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 and ground.
• PCM relay.

1. Check VPWR To PCM
   
   Turn ignition off. Disconnect PCM. Connect jumper wire between PCM relay PCMR circuit and PCM terminal No. 4. See Fig 1. Turn ignition on. Measure voltage between ground and PCM terminals No. 66, 71 and 97. See Fig 2. If voltage is less than 10 volts, go to next step. If voltage is greater than 10 volts, go to step  7. If sent here from switch monitor test and voltage is greater than 10 volts, go to next step.
   Fig 1: PCM Connector Terminal Identification

   Courtesy of FORD MOTOR CO.
   Fig 2: Identifying PCM Relay Circuit & Connector Terminals

   Courtesy of FORD MOTOR CO.
   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

2. Check VPWR Wire From PCM Relay To PCM
   
   Remove PCM relay located in engine compartment junction box. Measure resistance between Black/White wire at PCM relay harness connector and PCM connector terminals No. 66, 71 and 97. See Fig 2. Also see CIRCUIT PIN IDENTIFICATION  table. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair VPWR (Black/White) wire.
3. Check Battery Voltage At PCM Relay
   
   Turn ignition off. Remove PCM relay. Turn ignition on. Measure voltage between PWR terminal (Red wire) at PCM relay connector and battery negative terminal. If voltage is 10 volts or greater, go to next step. If voltage is less than 10 volts, check 10-amp ENG CONT fuse. If fuse is okay, repair power distribution circuit.
4. Check PWR Circuit To PCM Relay
   
   Turn ignition off. Ensure PCM is connected. Remove PCM relay located in fuse panel. Turn ignition on. Measure voltage between PWR terminal (Red wire) and ground terminal No. 4 (White/Green wire) at PCM relay connector. If voltage is 10 volts or greater, go to step  6. If voltage is less than 10 volts, go to next step.
5. Check Ground At PCM Relay
   
   Turn ignition off. Remove PCM relay. Measure resistance between PCM connector terminal No. 4 and GND (White/Green wire) terminal at PCM relay. If resistance is less than 5 ohms, replace PCM. If resistance is greater than 5 ohms, repair open in White/Green wire circuit.
6. Test PCM Relay
   
   Turn ignition off. Disconnect PCM relay. 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. Ensure PCM is disconnected. Measure resistance between ground and PCM connector terminals No. 10, 19, 39, 45, 96 and 104. If all resistance measurements are less than 5 ohms, ground circuits are okay. Replace PCM. If any resistance measurement is greater than 5 ohms, repair appropriate ground circuit.