A friend of mine came to work this morning and noticed that his fuel pressure gauge kept fluctuating between 1.5 to 12 lbs. He has a 2001 HO. He has the vulcan pump location kit on the truck and he thought that maybe the isolator for the isspro gauge was causing this fluctuation(it would normally stay around 12 psi but would occasionally drop for no reason for a moment). He pulled the codes and came up with the following:
P PCU
PO500
P DONE
P ECU
P1693
P DONE

The above is in the order the codes were displayed. I found that the PO 500 was something to do with the vehicle speed sensor 1 circuit or no vehicle reference signal 1. what exactly does this one mean?

The only thing I could find on P 1693 was a post saying it was believed to be a companion code to 1690 indicating low fuel pressure.

I am sure the lift pump is toast even though it is nearly new but I just wanted to be sure this is correct.

thanks
David

 

the vss is on the rearend (I beleave) check the plug on it. I've seen that code with wheel spin. These codes have nothing to do with the fuel pressure. That could be geled fuel, glogged filter, or as you say bad pump

 

Looks like the truck computer and the engine computer both know he's been spinning his tires. He does need to get a reliable fuel pressure reading though.
If the truck is acting funny, it might pay to get the computer scanned with a regular scan tool at most repair shops.