Additionally, ABS, TC, HDC, and CDL all work just fine.

 

I had P0501 on both my trucks. It's something of a generic code -- you need to read SLABS codes to find out the true problem. For all occasions where it occurred for me, it was a wheel sensor issue.

 

All right then. I stand corrected. I still need to pull the wheels and check the brakes as well as bleed them. The Nanocom has arrived, and I have an icarsoft as well, so I’ll run through detailed diagnostics of the SLABS and go from there and report back.

I agree it’s somewhat nebulous as despite the detail in the Rave, the sources look to have you chasing your tail a bit.

Thanks a bunch for the input.

 

As a matter of course, I ran the codes on the SLABS with the Nanocom today and nothing came up. Does anyone know what values I need to be looking at for live data to determine a corner I should be focusing on?

 

I’ve not followed up on this one for a bit as I had other fish to fry.

Current status:
- replaced both front hubs and WSSs (the Amigos did eventually come up)
- Now I have no Amigos, but the P0501 comes back pretty much immediately

The Amigos came on when I did the hub for the passenger front and the WSS tanked. I replaced the WSS and the Amigos were gone. In the interim (waiting for the new WSS) P0501 never came up. I figured this was due to the P1590 trumping the P0501 because it can’t determine the VSS value is implausible because it can’t get a reading from the WSS (say that fast 5 times).

So I am now back to thinking this is the VSS itself, as in the one above the valve body in the transmission. I think it is the VSS for a couple reasons:
1- No Amigos or anything of that nature (as I said before)
2- I don’t think it is a chaffed wire or the like because the code would then be P0500

This is all based on research in the Rave and what could cause this code. According to the Rave, the VSS reads a value I think in the same way as the WSS and captures that value from the output shaft of the transmission. I just hooked up the Nanocom and in the transmission section got P1884- CAN message V3 (Road speed) Invalid (FFH).

Then just hunting around I went into the Motronic faults and it read P1000. “Vehicle Speed Sensor signal error drive cycle B. Occurred 1 times. Signal invalid….”

I’m really thinking this has to all lead to a bad VSS? I mean what else could it be? There were zero faults in the SLABS section.

 

I just got a new code tonight which is really making me think something is up with the VSS. P0734: DTC P0734
Gear ratio monitoring (4th gear).

Possible causes by suggested order of priority:


Output shaft signal not to specification.
Engine management ECM faults present.
Open circuit C243/E (K) to C193/42 (R).
Open circuit C243/F (B) to C193/14 (B).
Shaft speed electrical interference.
connectors C243,EAT C193 .
Open circuit shaft speed sensorC193/14 (B) to C193/42 (R).
Shaft speed sensor fault.
Torque converter mechanical fault.
Gearbox mechanical fault.
Output Shaft Signal Not To Specification.


Based on this and that I got the P0501, I don’t know what else it could be. The thread I copied the above from had some good info in there, but given the P0501, I’m inclined to think the VSS is bad.

 

Just went for another very short drive after monkeying around with the Nanocom and nothing was wonky there (per the thread above you are supposed to see if road speed shows a value in Park and you rev the engine). I cleared the codes and once I started moving the P1884 came back right away and I suspect the next time I drive it with the UG hooked up, I’ll get the P0501 again.

I’m really pretty stumped.

 

@longtallsally Sorry I missed this mine appears to have been a defective high/low switch, once it was replaced the code has never returned. It is on the transfer case but on an 04 it can replaced with the case in place.

You can do a basic test of the switch by pressing the mode switch in low range, it should light up the M on the dash. If it does not it could be the switch.

 

You rock beyond measure!!! I could easily see this as the case because the T case was replaced prior to my purchase.

I just checked and in “M” mode in 4 low it works perfect. Could the switch still be bad?

 

@longtallsally it could be flakey mine would flicker out after about a minute of movement, then just quit. I also found S for sport mode was unreliable (had to find my notes). But it could still be bad, I am not sure if you can check it though.