to the computer.

Despite the truck having all new parts (injector, heater, tank, etc.), we diagnosed the issue. The book stated the code sets when the key is first turned on, specifically if the pressure sensor’s return voltage is under 0.2 volts.

We immediately hooked up a meter to the return wire (blue wire) and saw 4.4 volts. Since the code sets if the voltage is over four, this explains why the code was set.

We checked the five-volt reference and ground, and both were good. The question remained if the sensor itself was bad with the key on. To test this, we used a decade box to drop the resistance, bringing the voltage down to 0.18 volts.