Test B: Pcm Relay

Enter this test only when directed here by other tests. To prevent replacement of good components, check for faults in following components:

• Ignition switch.
• Generator.
• Battery cables, ground straps and voltage regulator.

This test is only intended to diagnose the following components and circuits:

• Harness circuits; VPWR. PWR, GND and PCMR.
• PCM relay.

1. Check VPWR To PCM
   
   Turn ignition off. Disconnect PCM harness connector. Connect jumper wire between PCMR and GND circuits at PCM harness connector. See Fig 1. Turn ignition on. Measure voltage between ground and PCM terminals No. 66, 71 and 97. See Fig 2. If voltage is not greater than 10 volts, go to next step. If voltage is greater than 10 volts, go to step  7.
   Fig 1: Identifying PCM Relay Circuit & Connector Terminals

   Courtesy of FORD MOTOR CO.
   Fig 2: PCM Connector Terminal Identification

   Courtesy of FORD MOTOR CO.
2. Check VPWR Wire From PCM Relay To PCM
   
   Remove PCM relay located in engine compartment junction box. Measure resistance of VPWR circuit (Black/White wire) between PCM harness connector and PCM relay connector. See Fig 1. See CIRCUIT PIN IDENTIFICATION  table. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, repair open in circuit.
   CIRCUIT PIN IDENTIFICATION
   
   

   PCM Pin No.	Wire Color
   4	White/Green
   10	Black
   19	Black
   39	Black/Red
   45	Black/Red
   66	Black/White
   71	Black/White
   96	Black
   97	Black/White
   104	Black

3. Check Power To PCM Relay
   
   Turn ignition off. Turn ignition on. Measure voltage between PWR terminal (Red wire) at PCM relay connector and battery negative terminal. If voltage is greater than 10 volts, go to next step. If voltage is not greater than 10 volts, check 10-amp ENG CONT fuse. If fuse is okay, repair open in circuit.
4. Check Ground To PCM Relay
   
   Turn ignition off. Ensure PCM relay is disconnected. Turn ignition on. Measure voltage between PWR terminal (Red wire) and PCMR terminal (White/Green wire) at PCM relay connector. If voltage is greater than 10 volts, go to step  6. If voltage is not greater than 10 volts, go to next step.
5. Check Continuity Of PCM Relay Circuit
   
   Turn ignition off. Remove PCM relay. Measure resistance of PCMR circuit (White/Green wire) between PCM harness connector and PCM relay harness connector. If resistance is less than 5 ohms, replace PCM. If resistance is not less than 5 ohms, repair open in White/Green wire.
6. Test PCM Relay
   
   Turn ignition off. Apply battery power to PCM relay terminal No. 1, and ground terminal No. 2. See Fig 3. With battery power applied, check continuity between relay terminals No. 3 and 5. If continuity is present, go to next step. If continuity is not present, replace relay.
   Fig 3: Testing PCM Relay

   Courtesy of FORD MOTOR CO.
7. Check Grounds At PCM
   
   Leave ignition off. Disconnected PCM harness connector. Measure resistance of ground circuits between negative battery terminal and PCM connector terminals No. 10, 19, 39, 45, 96 and 104. See WIRING DIAGRAMS article. If all resistance readings are less than 5 ohms, ground circuits are okay. Replace PCM. If any resistance readings are not less 5 ohms, repair open in appropriate ground circuit.