Chart G - DERM Cannot Communicate With Scan Tool: Description
When ignition is first turned on, system voltage is applied from fuse No. 6 to SIR INDICATOR HIGH and INFLATABLE RESTRAINT indicator light, which is connected to SIR INDICATOR LOW. Fuse No. 7 applies system voltage to IGNITION 1 inputs A3 and B3. Diagnostic Energy Reserve Module (DERM) responds by flashing INFLATABLE RESTRAINT indicator 7-9 times.
When engine is being cranked, system voltage is applied to DERM at CRANK input. DERM grounds light circuit until system voltage is removed from CRANK input. This results in a steady INFLATABLE RESTRAINT indicator during cranking. After engine is cranked, DERM will again flash INFLATABLE RESTRAINT indicator 7-9 times if ignition is on.
NOTE:
Test numbers refer to numbers on diagnostic chart. For circuit number identification, see WIRING DIAGRAMS.
WARNING:
To avoid air bag deployment while trouble shooting SIR system, only use test equipment specified in diagnostic charts. Under no circumstances should battery powered test equipment or test light be used. Carefully follow all instructions.
- An improper connection to Data Link Connector (DLC) will prevent communications from being established.
- Correct Scan tester software cartridge must be used.
- Test checks for short to ground or voltage on serial data circuit.
- Checks for short to ground on serial data circuit between DERM and DLC.
- Checks for open in serial data circuit between DERM and DLC.
- Checks for short to voltage on serial data circuit between DERM and DLC.
- Checks for poor terminal connections in serial data circuit between DERM and DLC.