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 Fuse 17 to "SIR Indicator High," terminal "B9," and to the "INFL REST" warning lamp which is connected to "SIR Indicator Low," terminal "A1." Fuse 12 applies system voltage to the "Ignition 1" inputs, terminals "A3" and "B3." The DERM responds by flashing the "INFL REST" warning lamp 7 to 9 times.

When the engine is being cranked, system voltage is applied from Fuse 20 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 "INFL REST" warning lamp being "ON" during cranking.

After cranking the DERM will again flash the "INFL REST" 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 "Body Systems" cartridge must be used.
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.