Paraphrase of testing procedure for normal home use:
1) With engine running, measure voltage between SPOUT at ignition module and battery negative. >2 volts go to step 2, else go to step 6.
2) Check for spark at each left side plug wire with engine running. If spark exists on at least 1 wire, replace ignition module and run codes again. Else go to step 3.
3) Turn ignition off and disconnect wiring harness to computer (drivers side against the firewall). Measure between DPI pin at computer harness and DPI pin at ignition module harness. If < 5 ohms, go to step 4. If not, there is a break in the DPI wire between the ignition module and computer. Locate and repair, then run codes again.
4) Turn ignition on and measure voltage between DPI pin at ignition module and battery negative. If < .5 volts, go to step 5. If not, DPI wire is shorting to ground. Locate and repair, then run codes again.
5) Reconnect computer wiring harness. Connect a test light between DPI pin at ignition module and battery ground. Start engine. If light is on, replace engine computer and run codes again.. If off, replace ignition module and run codes again.
6) Turn ignition off. Set volt meter to AC, then measure voltage between SPOUT connector at ignition module and battery ground while cranking engine. If > .1 volt, replace ignition module and run codes again. Else go to step 7.
7) Turn ignition off. Set volt meter back to DC and disconnect wiring harness to computer. Turn ignition on. Measure voltage between SPOUT connector at ignition module and battery ground. If > .5 volts DC, SPOUT wire is shorting to power between computer and ignition module - locate, repair, and run codes again. If .5 volts or less, replace engine computer.