So, nobody has EVER fixed their speedometer.

[SJBikesaws]

98 Expedition 5.4 EB

My wife was driving it a few weeks ago, and the speedo shot up to 100 mph, then flat lined. Followed by bad shifting. Stuck my ODB2 scanner on it and I am reading P0500 only.

Hunted through ALL relays, and ALL fuses. All I did was fix the power socket to the rear, I guess my kids can charge their Ipods now.

Changed the VSS sensor.

No change.

Changed the ABS sensor.

No change.

Pulled the transfer case apart, the gear was good.

chased the harness looking for grounds and bad connectors, none found.

Jacked the vehicle up, ran it in gear at various speeds and was able to get signal from both sensors all the way to the black and white wire in the back of the cluster, so I figured a bad speedo head. Changed it out.

NO CHANGE!!!!

I am in a dry climate, the car hasn't been wet for a while so I am doubting I got the GEM wet. I have no other symptoms that would indicate the GEM???

I keep seeing issues like this all over forums (Truck and Expedition) WITH NO RESOLVE. Whats the deal, the speedometer dies and you junk the vehicle out????

Any body EVER find the problem with theirs???? ANY Feedback?


I have been through every other "normal" Expedition problem so far in the few years I have owned this POS (air suspension to real spring swap, bad COP's, blown a spark plug out the third back passenger side, rotted vacume fitting, changed the heater core and blend door, etc.). But this one has me stumped, I'm am sick of tossing money at a problem that I cant get rid of.

I am a heavy equipment mechanic, I run through this kind of crap for a living but I'm am stumped on this one. Of course, when its your own vehicle, Murphy strikes.

 

[1stGeExpedition]

Here's one...

http://m.ford-trucks.com/forums/showthread.php?t=1143832&styleid=20

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[SJBikesaws]

Well, I haven't gave up. Went back and chased wire again yesterday. Pretty much the entire path of the of the ground (pink and orange) and the analog AC signal (grey and black). After some phone calls with a friend that was a dealer mechanic and the Expedition guy when this thing hit the road, and a few hours hunting the path through my On Demand 5 digital manuals, everything points to the PCM. So, that will be the next hunk of cash thrown at it.


And YES, I will leave a full report here so the next guy knows what to look for and where to go (something the internet has REALLY lacked so far).

 

[gteater97]

I work on diesels everyday and im just tired of messing with this thing....I dropped mine off at a shop in town so I will know something tomorrow.

 

[stamp11127]

Before changing the pcm I would reseat all connections to it plus the 3 large connectors on the firewall driver side. Check for corrosion on the pins also. This is no different from the heavy trucks, parts are just smaller and considerably lighter - electronics are similar.

 

[01yellerCobra]

What controls the needle? Is it a stepper motor?

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[1stGeExpedition]

Hope you guys figure it out. It's something that I'm sure most of us will encounter at sometime or another.

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[gteater97]

So it was at the shop all day and they say PCM.....is going to check those plugs tomorrow. Anyone know if a new PCM has to be flashed

 

[bedrck46]

yes the NEW PCM needs to programed

 

[stamp11127]

Yep and tied to the instrument cluster. Not sure on these speedo heads but the old style used magnetic field strength to move the needle. If your handy with a soldering iron I would go over all the solder joints on the cluster. It is known for cold solder joint on the odometer might get lucky on this one.
What data are they using to fail the pcm?