Diagnostic Aids

WARNING: This page is about a different car, the 1995 Ford Windstar and 1995 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.

Delayed engagement of transmission may be caused by mechanical malfunction. Harsh shifts and/or erratic speedometer reading may be caused by a failed speedometer or an open or intermittent ground within the instrument panel (electronic instrument cluster). Perform this test when directed by QUICK TEST. This CIRCUIT TEST is intended to diagnose:

* Vehicle Speed Sensor (VSS).

* VSS wiring harness circuits. (SIG RTN, VSS+ and VSS-).

* Powertrain Control Module (PCM).

Fig 1: Identifying VSS Circuit & Connector Terminals

TEST PIN NO. 33 (VSS -) WIRE COLOR IDENTIFICATION

Application	Wire Color
Ranger	Pink/Orange
Windstar	Orange/Yellow

TEST PIN NO. 58 (VSS +) WIRE COLOR IDENTIFICATION

Application	Wire Color
Ranger	Gray/Black
Windstar	Dark Green/White

1) DTC P0500

This code indicates PCM detected incorrect output from VSS sometime during vehicle operation. Possible causes for this code are:

* Faulty VSS.

* Open or shorted circuit.

* Faulty PCM.

Turn ignition off. Disconnect VSS sensor. Remove PCM 104-pin connector. Inspect connector for damaged pins, corrosion and loose wires. Repair as necessary. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Measure resistance between test pin No. 33 and VSS(-) terminal at VSS wiring harness connector. Measure resistance between test pin No. 58 and VSS(+) terminal at VSS wiring harness connector. If both resistance readings are less than 5 ohms, go to next step. If either resistance reading is 5 ohms or more, repair open circuit in VSS wiring harness. Clear PCM memory and go to step 20).

2) Check VSS Circuits For Shorts To Power Or Ground

Turn ignition off. Ensure PCM and VSS are disconnected. Measure resistance between test pin No. 33 and test pin No. 71. Measure resistance between test pin No. 58 and test pins No. 51, 103 (PWR GND), 33, 71 (VPWR), and 91 (SIG RTN) at breakout box. If all readings are more than 500 ohms, go to next step. If any reading is less than 500 ohms, repair shorts in VSS wiring harness. Clear PCM memory and go to step 20).

3) Check VSS Resistance

Turn ignition off. Disconnect VSS wiring harness connector. Measure resistance between VSS terminals. If resistance is not 190-250 ohms, replace VSS and go to step 20). If resistance is 190-250 ohms, replace PCM and go to step 20).

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 3) to step 10). No test procedures have been omitted.

10) DTC P1500

This code indicates PCM detected intermittent input from VSS. Possible causes for this code are:

* Intermittent open or shorted circuit.

* Faulty VSS.

* Faulty PCM.

Turn ignition off. Disconnect VSS sensor. Visually inspect VSS and VSS circuits for potential faults as follows:

* Loose VSS circuit connectors.

* Loose VSS circuit connector pins.

* Damaged VSS wiring harness insulation.

* Incorrect VSS circuit routing.

* Incorrect VSS installation.

If no faults are found, go to CIRCUIT TEST Z. If faults are found, repair or replace as necessary. Clear PCM memory and go to step 20).

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 10) to step 20). No test procedures have been omitted.

20) VSS Drive Cycle

Record and clear continuous memory codes. Warm engine to normal operating temperature. Perform appropriate drive cycle as follows:

* On models with A/T, place gear selector in Drive position. Accelerate hard to 35 MPH and coast down to a stop. Repeat procedure 3 times. Shut off engine. Repeat QUICK TEST. Service codes as necessary. If no codes are present, testing is complete.

On models with M/T, start in first gear, shifting no higher than second gear. Accelerate moderately to 40 MPH. Coast down to idle, and stop. Repeat procedure 3 times. Shut engine off. Repeat QUICK TEST. Service codes as necessary. If no codes are present, testing is complete.