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Got a real b!tch of a problem with one of the Bronco's we recently sold.It is a 94,5.0,e4od.electronic shift t-case.When the truck is cold everything is fine,but when it warms up is when the problems start.The speed sensor signal for the computer is dropping out after being driven for a while.The speedometer never stops working correctly,and the abs never acts up.I replaced the speed sensor on the back of the transfer case and it seemed to fix the problem,but it came back 2 days later acting up again.I brought it into the shop and put the rear on stands and put it in gear and watched the vehicle speed on my scanner.Sure enough,the speed on the scanner went to 0 mph,but the speedometer was reading about 40-45 mph.Out of aggravation I whacked the center of the floor in front of the console and the vehicle speed started to read again.I waited for it to act up again and whacked the floor again,started reading again.Ripped both the front seats out and traced the harness from the sensor to the transfer case shift module.Didn't find the harness to be damaged.Let it act up again and tried moving the harness around,no change,whacked the floor again and it started working again.I pulled the t-case module out and tried tapping it,twisting it and pulling on the wires and nothing changed.Thinking I might have a bad wire in the harness I cut and spliced in 2 new wires from the speed sensor to the t-case module,didn't fix the problem.Anybody have any other ideas.I am not sure which wires communicate the speed sensor info from the t-case module to the main computer.Need help with this asap or we are going to have to give the guy his money back
 

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You're working in the wrong spot. The t-case OSS is not the source of the speedo signal. It comes from the rear axle ABS sensor.

The ABS sensor sends a raw signal (108 pulses per rev) to the 4WABS module, which repeats that signal to the PSOM. The PSOM uses the conversion constant to change the raw signal to a standard 8,000 pulses per mile, and sends THAT signal out to the EEC, the cruise module, and the overhead console (for use by the thermometer). You should be diagnosing the Gy/Bk wire from the PSOM to the EEC, probably where it goes thru the firewall connector. If anything is attached to the left A-pillar, the wire to the console might have been damaged there. If anything is stowed in the engine bay near the cruise servo, check that harness.

Test-drive the truck with the scope attached and see if the cruise works when the signal falls off.
 

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Steve83 said:
You're working in the wrong spot. The t-case OSS is not the source of the speedo signal. It comes from the rear axle ABS sensor.

The ABS sensor sends a raw signal (108 pulses per rev) to the 4WABS module, which repeats that signal to the PSOM. The PSOM uses the conversion constant to change the raw signal to a standard 8,000 pulses per mile, and sends THAT signal out to the EEC, the cruise module, and the overhead console (for use by the thermometer). You should be diagnosing the Gy/Bk wire from the PSOM to the EEC, probably where it goes thru the firewall connector. If anything is attached to the left A-pillar, the wire to the console might have been damaged there. If anything is stowed in the engine bay near the cruise servo, check that harness.

Test-drive the truck with the scope attached and see if the cruise works when the signal falls off.
:stupid
 

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Jayrus said:
Got a real b!tch of a problem with one of the Bronco's we recently sold.It is a 94,5.0,e4od.electronic shift t-case.When the truck is cold everything is fine,but when it warms up is when the problems start.The speed sensor signal for the computer is dropping out after being driven for a while.The speedometer never stops working correctly,and the abs never acts up.I replaced the speed sensor on the back of the transfer case and it seemed to fix the problem,but it came back 2 days later acting up again.I brought it into the shop and put the rear on stands and put it in gear and watched the vehicle speed on my scanner.Sure enough,the speed on the scanner went to 0 mph,but the speedometer was reading about 40-45 mph.Out of aggravation I whacked the center of the floor in front of the console and the vehicle speed started to read again.I waited for it to act up again and whacked the floor again,started reading again.Ripped both the front seats out and traced the harness from the sensor to the transfer case shift module.Didn't find the harness to be damaged.Let it act up again and tried moving the harness around,no change,whacked the floor again and it started working again.I pulled the t-case module out and tried tapping it,twisting it and pulling on the wires and nothing changed.Thinking I might have a bad wire in the harness I cut and spliced in 2 new wires from the speed sensor to the t-case module,didn't fix the problem.Anybody have any other ideas.I am not sure which wires communicate the speed sensor info from the t-case module to the main computer.Need help with this asap or we are going to have to give the guy his money back
Back from dead....

Sorry to sneek in a bring and OLD thread back from the dead....I found this while searching the net for a problem with my F250. I am having the same problem.
I'll be driving and just completely randomly my OD cancel light will come on and I can not turn it back....then all of the sudden it will let me. Other times it is on when I start the truck and will let me switch it back off....
No pattern to it....
When the light is on by itself it seems to be in a limp mode and the tc will not look up.....
But at other tie it will not light up at all and will drive completely normal....
:banghead
Any Ideas?
Please help a fellow Ford guy. :thumbup

BTW I have this 95 F250, and a 73 Bronco....and it is full size (103" wheelbase, full width 60 frt, 35 spline 9" rear, coilovered and bugified) So it is sort of OK for e to be here.... :wacko
 
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