System Diagnosis - Ignition System

CIRCUIT DESCRIPTION
The IC module determines crankshaft and camshaft position and fires the appropriate spark plug. The IC module also creates 4X and 24X reference pulses that are supplied to the PCM. The PCM uses these reference circuits to determine fuel delivery and spark timing. Most failures in the Ignition Control system will set a PCM DTC. Always perform the Powertrain OBD System Check and, if necessary, the Engine Cranks but Does Not Run diagnostic table BEFORE performing any Ignition System diagnosis. Testing and Inspection

TEST DESCRIPTION
3. The Engine Cranks but Does Not Run table must be performed BEFORE using this diagnostic procedure.
4. Observe the Engine Speed parameter on the scan tool while increasing spark RETARD by 10 degrees. The PCM will attempt to keep the engine speed at the Desired Idle during spark retard by slightly increasing spark advance. The engine speed may initially drop by 50 RPM then increase slightly to average 30 RPM less than the RPM observed during normal spark control.
If engine speed fails to decrease proceed to Step 4 of DTC P1350 Ignition Control System diagnosis.
5. Observe the scan tool status for the extended travel brake switch. Ensure that the extended travel brake switch status is not applied all the time. When the extended travel brake switch is applied the PCM will operates in Torque Management at high throttle angles causing timing and fuel reduction during acceleration.