Hello Ford Folks,

I have a frustrating and somewhat elusive problem, compounded by a mismatched drivetrain. Truck is 2006 F-350 with 5.4L 24V, furnished as incomplete vehicle, has Steelweld service body, short wheelbase, was a utility service truck in CA before I got it.

Here's the backstory - working on an unimproved jobsite many months ago, the rear end dropped down in sand, and the smack on the ground cracked the oil cooler. Result was a slow oil drip. So I take it to my mechanic, they investigate, oil is clean, they replace the cooler with a new FoMoCo part, but then it behaves oddly when they test drive it, and before it even comes back to me the engine corrodes from within because apparently the new FoMoCo oil cooler had a leak between the water side and the oil side. Whoops. They find frothy oil, it acts like seized bearings, etc. So they tow it to the nearest Ford dealer, open a warranty claim, and say "sorry!". For context, I am a general contractor, this is my work truck. I am pushed back to operating out of my 1992 Chevy farm truck. The dealer puts enough sawdust in it to make it run again (this is a conjecture), but they give it back to me and say "All's well!". One tank of gas later, it's seizing again, shuddering like mad, and barely makes it home from a desert jobsite in the summer. Not fun. When I limp it to them with the poor truck jumping and sputtering and shaking like mad in the service driveway, the dealer now admits we have a real problem, and (grudgingly) replaces the engine on a warranty claim.

Rather, they replace the engine with an undisclosed different year remanufactured engine. The valve covers now bear a label saying "2009 MODULAR 3V CYLINDER HEAD USAGE: USE ONLY 2008 MODEL RUNNING CHANGE SPARK PLUGS HJFS-24FP..." I can get the whole label text if it helps anyone in this mystery.

Fast forward about three months, and the automatic transmission throws code P0501 (vehicle speed sensor), flashes the "TOW/HAUL" light, shifts hard under load, and generally acts unhappily, and has weaker than usual power (hard to gauge with a 5.4 in a 350, I know, but it's spongier than usual). No major difference in my use of the truck prefaced this behavior.

My response thus far: Replace all 3 of the VSS units (two on the tranny, one on the rear diff labeled "ABS SENSOR", but the same type of magnetic pickup - and please tell me if I have missed anything in this circuit). Also to change tranny fluid and both filters. Old fluid was just old, not awful, and the pan magnet was only moderately furry with shavings, not sure how much I should expect. Filters were not visibly clogged.)

Performance of the tranny improved slightly, but still throws P0501 and flashes TOW/HAUL. If I actually click it into "TWO/HAUL" then it won't ever get out of 2nd gear. No fun, I have a backhoe to move.

Various forums suggest the next step is to replace the TCM (which is combo unit, it is also the ECM/PCM in these trucks). I'm game to do so, but here is the sticking point: What computer model year to use? It's not an '06 engine. It is an '06 tranny. The 5R110 continued to be used for several more model years, though, so I would guess (but check me) that the engine model year matters more. To confound matters further, there are two disconnected wires in the engine compartment, which were connected to the original engine (they are towards the brake system side, I can furnish photos if this matters, but I view it mostly as evidence that it's not a 1:1 engine swap). Also, the valve cover label is confusing - is it 2009 heads on a 2008 block? And of course the dealer does not return phone calls. The work order list they furnished does not include model years of parts used, which I asked for, but was not supplied.

My local Napa has confirmed that yep, there are a few different TCM/PCM/ECMs even within the model year, and the '09 is definitely not the same as the '06.

If after I swap the ECM/TCM the issue still persists, I will take it in to a mechanic I trust, but the good ones are all busy and backed up, and for a few hundred bucks I am willing to try the computer - if I have a good idea which one to use.

Being therefore at a loss, I turn to the collective advice of the forums. Any thoughts out there?
Many Thanks,
Phlummoxed in the Phoenix Area

 

That indicates that the input to the computer from the VSS is faulty.
There is only one VSS in the vehicle. It is located on top of the rear differential. There are no VSS units on the transmission. The two speed sensors on the transmission are the turbine speed sensor (TSS) and the output speed sensor (OSS.) Neither one can possibly set a code P0501 code. Only the VSS can do that.

That's just wishful thinking. If it is still setting the code it didn't improve.

Almost certainly a waste of time and money.

What brand VSS did you install? Was the new sensor an exact duplicate of the original? The circuit seems to be very sensitive to this sensor. Many aftermarket VSS sensors do not perform well. I recommend only using a Motorcraft sensor.