I have a 2006 Ford Expedition Eddie Baur with the 5.4L and a 4R75E Trans sitting at about 130k miles. About a month ago my wife was driving it and it started 'driving funny' When she brought it home I took a look and noticed that the Check Engine Light was on and the O/D light was flashing. I hooked up my code reader and got these results:

Vehicle Manufacturer: Ford
Vehicle Calibration ID: TEDM8A2.HEX
Current Fault Log ------------------
P0141: O2 Sensor Heater Circuit (Bank 1 Sensor 2)
P0161: O2 Sensor Heater Circuit (Bank 2 Sensor 2)
P0743: Torque Converter Clutch Circuit Electrical
P0750: Shift Solenoid "A"
P0755: Unknown code - More information may be available on the web
P0962: Unknown code - More information may be available on the web

Pending Fault Log ------------------
ECU reports no pending faults
Historic Fault Log ------------------
ECU reports no historic faults
Other discovered fault codes (possibly pending, current or manufacturer specific) ----------------------------------------------------
P0731: Gear 1 Incorrect Ratio
P0740: Torque Converter Clutch Circuit
P0748: Pressure Control Solenoid "A" Electrical
P0753: Shift Solenoid "A" Electrical P0758: Shift Solenoid "B" Electrical
B1360: Unknown code - More information may be available on the web
U1900: Unknown code - More information may be available on the web


I sent the truck to a good friend of the family that owns a transmission shop. He diagnosed it and told me it needed a full rebuild. I gave him the go ahead and he did the rebuild including new valve body, internal harness, Torque Converter and all. When he was done, I went and picked up the truck and it drove fine for about a day. Then the same codes came back again. The codes cannot be reset. And the shifting is bass ackwards. The truck will start off in a higher gear, then downshift once you get above about 15MPH. At that point it wont shift out again until you come to a complete stop.

I took it back to him again and he couldn't find anything wrong so he called a shop to come take a look a the electrical system. They didn't do a full diagnostic, but after sitting for a week with no battery they discovered that a connector to the ECU was loose. The replaced a gasket on the connector fired it up and the codes were gone so they sent it home again. This time it lasted for about a week. It did fine until the day after a 70 mile trip.

The shop said the loose connector may have damaged the ECU. To eliminate it as a problem, I went ahead and bought an ECU and had it flashed. The truck drove for about 20 miles and guess what... Same codes again.

At this point, I (and the shop) are at a loss. I have no clue where to look next. I'm not sure if a loose ground somewhere on the truck could cause this or a failing sensor somewhere that is shorting.

A little more history, when the truck was a few months old, the main fuse blew going down the interstate. The Ford dealer tried to replace the fuse and send it home but I wasn't having it until they told me why the fuse blew. They had the truck for about 2 weeks and couldn't find anything. After I personally went back in the shop and spent 30 minutes running through the electrical schematics with the tech we identified a sensor in the transmission that did not have a secondary fuse in line. Upon them pulling the sensor, they discovered it was shorted and replaced it.

 

please feel free to email me direct at hileta@hotmail.com

 

The O2 wires probably are wrapped in the same loom as the transmission control wires. I'd start there by unlooming all the wires going to the O2s and transmission connector and start checking for shorts, chaffing, etc..You should probably remove the loom/tape all the way up to the computer connector if possible.

EDIT: Actually before that - Check Grounds! Especially any engine, transmission, or body grounds. Make sure all the grounds on the negative battery cable are secure and have continuity.

 

Thanks lead head. Thats where i will start. Any clue as to where i could get a copy of the electrical schematics for this thing?

 

I'm with Lead Head on this, because to me as well, it sounds like wiring damage. Unwrap the wiring harness that goes down to the tranny and inspect all of the wires.

 

It's $60 (used) but worth every penny in a situation like this. The Buy button is way over to the right. You might have to scroll the page over to see it.
2006 Ford Expedition & Lincoln Navigator Factory Wiring Diagrams

 

Thanks alloro! I found a copy on Amazon for $20 including shipping! Should have it next Monday!