Vehicle Battery

Fig 1: Power Relay Circuit & Connector Identification

Courtesy of FORD MOTOR CO.

VPWR CIRCUIT PIN IDENTIFICATION

Circuit	ECA Pin	BOB Pin	Wire Color
VREF	2K	26	Bk/W
SIGRTN	2D	46, 49	Bk

NOTE: Enter this test only when directed here from CIRCUIT TESTS. To prevent replacement of good components, note that the following non-EEC components may be faulty: ignition switch, alternator, battery cables, ground straps or voltage regulator. This test is intended to diagnose only the following: ECA, wiring harness circuits, and battery voltage.

1) Checking Battery Circuit Integrity Visually check all wiring, harnesses, connectors and components for evidence of damage, overheating, shorting or looseness. If a fault is found, repair as necessary.

2) Check Battery Charge If no faults are found, check battery voltage and charge condition. Service if necessary and go to next step.

3) Power Check Turn ignition off and install breakout box. Turn ignition on. Measure voltage between the followings points:

VPWR test pin and battery ground
VPWR test pin and each ground test pin
VPWR test pin and each ECA ground wire.

If all voltages are greater than 10 volts, go to CIRCUIT TEST A7. If all voltages are not greater than 10 volts, repair ECA ground circuit.

4) Checking Relay Ground Circuit Turn ignition off. Locate main power relay inside rectangular cover behind master cylinder reservoir. Disconnect main power relay 4-wire connector. Using jumper wire, attach BATT, PWR, and GND terminals to connector. Leave VPWR wire disconnected.

5) Turn ignition on. Measure voltage between main power relay VPWR terminal and ground. If voltage is more than 10 volts, repair VPWR circuit between main power relay and ECA. If voltage is not more than 10 volts, measure voltage between main power relay BATT wire and ground.

6) If voltage is less than 10 volts, repair BATT circuit between main power relay and battery. If there are more than 10 volts, measure voltage between main power relay PWR wire and ground. If voltage is less than 10 volts, repair PWR circuit between main power relay and ignition switch.

7) If voltage is not less than 10 volts, measure voltage between main power relay BATT wire and main power relay ground. If voltage is less than 10 volts, repair main power relay ground wire. If voltage is not less than 10 volts, ground circuit is okay. Replace main power relay.