11-08-2013, 06:06 PM
No 4x4; this is a hard one...
2007 6.0. 4x4 lights on cluster light up during start then go out as normal. Move the dash switch, nothing. No clunk from transfer case, lights, hub lock, nothing. This is all in 4x4 high and low. And yes, 4x4low needs to be at a dead stop and in neutral. Still nothing. So here's a list of everything I have done/checked:
Pulled codes on my Snap On scanner; P1820, P1828, P1865
P1820 and P1828 are both relay circuit failure codes; lets start here...
Removed relays off of truck, both Ohm'ed out correctly across the coil (76 Ohms), and also switched the contacts when energized. But I still went and got brand new relays from Ford, no luck
I checked for constant power at the coil and battery input pins on both relay connections on the harness near the driver's battery - check. Full battery voltage at those 4 pins. So this tells me whatever switches the grounds on the relay coils is not doing its job.
So then I decide to swap out the 4x4 module behind the glove box. There was $170.00 well wasted. Same results...
Now, as for code P1865 from earlier, that is defined as "Transfer case motor encoder plate short to ground". In addition, the scanner picked up the encoder plate contacts... A, B, C, and D were all CLOSED even though the switch on the dash was set for 2wd (All should be 'open' except for 'C'). So with this information I thought for sure all these problems were being caused by a shorted out transfer case motor. I change it out - $130.00 well wasted. Same results...
So now I go to check continuity between the relay "power out" pins to the transfer case motor connector. That looked good on both relays.
Then I decide to go to the switch on the dash. Has power going to it; the 3rd wire is the hot wire from 4x4 module. I get battery voltage there. The switch by itself Ohm'ed out perfect in all three positions. So I know its not the switch on the panel.
So just to recap... this 4x4 system is not wanting to ground the relays when switched to either 4x4 mode on dash. New relays, power where it needs it, all fuses checked throughout the system, new 4x4 module, new transfer case motor. I don't know what it can be...