yo,
for the Programmable Speedometer Odometer Module (PSOM);
Check Fuses 8 & 18 in Cab fuse block (lower left of dash by driver's left knee)
If no 12 v on Supply Side of each; look in Power Distribution Box (Located under the hood on the drivers side fenderwell, on driver's side of the air cleaner housing)
and check **** FUSES J & S
Diagram in a 95 from FORD EVTMSource: by Seabronc (Rosie, Fred W) at Ford Bronco Zone Forums
PSOM wiring diagram for 96 Bronco;93-95 similar by Ford via Steve83
This problem could be caused by a # of thangs;
bad vehicle speed sensor (VSS) (also called ABS,, DSS sensor) sensor on da 8.8 (rear differential)/ or
Connector/corroded wires inside connector;
or cruddy/damaged tone ring in the 8.8.
bad wiring/shorts /connectors from VSS at firewall, at 4WABS Module and /or at PSOM and then onto the PCM
bad 4WABS Module - It is located below ws wiper fluid/coolant recovery tank. So, the connector can be corroded by leaking fluid
bad PSOM (Speedo)
My 96's same symptoms were erratic until the 4WABS Module's microprocessors finally burnt-out. I had one go bad and 2 yard Modules were also bad; so I jumpered the Module out as Steve & Turbo Ghost describes below.
To bypass the 4WABS module @ it's harness's connector & feed the ABS signal directly to the PSOM,
Disconnect module (under coolant recovery /ws washer tank) & in connector, jumper LG/Bk to LG/Y, and R/Pk to O/LB..."
Source: by Steve83 (Steve, That dirty old truck) at
http://www.supermotors.net/registry/media/170517_1
Pin numbers are shown in the wiring diagram
or with a pic of the connector and jumpers; Continuity Test Through 4WABS Module Connector in 93-96; "...jumper 14 (CKT 530, LG/Y) to 21 (CKT 519 (LG/BK) & 39 (CKT 491 (O/LB) to 22 (CKT 523, R/PK)...";
Source: by Turbo Ghost at
http://img.photobucket.com/albums/v252/turboghost/ABSConnectorw-jumpers.jpg
Speed Input Signal Test @ PSOM in 93-96 Bronco; "...NOTE: Only wiring harness end of connector is to be probed. * Connect Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to Pin 4 (speed in ) and Pin 5 (speed in -). * Does the voltage increase smoothly and continuously from 0 to approximately 3.5 volts as vehicle speed increases from 0 to 48 km/h (0 to 30 mph)? OR: If available, a frequency counter may be connected to Pin 4 (Speed in ) and Pin 5 (Speed in -). Does the displayed frequency of the signal increase smoothly and continuously from 0 to approximately 667 Hz at approximately 48 km/h (30 mph)? OR: *
If neither a voltmeter nor frequency counter is available, vehicle speed control may be used as a good indicator. If it works normally, then the speedometer module is at least receiving a speed input signal and the wiring and sensor & tone ring can be assumed to be good. This is tuff to do; suggest using str8 pins to back probe the connector
................
For reference purposes:
PSOM Pointer 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..." read more
Source: by Ford via miesk5 @
http://home.comcast.net/~miesk5/tech..._bulletins.htm
This also addresses the tone ring & PSOM unit
EXCERPT; ISSUE: 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.
ACTION: Replace the Programmable Speedometer/Odometer Module (PSOM) if required. New PSOM's come with increased immunity to system variability. Refer to the following Diagnostic Procedure for details.
DIAGNOSTIC PROCEDURE
BRONCO/F-SERIES - Perform normal PSOM diagnostics per Pinpoint Tests "H" and "J" of the 1996 F-Series/Bronco Body/Chassis Service Manual, Pages 13-01-30 through 13-01-32 and Pinpoint "B" of the 1996 Powertrain/Drivetrain Service Manual, Page 10-03-11.
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
============
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 FSB
more VSS info in my site @
http://www.broncolinks.com/index.php?index=139
-
More 4WABS Info, Connector Location and pin out diagrams etc in my site @
http://www.broncolinks.com/index.php?index=240
= ================
PSOM & Odometer Not Working & E4OD Harsh Shift TSB 94-09-12 for 94 Bronco & F Series; "...PSOM (Programmable Speedometer/Odometer Module) may be inoperative or not function properly and the #8 fuse may be blown. In addition, if the vehicle is equipped with an E4OD 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..." Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net
Odometer & Keyless Entry Inoperative; Fuse 8 Overload, Possible Short In Circuit 54 TSB 95-14-11 for 94-95 Bronco & F Series; also affected Inoperative Courtesy, Map, Engine & Glove Compartment, Dome, Vanity, & Cargo Lamps & Inoperative Power Mirrors Source: by Ford via thedieselstop.com
ISSUE: Some customers may have concerns that the following features are inoperative:
* All courtesy lamps
* Map lamps
* Engine compartment lamp
* Glove compartment lamp
* Odometer in the instrument cluster
* Dome lamp
* Power mirrors
* Lighted vanity
* Cargo lamp
* Remote keyless entry
This is due to insufficient clearance between the outer roof panel of the cab and a map/dome lamp mounting ****** causing a short in Circuit 54, which causes Fuse 8 (15 amp) to become inoperative. This fuse protects the wiring for the above vehicle features.
ACTION: Replace existing dome mounting screws with new, shorter screws. Refer to the following procedure for service details
=====
Turn Signals are powered by Fuse 7 in cab (and it also powers the rear window defroster ckt) and it is is powered by **** Fuse N in PDB, so I don't see a relation between the PSOM & Turn signals wiriing or a short that would blow da fuse
check harness for short(s) near turn signal lamp as show here;
Turn Signal, Front Harness Chaffing & Repair Video in a 94 Source: by pfun41 at youtube.com
suggest right clicking Hot Link and open in a new window
====================
DTC 27, 29,
452, P0502, P0503, PO716, PO718; Insufficient input from VSS.; "...A more difficult problem to identify is a VSS that works, but sends out the wrong signal for a given vehicle speed. In some cases, a wrong reading from the VSS may still cause a code to be set. For example, if the VSS signal tells the computer the vehicle is traveling 60 miles an hour, but the throttle position sensor and MAP sensor tell the computer that the engine is idling, the computer will be confused. And a confused computer should set any of the following codes: Ford 27, 29, 452. On a vehicle that uses the VSS as a safety device, a defective sensor may send out a wrong "too fast" signal, shutting down fuel flow at the wrong time. Although this doesn’t happen often, it can be a difficult problem to identify. The customer will probably describe it as a random or intermittent sudden loss of power and poor performance, onlyto have the engine resume normal operation. Routine diagnostic checks of the engine in the shop won’t show any problem because there isn’t a problem with the engine or the ECM..." read more
Source: by wellsmfgcorp.com
..
DS1 DIAGNOSTIC TROUBLE
CODES (DTCS) 29 AND
452: CHECK PSOM RESISTANCE
Follow this procedure EXACTLY, from the Ford TSP/PCED:
iggie this unless you have or know someone that has the Ford Break-Out Box
and use your Multi Meter for the same R tests on the VSS Sensor (called RABS here) shown above
Continuous Memory DTC 29 indicates that during the last 80 warm-up cycles, the PCM detected an error in the PSOM output signal.
DTC 452 indicates the PCM detected an error in the PSOM output signal during the last 40 warm-up cycles.
Possible Causes:
Damaged Rear Anti-Lock Brake System (RABS).
Damaged PSOM.
Damaged harness circuits.
Damaged PCM.
l Key off.
Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Install breakout box, leave PCM disconnected. (Measure resistance between Test Pin 3 and Test Pin 6 at the breakout box.
Is resistance between 21,000 and 55,000 ohms?
Yes
GO to «DS4».
No
GO to «DS2».
Quote:
DS2 CHECK CONTINUITY OF THE HARNESS CIRCUITS
Key off.
Breakout box installed, PCM disconnected.
Disconnect PSOM.
Measure resistance between Test Pin 3 at the breakout box and PSOM(+) circuit at the PSOM vehicle harness connector.
Measure resistance between Test Pin 6 at the breakout box and PSOM(-) circuit at the PSOM vehicle harness connector.
l Is each resistance less than 5.0 ohms?
Yes
GO to «DS3».
No
SERVICE open circuit. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
Quote:
DS3 CHECK HARNESS CIRCUITS FOR SHORTS TO POWER AND GROUND
Key off.
Breakout box installed, PCM disconnected.
PSOM disconnected.
Measure resistance between Test Pin 3 and Test Pins 6, 37 and 40 at the breakout box.
Is each resistance greater than 10,000 ohms?
Yes
GO to «DS4».
No
SERVICE short circuit. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
Quote:
DS4 CHECK RABS SENSOR RESISTANCE
Key off.
RABS disconnected.
Measure the resistance of the RABS.
Is resistance between 1300 and 1550 ohms?
Yes
GO to «DS5».
No
REPLACE the RABS. REMOVE breakout box. RECONNECT all components. RERUN «Quick Test».
Quote:
DS5 CHECK PSOM OUTPUT VOLTAGE
WARNING:
THIS TEST STEP REQUIRES ANOTHER PERSON TO ACCOMPANY THE DRIVER TO MAKE MEASUREMENTS AND RECORD DATA. ALL APPLICABLE SAFETY PROCEDURES AND TRAFFIC LAWS MUST BE FOLLOWED.
Key off.
Breakout box installed.
Reconnect PCM to breakout box.
Reconnect PSOM.
DVOM on 20 volt AC scale.
Warm engine to operating temperature.
Measure AC voltage between Test Pin 3 and Test Pin 6 while gradually increasing vehicle speed to 50 mph.
Is the maximum voltage received greater than 4.0 volts?
Yes
REPLACE PCM. REMOVE breakout box. RERUN «Quick Test».
No
REMOVE breakout box. RECONNECT components. REFER to the Instrument Cluster, Speed Control or Brake Group in the Service Manual for further diagnosis.
by SigEpBlue
=======
DTC 311 Thermactor air system inoperable. "...The computer determined that for some reason the fresh air injection from the Thermactor system was not present. There are several components that make up this system. The initial component is the smog pump. The first checks I would make are the hoses and plumbing from the smog pump back to the diverter valve (behind the pass. cylinder head) and then on to the crossover pipe at the back of the heads and down to the catalytic converter. The check valves that are at the center of the cross over pipe and the top of the metal tube from the cat are often the culprits as they can and do snap in half as the get old. If the plumbing looks to be in good order we can discuss the slightly more complicated aspects of the system. The diverter valve also has two vacuum lines running to it. Make certain they are in place and intact. (Computer needs to be able to control the flow of fresh air by the Thermactor system)..."
Source: by greystreak92
DTC 332 - Insufficient EGR flow detected. "...Atop the EGR valve there is a sensor called the EVP (EGR Valve Position) sensor. It detects movement of the pintle iside the EGR valve. You can apply vacuum to the vacuum barb on the EGR valve and observe through the holes in the casting whether the valve is moving or not. It may just be dirty which requires some careful scrubbing and NO SOLVENTS. Otherwise, if the EGR valve is functioning and moving when vacuum is applied, the EVP sensor is suspect and the electrical connections to it should be checked first. (Computer needs to know the EGR valve position for emissions control)..."
Source: by greystreak92
DTC 332, P1407 and P1408 or detonation; "...We have run into many situations where a code for insufficient flow has been set and the system is functioning correctly. Then it is time to check the EGR passages. There is a Ford Technical Service Bulletin (TSB 96-23-4) that addresses this for some vehicles. This TSB includes: 1992-1995 Crown Victoria 1994-1995 Thunderbird 1991-1995 Town Car 1992-1995 Grand Marquis 1994-1995 Cougar The concerns have to do with intermittent MILs; DTCs 332, P1407 and P1408; or detonation. If exercising the EGR valve does not result in a change in rpm, then the passages may be clogged. There are “U” shaped passages (Fig. 6) under the throttle body adapter that get clogged with carbon. Remove the adapter, clean the passages and reinstall with a new gasket. Just because the vehicle you are working on is not listed in the TSB doesn’t mean you may not have a clogging problem. Make sure you check the passages and be sure they are clean. Just a slight restriction can cause a flow code to be set, and you may still have an rpm drop that can mislead you..." Source: by tomco-inc.com
DTC 332 in a 95; "...CHECK YOUR VACUUM CANISTER; I had this issue for well over a year. I did all my proper checks using the blueprint that Meisk5 gave me. I went through the EVP, manually checked the EGR, all vacuum hose that was pertinent, ETC. removed my vacuum canister to install my new one and this is what I found underneath. I replaced it with this canister (rust bullet applied) from my donor truck and finished it with BlackShell..."
Source: by td 152
