I've had some shifting problems come up on my 94 F150 lately. I've checked just about everything mechanical I can think of and can't find the problem. I'm convinced it is an electrical fault and need some help.

Symptoms are rough shift, especially between 1st and 2nd, seeming to slip in and out of gear when in 3rd and overdrive. Problem is intermittent, but is getting worse. When it starts to do this, the cruise control will stop working. I've pulled the codes and get a 452- VSS voltage too small- when this happens. I've replaced the VSS as well as the MLPS and put new replacement harnesses on both transmission wiring connectors. Speedo seems to be working fine, no jumping, rock steady. I've checked the wiring and connector going to the VSS and it checks out fine. Seems to be pointing to a problem with the PSOM. Found this service advisory while doing some research on the problem.


Programmable Speedometer/Odometer Module- Pointer Waver-Service Tip
Article Number 96-21-11

LIGHT TRUCK:
1992-96 AEROSTAR, BRONCO, ECONOLINE, F-150-350 SERIES

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.

ECONOLINE - Perform normal PSOM diagnostics per Pinpoint Tests "H" and "J" of the 1996 Econoline Body/Chassis Service Manual, Pages 13-01-29 through 13-01-31 and Pinpoint "B" of the 1996 Powertrain/Drivetrain Service Manual, Page 10-03-9.

AEROSTAR - Perform normal PSOM diagnostics per Pinpoint Test "K" of the 1994 Aerostar Body/Chassis Service Manual, Page 13-01B-31.

1. 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").

2. 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.

3. 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.

NOTE:
DEALERSHIP MUST TELL THE ODOMETER EXCHANGE CENTER THAT YOU NEED A PSOM3 LEVEL CLUSTER FOR A SPEEDOMETER NEEDLE WAVER CONCERN.

OTHER APPLICABLE ARTICLES: NONE

WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage

LABOR ALLOWANCE

DEALER CODING

OASIS CODES: 204000, 204100, 204200, 205000

Can anybody help me with the diagnostic procedure they are talking about? Don't have access to the service manual so I need to know what these "pinpoint" tests they refer to are. This thing is driving me crazy, any help would be greatly appreciated.






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Tests out of the 96 manual.

H tests;

Pinpoint Tests

PINPOINT TEST H: SPEEDOMETER, IMPROPER OPERATION


H1 CHECK SPEEDOMETER OPERATION


l Is speedometer free from hesitation or sticking when accelerating or decelerating smoothly? This may be confirmed by performing the following test:

-- Press and hold the RESET button on the front of the speedometer while turning the key to RUN.

-- Release the RESET button.

l Does the pointer smoothly prove out, or sweep from 0 to maximum speed then back to 0?

yes got to H2

No
After verifying good power and ground connections, GO to «G6». REPLACE instrument cluster . VERIFY proper operation.


Pinpoint Tests

PINPOINT TEST H: SPEEDOMETER, IMPROPER OPERATION


H2 CHECK ODOMETER DISPLAY


l The trip odometer must be currently displayed for the RESET button to work.

l If unsure about missing or extra segments, perform the odometer display self test as follows:

-- Press and hold the reset button on the front of the speedometer while turning the key to RUN.

-- Release the RESET button.

-- Press and release the select button. The odometer will begin with all zeroes and step through the display test each time the select button is pushed. Refer to PSOM Display Test Sequence below for exact display.

l The first digit on the left does not always match the other digits.

-- Key off to exit this test.



l Are all odometer digits formed correctly (no extra or missing segments)? Do the select and reset buttons work normally?

Yes
GO to «H3». CHECK pointer.

No
REPLACE instrument cluster . VERIFY proper operation.

Pinpoint Tests

PINPOINT TEST H: SPEEDOMETER, IMPROPER OPERATION


H3 CHECK SPEEDOMETER POINTER


l Does pointer jump or waver at a constant speed?

Yes
GO to «H4».

No
GO to «H5»

Pinpoint Tests

PINPOINT TEST H: SPEEDOMETER, IMPROPER OPERATION


H4 CHECK RABS SPEED SENSOR RING AND SENSOR


l Check for presence of the following conditions.

-- Damaged, missing or bent teeth

-- Metal chips on speed sensor

-- Open or shorted sensor

-- Improper gap between sensor and speed sensor ring

l Refer to «Section 06-09A» for additional information.

l Are any of the above conditions present?

Yes
REPAIR or REPLACE as necessary. VERIFY proper operation.

No
REPLACE the instrument cluster . VERIFY proper operation.

Pinpoint Tests

PINPOINT TEST H: SPEEDOMETER, IMPROPER OPERATION


H5 CHECK FOR STUCK POINTER


l Is pointer stuck at upper pointer stop?

Yes
GO to «H6».

No
Speedometer normal.

Pinpoint Tests

PINPOINT TEST H: SPEEDOMETER, IMPROPER OPERATION


H6 SPEEDOMETER POINTER PROVEOUT


l Press and hold the RESET button on the front of the speedometer while turning the key to RUN.

l Release the RESET button. The pointer would normally prove out, or sweep from the lower to upper pointer stop and back again. In this case, the pointer will "jump back" to where it should be in the sweep and continue to sweep normally when the pointer gets to within 180 degrees of the upper pointer stop (about 56 km/h [35 mph]).

l Key off.

l Does the pointer return to the normal position?

Yes
Speedometer normal.

No
REPLACE the instrument cluster . VERIFY proper operation.



Pinpoint Tests

PINPOINT TEST J: SPEED CONTROL, PCM OR ELECTRONIC TRANSMISSION DISPLAY INOPERATIVE OR ERRATIC


J1 CHECK ANTI-LOCK LAMP ILLUMINATION


l Key to RUN.

l Does anti-lock lamp on dash go out after self-test?

Yes
GO to «J2».

No
REFER to «Section 06-09A» or «Section 06-09B».


Pinpoint Tests

PINPOINT TEST J: SPEED CONTROL, PCM OR ELECTRONIC TRANSMISSION DISPLAY INOPERATIVE OR ERRATIC


J2 CHECK SPEEDOMETER SPEED OUTPUT SIGNAL


CAUTION: Before checking the continuity of any circuit, make sure there is no voltage present in the circuit prior to switching the test equipment to the resistance function to avoid damage to equipment. Refer to the test equipment user's manual for additional information.

l To determine if there is a short between the PSOM and the speed control module, the vehicle speed control may be used as a good indicator. If it works normally above 56 km/h (35 mph), this means that the speedometer module is at least receiving a speed input signal and the wiring and sensor can be assumed to be good.

Note: Only wiring harness end of connector is to be probed.

l Use ohmmeter to check for opens in wiring between Pin 7 (speed out) and the affected module. Verify that the terminals in PSOM wiring connector are completely seated in the connector.

l Is the circuit open?

Yes
SERVICE wiring between speedometer and affected module as required. VERIFY proper operation.

No
GO to «J3».


Pinpoint Tests

PINPOINT TEST J: SPEED CONTROL, PCM OR ELECTRONIC TRANSMISSION DISPLAY INOPERATIVE OR ERRATIC


J3 CHECK SPEED INPUT SIGNAL


CAUTION: Make sure multimeter is in the voltage function and not in the resistance function to avoid damage to multimeter.

Note: Only wiring harness end of connector is to be probed.

l Connect Rotunda 88 Digital Multimeter 105-00053 or equivalent to Pin 4 (speed +) and Pin 5 (speed -).

l If available, a frequency counter may be connected to Pin 4 (speed in +) and Pin 5 (speed in -).

l 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 does the voltage increase smoothly and continuously from 0 to approximately 3.5 volts as vehicle speed increases from 0 to approximately 48 km/h (30 mph)?

Yes
REPLACE instrument cluster .

No
SERVICE wiring. CHECK for open wiring. If no problems are found, REFER to «Section 06-09A» or «Section 06-09B».

 

Thanks Dave, just what I needed!