Test 3

For EGR function testing, see appropriate ENGINE PERFORMANCE section.

ECM operates a Vacuum Switching Valve (VSV) to control vacuum to EGR valve. This solenoid is normally closed. ECM provides a ground to solenoid and VSV opens, allowing vacuum to EGR valve.

Engine control system operates within 2 block learn cells, a closed throttle cell and an open throttle cell. Open throttle cell is affected by EGR operation. When EGR system is operating correctly, block learn in both cells should be approximately the same. If EGR system is inoperative, block learn value at open throttle would increase, but block learn value at closed throttle would not change. This change or difference in block learn values is used to monitor EGR operation.

If EGR system works properly, check for restricted EGR passages or defective MAP sensor. These items could cause high block learn values in open throttle, but not in closed throttle.

Fig 1: Chart C-7A - Schematic

Courtesy of ISUZU MOTOR CO.

Fig 2: Chart C-7A - Flow Chart

Courtesy of ISUZU MOTOR CO.