In order to test voltage to the fuel rail pressure sensor, do I need to ground the black lead from the multi-meter to the negative battery terminal or just to the ground in the connector itself? Which color wire is the signal wire?

Hope my question is clear and thanks in advance for any information.

 

If you were a fully equiped auto electrician you would have a 20ft lead on the neg of your Multimeter to clip on the battery negative. The neg is the only "true earth" on the car and using other connections will in some circumstances give you false information.
As for the positive probe you would have a pin chuck with a needle to probe direct into the wire ..it is fatal to pull connectors as you often disturb and then cure the fault when you re connect. ( see photo) Usually I have heat shrink over the length of the chuck.
I could not find the fuels pressure sensor in my diagrams ( year not specified) but in general the wire with the black trace is the earth.

 

Thanks for the info. I'll probably leave it to my shop to check it out. Actually the cause of the P0193 error code may have been a battery that was in it's final stages and didn't have enough voltage to fully power up the fuel pump. Just finished changing out the battery so I'll see how things turn out.

 

My understanding is that these codes come in when you are under some acceleration (high intake manifold pressure), and then suddenly close the throttle plate. It causes a drop in manifold pressure (high vacuum). Fuel pressure is meant to remain at 55psi as compared to the intake manifold. That intake pressure drop accompanying the closing of the throttle plate has to be followed by a drop in fuel pressure. That drop is effectuated by a pop valve located at the fuel pump in the tank. That valve can stick over time and not drop the fuel pressure, causing the sensor to run out of range and throw P0193.

The vanilla cure is of course a new pump assembly. Historically that was a very expensive proposition, although MUCH cheaper options have popped up on eBay recently. For now, best is to look into a proper fuel injector cleaner in the hope of clearing whatever ails the pop valve. Most here tend to trust the Techron line of cleaners. Be sure to follow the directions from the label as these types of cleaners make rubber swell when used in too high concentrations. IOW, more is not better in this case.

Best of luck, keep us posted.

 

Thanks for the information. Have been running injector and system cleaners but to no avail. Swapped out the battery and will give her a run on the highway to reset ECU values when time permits. I suspect the pump is fine as pressure is within specs and basically it runs well when warmed up, plus no strange sounds coming from the pump when priming. Might be a faulty fuel pressure sensor or a vacuum leak.

 

Have you actually read the fuel pressure live value on a reader like Torque? You might want to do that before chasing down possibly non existent wiring faults.

By the way if you are testing wiring for power and ground a test bulb is going to be better than using a multimeter - multimeters to test high impedances like inputs, test bulbs for loads.

 

The likely problem area is with the pop valve located at the fuel pump assembly, not the actual pump itself. Check pictures of the part on eBay. There is a fuel level sensor, an actual pump and hoses as part of the whole thing. The pop valve is housed in that assembly.