Chart B Flash Code Diagnosis

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" steady 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. This test determines whether "Flash Code" diagnostics can be enabled.
2. This test checks for a good ground at the data link connector.
3. This test checks for an open in the "Diagnostic Request" circuit.
4. This test checks for a short to B+ in the "Diagnostic Request" circuit.
5. This test determines whether further diagnosis is required.
6. This test determines whether only history or both current and history diagnostic trouble codes exist.