Yes, I did find this info on the net, but it was from Cat SIS (Service Information System). In other words, you need Cat passwords for access.

I have attached a wire diagram for a 3406C engine with a 4CK prefix. Yours may or may NOT be the same. I would need your full engine serial number to be sure, as there was more than one variety of that engine made.

Note on page one of the diagram, it shows a "transducer module" on the back of the injection pump. The boost sensor is located inside this housing. Wiring from the boost sensor then goes out to the ECM (see page 2).

There should be a hose attached to the intake manifold that goes to the transducer module so the pressure sensor can sense boost. If this hose were loose or bad, it would not throw a code (it would simply have low power since the sensor was reading low boost), so I suspect a sensor or wiring issue, most likely the sensor. If it is the sensor, that could be spendy, and I would look into maybe converting it over to a later 3406E remote style sensor.

One final note: I am not CATguy. I have a fair bit of experience with later model Cats (specifically 3406Es, C15s, etc.), but I am no expert. I also have to be a Detroit guy, Cummins freak, International wizard, and even a Mack guru from time to time. In other words, I am a jack of all trades, but a master of none. I'm certainly no Cat PEEC expert, and as I understand, no-one out there really wants to be, for good reason.

Cat 3406C Wire Diagram.pdf (965KB - 2444 downloads)