Diagnostic Aids

WARNING: This page is about a different car, the 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:

Wiring harness circuits (B+, FC, POWER-TO-FAN and VPWR).
Faulty fan control relay.
Faulty Powertrain Control Module (PCM).

Fig 1: Fan Control Relay Test Circuit & Connector Terminal ID (Ranger)

1) DTC P1474: Check VPWR Circuit

Disconnect fan control relay wiring harness connector. Turn ignition on. Measure voltage between VPWR terminal of connector and negative battery terminal. If voltage is less than 10.5 volts, repair open in VPWR circuit to fan control relay and repeat QUICK TEST . If voltage is 10.5 volts or more, go to next step.

2) Turn ignition off. Leave fan control relay disconnected. Connect scan tester to Data Link Connector (DLC). Turn ignition on. Using scan tester, access Output Test Mode (OTM). Connect positive lead of DVOM to VPWR terminal of relay connector. Connect negative lead to FC terminal. While observing DVOM, command cooling fan on and off. If voltage changes 0.5 volt or more as cooling fan is commanded on and off, replace fan control relay and repeat QUICK TEST . If voltage does not change as specified, go to next step.

3) Check FC Circuit

Turn ignition off. Leave fan control relay disconnected. Disconnect PCM wiring harness connector. Inspect connector for damage or corrosion, and repair as necessary. Turn ignition on. Measure voltage between FC terminal of connector and negative battery terminal. If voltage is one volt or more, repair FC circuit short to power and repeat QUICK TEST . If voltage is less than one volt, go to next step.

4) Turn ignition off. Leave fan control relay disconnected. Install EEC-V Breakout Box (014-000950), leaving PCM disconnected. Measure resistance between test pin No. 28 (FC) and test pins No. 51 and 103 (PWR GND) at breakout box. If resistance is more than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, repair circuit short to ground and repeat QUICK TEST .

5) Check FC Circuit Continuity

Leave ignition off and relay disconnected. Measure resistance between breakout box test pin No. 28 and FC terminal at fan control relay connector. If resistance is 5 ohms or more, repair open in FC circuit and repeat QUICK TEST . If resistance is less than 5 ohms, replace PCM and repeat QUICK TEST.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 5) to step 30). No test procedures have been omitted.

30) Continuous Memory DTC P1474

Turn ignition off. Connect scan tester to Data Link Connector (DLC). Turn ignition on. Using scan tester, access LFCA PID. Scan tester should show LFCA PID off. Observe LFCA PID for indication of fault while wiggling and bending FC circuit between fan control relay and PCM. Fault will be indicated by LFCA PID turning on. Wiggle and bend VPWR circuit between EEC-V power relay and fan control relay. Lightly tap on fan control relay. Check connectors for clean tight connection. If any faults are found, isolate and repair as necessary. If no faults are found, go to next step.

31) Disconnect fan control relay. LFCA PID should be on. Observe LFCA PID for indication of fault while wiggling and bending FC circuit between fan control relay and PCM. Fault will be indicated by LFCA PID turning off. If any faults are found, repair as necessary. If no faults are found, fault cannot be duplicated at this time. Go to CIRCUIT TEST Z.