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Ron
Ron, ASE Certified Technician
Category: Ford
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Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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1994 Ford F250: fuel injection, automatic transmission..shifting

Customer Question

I have a 1994 Ford F250 4x4 with 7.5 L engine, fuel injection, automatic transmission. It suddenly started shifting erratically and at the same time the spedometer quit working. What is the most likely cause?
Submitted: 5 years ago.
Category: Ford
Expert:  Ron replied 5 years ago.

HiCustomer

 

Thank you for asking your question on JustAnswer.

 

The transmission shift points on your 1994 F 250 are controlled by the PSOM (Programmable Speedometer/Odometer Module ) which is the Speedometer and when it fails, the transmission will act as it acting. The fix is to remove the cluster assembly and have the speedometer repaired (PSOM). In most cases this has to be done at the dealer so the proper mileage can be programmed into the rebuilt unit.

 

 

 

The Programable Speedometer/Odometer Module includes the Speedometer, the Odometer, and the Trip Odometer, all of which are electronically controlled by a programmable integrated microprocessor. The microprocessor receives a speed signal input from the Differential Speed Sensor (DSS), and uses a programmed conversion constant to convert the signal to the standard 8000 pulses per mile speed signal output. The Programmable Speedometer/Odometer Module is serviceable only as a unit.

The electric analog speedometer receives it's input from the anti-lock brake sensor. The liquid crystal display (LCD) odometer is a combination trip odometer and total odometer. The total odometer is normally displayed. To See the trip odometer, press and release the SELECT button on the upper right side of the speedometer. To zero out the trip odometer, press and release the RESET button on the upper left side of the speedometer while the trip odometer is displayed. If the trip odometer is displayed, press and release the SELECT button to return the display to the total odometer value. The speedometer, containing the trip odometer and total mileage odometer, is serviceable only as a unit.

The speedometer is also used to provide Speed signal for correct operation of the vehicle's EEC module and speed control (if so equipped). Because of this, it is VERY IMPORTANT to change the speedometer's internal conversion constant if the size of tires on the vehicle is changed. Changing the conversion constant to the proper value when the tires are changed will also make sure that the speedometer retains the original factory-set accuracy

Customer: replied 5 years ago.

Is there anything else I should check? A fuse or open circut that has broken the connection to the speedometer?

Expert:  Ron replied 5 years ago.

HiCustomer

 

Thank you for asking your question on JustAnswer.

 

 

Ford has this TSB that you can check . If this checks ok and the #8 fuse is good then suspect the PSOM.

 

 

Article No.
94-9-12

 

05/04/94

^INSTRUMENT PANEL - ELECTRICAL INSTRUMENT PSOM (PROGRAMMABLE SPEEDOMETER/ODOMETER MODULE) DOES NOT FUNCTION PROPERLY AND # XXXXX FUSE BLOWN - VEHICLES BUILT THROUGH 12/7/93

 

^TRANSMISSION - E40D - HARSH SHIFT - VEHICLES BUILT THROUGH 12/7/93

 

LIGHT TRUCK:
1994 BRONCO, F-150, F-250, F-350

 

ISSUE:
The instrument Panel Electrical PSOM (Programmable Speedometer/Odometer Module) may be inoperative or not function properly and the # XXXXX fuse may be blown. In addition, if the vehicle is equipped with an E40D transmission, it may exhibit a harsh shift. These conditions may be caused by trim screws installed through the 17K745 visor wire between the left hand "A" pillar and the left hand visor bullet connector.

 

ACTION:
Tape the damaged or exposed wire conductor and add scrolling to protect the wiring from trim screw shorts. Refer to the following service procedures for service details.

 

1.Remove the garnish moulding. Refer to the 1994 ECONOLINE, F-150-350, Bronco F-Super Duty Service Manual, Page 01-05A-5, for the removal procedure.

 

a.Inspect the wiring condition against the trim screws.

 

b.Check screws for burn marks.

 

2.If burn mark is found, use electrical tape to protect exposed/damaged wire. Add 1/4" (6.35 mm) scrolling to maximize protection.

 

3.Replace # XXXXX fuse.

 

4.Reset the PSOM to see if it is functioning properly. Refer to the 1994 ECONOLINE, F-150-350, Bronco F-Super Duty Service Manual, Page 13-01A-8, for the reset procedure.

 

5.Reinstall trim. Refer to the 1994 ECONOLINE, F-150-350, Bronco F-Super Duty Service Manual, Page 01-05A-5, for the installation procedure.

 

6.Recheck fuse # XXXXX and PSOM final verification.

 

Customer: replied 5 years ago.
Last question: It is about 90 miles to the nearest Ford dealer. Is there any chance I can replace the PSOM without the help of a dealer?
Expert:  Ron replied 5 years ago.
Yes if you can find one , the only thing that will not be right is the mileage will not be actual as this has to be programed in, the dealer usually sends the cluster out to have this done.
Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 27634
Experience: 23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
Ron and 7 other Ford Specialists are ready to help you
Customer: replied 5 years ago.
Thanks for your help.
Expert:  Ron replied 5 years ago.
Your very welcome, thank you very much as well.

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Ron
Ron
Automotive Tech
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23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs