The first test is to confirm that the ISCU (identified as "N8") is grounded properly. This is done by removing the ISCU from its perch behind the glove box. This in itself can be a challenge, since there are numerous items in the way. You will need to pull the carpeting out on the passenger side and the under-dash footwell panels. On my car, I have been deleting systems that I no longer desire, such as the climate control ducting and vacuum control pods. I have removed several unused control units, so don't be alarmed by the absence of in-dash equipment in the photos that follow.



I found it easiest to unbolt the bracket that holds the cluster of control boxes behind the glove box, for insertion of the metering probes into the female connectors that are snapped within the bracket. You can separate the individual connectors from the bracket, but it's tough to do from underneath. On previous testing events, I tried to pierce the appropriate wire with my probes, but the wire jackets are nearly plastic-hard on my car. Whatever it takes, just take your time and don't get too aggressive with the pulling and tugging of wiring.



Here I am testing the ISCU's ground by measuring the voltage from the connector's socket number 11 (reading the molded numbers on the connectors is another challenge) to a nearby source of 12 volts. I found an open lug terminal above the fuse box, among the forest of plug-in relays. I measured 12.5 volts. For reference, I also measured the voltage across the battery posts, which was also 12.5 volts (engine is off at this time). The target value is between 11 and 14 volts.