2001 dodge ram 2500 van 318 /v8 2W /RWD

HI, 2001 DODGE RAM 2500 VAN 318/ V8 : DOES ANYONE KNOW WHY THE LDP HAS A WIRE, WT/BLUE TO THE ALTERNATOR AND EXACTLY WHAT PART THE CONNECTION PLAYS WITH THE LDP? IS IT THE MAIN PWR FEED TO THE LDP? AND IF I DO A SHORT TO GROUND TEST ON THE ORANGE WIRE DO I DO IT WITH THE LDP CONNECTED OR DISCONNECTED. I AM PURSUING A PROBLEM IN THE LDP CIRCUIT BECAUSE, NEITHER MY EVAP NOR CAT. MONITORS WOULD RUN NO MATTER HOW MANY TIMES I DO THE DRIVE CYCLE. THANK YOU. FRANK. [MY CAPITALS ARE JUST FOR EASIER READING]

Is it 1494 or 1495??

Flowchart below for 1494.

Here’s a flow chart for 1495

Hi John. Thanks for your response and the info. The code is p1494 although I did not know that the scanner had a code all this time. The only tests that I can do are volts and ohm and short to ground. I have a VOM but my scanner doesn't have bi-directional. What I would like to know is; is it normal for the 3wires on the LDP to have alternator voltage at the same time? Voltage is only there when the engine is running. If it has voltage, what could be wrong? The LDP is new. I'm not in the US, the van is old, and I have to order the parts, so I decided to replace the parts before they go bad. Thanks for your help, Frank

White and dark blue is gen source/alternator power.

White/Dark green has to be a ground in order to complete the circuit.


Here is a test. Disconnect the LDP and see if the orange wire still has battery voltage. Test lead on battery ground and and the other on the orange wire pin. If it does have alt voltage then you have a wiring problem.

You can do the same for the dark green wire. It should not have alt voltage with the LDP unplugged. If it doesn’t read anything, turn your meter down to 1v or 200mv if it can go that low and see what it reads. Sensor ground should not read above 100mv.

The important factor here is testing them while they’re NOT plugged in.

ok John I did those tests you suggested: ENGINE RUNNING/ ORANGE WIRE .026 V.025V .043V IT WAS CHANGING / ITS A RANGING METER
WT/GREEN 0.05V
WT/BLUE 13.7V

ENGINE NOT RUNNING WT/DG WIRE 0.03
ORANGE WIRE 0.00 0.01

NOW MOVING THE DMM TO mv : WT/GREEN 174.5 mv IGN OFF / IGN ON 11.0 mv
engine running 47.2mv. If I got the tests correct then the ground is way above the 100mv but I can't remember straight off what that is suppose to mean. bad ground? maybe ?

Hi John. All of your responses are going to my wife's e-mail. Is there any way that you can send them to 'frankiedon53@aol.com' which is mine. Thank you, Frank