Yo DD!
Yes, scan it
run it around to heat the engine up and shift thru all gears incl Reverse.
then; turn off all accesories/lights, etc.
Do KOEO portion first
For Key On Engine Running (KOER) portion, the engine has to be @ normal operating temp.
Post any codes found here or look em up in my broncolinks.com site. I have a Search feature at top right section; sometimes you'll need to enter a 0 (Zero) and also try an O (letter O) for the PO____ Codes. Bec. some folks at the Links sites had data entry problems.
There could be a few factors causing the PSOM needle to jump & tranny to shift violently/eractically such as;
a damaged ABS tone ring/or shavings in the rear differential
a
bad ABS (also called VSS) Sensor or it/s connector/wiring (corroded connections/conductors)
other connectors along da path thru the 4WABS Control Module & then up to da PSOM (Speedo/odometer) and then to the EEC/Cruise Control/ Overhead Console if equipped
& of course a faulty PSOM; sometimes due to a loose or bad solder joint inside
My ABS Module was fried and caused the PSOM needle to jump wildly, tranny to downshift suddenly and AMBER ABS light to turn on; also had a DTC and check engine light.
Tone Ring Inspection; "Take off the rear diff cover. Check the Ring Tone gear. It is located on the left hand side of the ring gear. Look to see if any of the teeth have been notched (from debris floating around in the diff.) Usually a spider gear. If the ring tone gear has been notched, it will need to be replaced to fix your speedo reading. Jack it up and rotate the tires to look for the teeth to be notched/broken/bent..."
Source: by Bighibbi
VSS Tone Ring Damage pics in a 95 8.8
Source: by sackman9975 at
http://www.supermotors.net/registry/19344/67582
PSOM Pointer Waiver TSB 96-21-11 for 92-96; "..The speedometer needle may waver and or a light surge may occur on some vehicles...This may be due to slight dents/chips in either the exciter ring or the Vehicle Speed Sensor (VSS) and air gaps between the VSS and the exciter ring. Any slight dents, chips, etc., in either the exciter ring or VSS will create needle waver. Measure air gap between the VSS and exciter ring. It should be 0.38-0.51mm (0.015-0.020"). Check exciter ring runout per the same ring gear backface runout procedure of the appropriate model 1996 Powertrain/Drivetrain Service Manual, Section 05-00. Make sure the exciter ring is mounted correctly to the ring gear. If runout is more than 0.1mm (0.004"), perform the differential runout check per the procedure in the appropriate model 1996 Powertrain/Drivetrain Service Manual, Section 05-02A or 05-02D, to find cause and repair as needed. If all items listed above check good, replace the Instrument Cluster Assembly. Obtain the correct service part number from the Parts Catalogue and then contact the Electronic Odometer Exchange Center at (800) 259-9700 for U.S. Dealers and (800) 663-9974 for Canadian Dealers..." read more by Ford via miesk5 at
http://home.comcast.net/~miesk5/technical_service_bulletins.htm#PSOM%20Pointer%20Waiver%20TSB%2096-21-11%20for%2092-96
This is the Ford overall TSB, but we can go to the Jumpering 4WABS Module next
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Continuity Test Through 4WABS Module Connector in 93-96; "...jumper 14 to 21, & 39 to 22..." MIESK5 NOTE; I did this on our 96; The 4WABS Controller was toasted; 2 yard Controller's were also bad; NO RETURNS!
Source: by Steve83 (Steve, That dirty old truck) at fourdoorbronco.com ; "...jumper 14 to 21, & 39 to 22..." MIESK5 NOTE; See diagram. I did this on our 96; The 4WABS Control Module was toasted; 2 yard 4WABS Control Modules were also bad; NO RETURNS!
Source: by Steve83 (Steve, That dirty old truck) at
http://www.fourdoorbronco.com/board/showthread.php?t=5242t=102436&highlight=psom+4wabs&page=2
This is what Steve wrote in that thread;
In the 4WABS Module Connector; unplug it; You can jumper 14 to EITHER 21 or 22, and jumper 39 to the other (doesn't matter which way). You're trying to get the ABS (VSS) signal from the sensor directly to the PSOM. Look at that diagram again.
Just for clarity: jumper 14 to 21,
which in the 4WABS Connectors Diagrams for 93-96 is 14 (CKT 530, LG/Y)
http://www.supermotors.net/vehicles/registry/media/280768 by Steve83 (Steve, That dirty old truck) at SuperMotors.net
to 21 (CKT 519 (LG/BK)
& 39 (CKT 491 (O/LB)
to 22 (CKT 523, R/PK)
