Chart D DERM Cannot Communicate With PDT

CIRCUIT DESCRIPTION
When the Ignition Switch is first turned "On," system voltage is applied from the "IGN 1" fuse to "WLAMPHI," Terminal "B9", and to the "Air Bag" telltale lamp which is connected to "WLAMPLO," Terminal "A1." The "Air Bag" fuse applies system voltage to the "IGN 1" inputs, Terminals "A3" and "B3." The DERM responds by flashing the "Air Bag" telltale lamp seven times.

When the engine is being cranked, system voltage is applied from the "IGN 3" fuse to the DERM at the "Crank" input.

The DERM responds by grounding the "WLAMPLO" output until system voltage is removed from the "Crank" input. This results in the "Air Bag" telltale lamp being "On" during cranking.

After cranking the DERM will again flash the "Air Bag" telltale lamp seven times.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. An improper connection to the Data Link Connector (DLC) will prevent communications from being established.
2. The correct software 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.