Test FC - Vehicle Power
To prevent replacement of good components, check ignition switch, fuses, battery and charging system. Inspect wiring, wiring harness, connectors and other related components for visible damage.
- Check For VPWR To ECA: Install breakout box. Unplug ECA and turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 37 and 40 (ground). If reading is 10 volts or less, proceed to step 4). If reading is greater than 10 volts, proceed to next step.
- Check For Cranking Power To ECA: Install breakout box. Unplug ECA and turn ignition on. Using DVOM on 20-volt scale, measure voltage between pins No. 5 and 40 (ground) while cranking engine. If reading is greater than 10 volts, proceed to next step. If reading is 10 volts or less, repair open circuit between ECA terminal No. 3B and starter (Black/Red wire). If circuit is okay, diagnose battery and charging system.
- Check For ECA Grounds: Install breakout box and unplug ECA. Using DVOM on 200-ohm scale, measure resistance between ground pins No. 20, 40, and 49, and chassis ground. If reading is greater than 5 ohms, repair open in wiring harness between ground terminal in question and chassis ground. If reading is 5 ohms or less, proceed to TEST B .
- Check Power At Relay: Turn ignition on. Using DVOM on 20 volt scale, measure voltage at power relay White/Green wire terminal on vehicles built after 11/2/87. Also measure voltage at power relay No. 1 (Yellow/Green wire) and power relay No. 2 (Black/- White wire) on vehicles built before 11/2/87. If all readings are greater than 10 volts, proceed to next step. If all readings are 10 volts or less, check wire(s) for opens or shorts.
- Check Power To Relay: Turn ignition on. Using DVOM on 20 volt scale, measure voltage at power relay Blue and Black wire terminals on vehicles built after 11/2/87. Also measure voltage at power relay No. 1 (Blue/White wire), power relay No. 2 (Blue wire) and power relays No. 1 and 2 (Black/White wire) on vehicles built before 11/2/87. If readings are greater than 10 volts, proceed to next step. If readings are 10 volts or less, check wire(s) for opens or shorts.
- Check Ground At Relay: Unplug power relay. Using DVOM on 200-ohm scale, measure resistance between power relay(s) connector (Black terminal) and ground. If reading is less than 5 ohms, proceed to next step. If reading is 5 ohms or more, repair open in wiring harness between power relay(s) Black terminal and ground.
- Power Relay Operation Check: Unplug power relay and ground Black terminal. Using DVOM on 200-ohm scale, measure the resistance between Blue and Black/White wire terminals, and Blue and White/Green wire terminals. On vehicles built after 11/2/87, jumper battery voltage to power relay Black/White wire terminal. Measure resistance between relay No. 1, Black/White and Yellow/Green wires, relay No. 2, Blue and Black/White wires, relay No. 1, Black/White and Black wires, and relay No. 2, Black/White and Black wires. On vehicles built before 11/2/87, jumper battery voltage to power relay(s) (Black/White wire). If reading is less than 5 ohms with voltage applied and greater than 10,000 ohms with voltage removed, proceed to TEST B. If reading is 5 ohms or more with voltage applied and 10,000 ohms or less with voltage removed, replace power relay(s).