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.

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used to diagnose the following:

Standard Corporate Protocol (SCP) communication circuits BUS (+) and BUS (-).
Wiring harness circuits (CHASSIS GROUND, PWR GND and VBAT).
Faulty Powertrain Control Module (PCM).

Fig 1: DLC Test Circuit & Connector Terminal ID (Ranger & Windstar)

1) Verify Self-Test Procedure Is Correct

Ensure scan tester is correctly attached to DLC located under dash panel. DO NOT use DLC located in engine compartment. Ensure correct self-test procedure is used. Correct as necessary. If correct procedures were used, go to next step.

2) Check For VREF At TP Sensor

Turn ignition off. Disconnect TP sensor. Turn ignition on. Measure voltage between SIG RTN terminal and VREF terminal at TP wiring harness connector. See Fig 2 . If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to CIRCUIT TEST C.

NOTE: KOER self-test failure or Communication Error message could result if a failure is present in MAF sensor, MLP sensor, VSS or related circuits.

Fig 2: TP Sensor Harness Connector Terminal ID (Ranger & Windstar)

3) Ability To Access Continuous Memory DTCs

If Continuous Memory DTCs were accessible, go to next step. If Continuous Memory DTCs were not accessible, go to step 8).

4) Ability To Activate KOEO Self-Test

If KOEO self-test was entered, go to next step. If KOEO self-test was not entered, go to step 8).

5) Ability To Activate KOER Self-Test

If KOER self-test was entered, DTC is false. Obtain PCM part number and check manufacturer for correct PCM application. If KOER self-test was not entered, go to next step.

6) Check Engine Idle Speed

KOER self-test cannot be entered if engine speed is too high or too low. Turn ignition off. Ensure all accessories are off. Connect scan tester to Data Link Connector (DLC). Turn ignition on. Using scan tester, access RPM PID. Check engine idle speed. If idle speed is okay, go to next step. If idle speed is not okay, go to CIRCUIT TEST HU.

7) Perform QUICK TEST. If any trouble codes are present, service as necessary before continuing. If unable to retrieve trouble codes, go to next step.

8) Check For Voltage At Data Link Connector (DLC)

Inspect DLC for damage and repair as necessary. Turn ignition on. Measure voltage between B+ terminal of DLC and engine ground. If 10.5 volts or more are present, go to next step. If less than 10.5 volts are present, repair open in B+ circuit and repeat QUICK TEST.

9) Check DLC Ground Circuit Continuity

Turn ignition off. Measure resistance between CHASSIS GROUND terminal of DLC and engine ground. If less than 5 ohms are present, go to next step. If 5 ohms or more are present, repair open in CHASSIS GROUND circuit and repeat QUICK TEST.

10) Turn ignition off. Disconnect PCM 104-pin connector. Inspect pins for damage and repair if necessary. Install EEC-V Breakout Box (014-00950), leaving PCM disconnected. Measure resistance between test pins No. 51 and 103 (PWR GND) at the breakout box and PWR GND terminal of DLC. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in PWR GND circuit to DLC and repeat QUICK TEST.

11) Check BUS(-) Circuit

Leave ignition off. Measure resistance between test pin No. 15 (BUS-) at the breakout box and BUS(-) terminal of DLC. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in BUS(-) circuit to DLC and repeat QUICK TEST.

12) Leave ignition off. Measure resistance between test pin No. 15 at the breakout box and engine ground. If resistance is 10,000 ohms or more, go to next step. If resistance is less than 10,000 ohms, repair short to ground in BUS(-) circuit and repeat QUICK TEST.

13) Turn ignition on. Measure voltage between test pin No. 15 and test pins No. 51 and 103 (PWR GND) at the breakout box and engine ground. If voltage is less than 1.0 volt, go to next step. If voltage is 1.0 volt or more, repair short to power in BUS(-) circuit and repeat QUICK TEST.

14) Check BUS(+) Circuit

Leave ignition off. Measure resistance between test pin No. 16 (BUS+) at the breakout box and BUS(+) terminal of DLC. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in BUS(+) circuit to DLC and repeat QUICK TEST.

15) Turn ignition on. Measure voltage between engine ground and test pins No. 16, 51 and 103 (PWR GND) at the breakout box. If voltage is less than 1.0 volt, replace PCM. If voltage is 1.0 volt or more, repair short to power in BUS(+) circuit and repeat QUICK TEST.