Chart G DERM Cannot Communicate Through the Serial Data Circuit

CIRCUIT DESCRIPTION
When the ignition switch is first turned "ON," system voltage is applied from the GAUGES fuse to "SIR Indicator High," terminal "B9," and to the "AIR BAG" warning lamp which is connected to "SIR Indicator Low," terminal "A1." The AIR BAG fuse applies system voltage to the "Ignition 1" inputs, terminals "A3" and "B3." The DERM responds by flashing the "AIR BAG" warning lamp 7 to 9 times.

When the engine is being cranked, system voltage is applied from the RLC fuse to the DERM at the "Crank" input. The DERM responds by grounding the "SIR Indicator Low" output until system voltage is removed from the "Crank" input. This results in the "AIR BAG" warning lamp being "ON" during cranking.

After cranking, the DERM will again flash the "AIR BAG" warning lamp 7 to 9 times.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. An improper connection to the data link connector will prevent communications from being established.
2. The correct cartridge must be used to communicate with the DERM.
3. This test checks for a short to ground on the "Serial Data" circuit.
4. This test checks for an open in the "Serial Data" circuit.
5. This test checks for a short to B+ on the "Serial Data" circuit.