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35 Posts
Discussion Starter #1
Friends Bronco but I recall reading about this over a year ago. My search lead me in two directions for Keith's problem.
One was the Speed Sensor in the rear diff
And the other was the Throttle Position Sensor

Keith said they recently changed the O2 sensor and the engine ran better.
Speedo acts up around 50-55mph and idle is high after coming down from that speed. Rough shift is at low end with first gear going up to about 2000 and then-- wham into second.
Another issue is that the temp guage reads high but the engine is not hot.

I appologize for not being able to wade thru the search results as some seemed to wander from the original diagnosis.
And thanks in advance.

Super Moderator
26,313 Posts
You had 173 (EGO not switching, Rich Exhaust Bank 1) and 634 (Manual lever
the O2 sensor was replaced and that 173 is gone now, right?

But you still have DTC 634;

DTC 67 & DTC 634; Manual Lever Position/Transmission Range (MLP/TR) Sensor Pin-Point Test in 92-96 Ford-E/F Series, Bronco; from Ford EVTM; "...No upshift 4th gear starts, harsh upshifts, neutrals out after shifts; Check the resistance of the MLPS: The resistance of the MLPS (pins 30 and 46).." read more
Source: by Ford via alldata &
and this is sim but less detailed than above;
"E4OD Nagging Neutral Nonsense & Pinpoint Test, Manual Manual Lever Position (MLPS) also called Transmission Range (TR) Sensor. Some of the problems the MLPS can cause are wrong gear starts, TCC hunting, no 4th gear, engine stalling, high or erratic line pressure & a sudden neutral condition; The negative lead of the multimeter should be placed at the MLPS signal-return ground terminal at the MLPS...This sensor is responsible for more malfunctions than any other sensor in the sys- tem, and the kicker is that it seldom stores a code 67 or 634..."
Source: by Pete L at
-- PSOM WAVER is next; I had this problem too, AMBER ABS Lamp was Lit; PSOM went beserk ; HARSH, NECK Snapping, ROUGH DOWN/Up shifts TCIL Flashing crazily...
Had a DTC P0500 (but this is in a 96 w/OBD!! My ABS Module was fried...

Did da store do the KOER part while engine was at Normal Operating Temp?
if not,
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 site
What Testing did you do? on VSS?
I see that you have good knowledge, but I'll go thru da drill anyway, ok?

is the Amber ABS light?

and/or check engine light lit?

If so, there could be other factors causing the PSOM needle to jump; 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
& of course a faulty PSOM; sometimes due to a loose or bad solder joint inside

VSS Tone Ring Damage pics in a 95 8.8
Source: by sackman9975 at

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 at

Pointer Waiver TSB 96-21-11 for 92-96; "...The speedometer needle may waver and/or a light surge may occur on some vehicles when speed control is used at highway speeds between 80-113 km/h (50-70 mph). 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..."
Source: by Ford via miesk5
This is the Ford overall TSB, but we can go to the Jumpering 4WABS Module next

PSOM Continuity Test Through 4WABS Control Module Connector in 93-96; "...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
This is what Steve wrote in that thread;
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,
[URL=""]which in the 4WABS Connectors Diagrams for 93-96 is 14 (CKT 530, LG/Y)[/URL]to 21 (CKT 519 (LG/BK)

& 39 (CKT 491 (O/LB)
to 22 (CKT 523, R/PK)

Wiring Diagram in 96 (similar to 92-95) & CHECK SPEED INPUT SIGNAL Test
Source: by Ford via Steve83 (Steve, That dirty old truck)
Next are the 4WABS Connectors Diagrams for 93-96
Source: by Steve83 (Steve, That dirty old truck) at
here it is in full Size, so you can print it out seperately from this post;

Engine Coolant Temperature Sender For Temperature;
Engine Coolant Temperature Sender for Temperature Gauge Defect TSB 95-13-2 for with a build date code prior to 2774 (277th day of 1994); PN F1SZ-10884-A; "...Factory temperature senders with a date code before 2774 are known to be defective. The code is stamped into the side of the hex. The format is the Julian date + the last digit of the year, so that's the 277th day of 1994. So 0085 is good; 1934 is bad; 3034 is good; 2765 is good; 3582 is bad. The sender should test at 74 Ohms cold; 9.7 Ohms hot. If you're having trouble with your temp gauge, try to read the date off the sender before any other diagnosis. A new sender from NAPA is under $10..." Testing; "...Pull the R/Wh wire straight off the sender & ground it to the block, intake, or head. Then turn the key to RUN. If the needle pegs, replace the sender. If not, diagnose the circuit
Source: by Ford via Steve83 (Steve, That dirty old truck) at

Location pic in a 94 5.8
Source: by Jeremy M (Big '92 jermil01) at

35 Posts
Discussion Starter #3
Thanks and printing suggestions with links

I have to forward your suggestions and attempt to get your answers re tests and codes via phone or mail.

Thanks for the lengthy details and I am sure these suggestions will give them plenty to try for each and all of the issues

best to all and any comments re similar experiences I am sure will help

Super Moderator
26,313 Posts
ok, Have your pal take his time for the DIY Self Test.
It is a lot to go thru, but most of it reflects what is in the Ford Bronco EVTM/PCED...

suggest he buy the OFFICIAL Ford Bronco Electrical and Vacuum Troubleshooting Manual (EVTM), Powertrain Controls and Emission Diagnosis Manual (PCED), Service Manual CD from Steve83 (search for him here and contact him by the e mail function. or E Bay... Best under $25.00 thing you'll ever buy for repairs/ts.. if you have trouble w/da e mail function here; let me know
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