Chart A-5 - Fuel Pump Relay Circuit

When ignition switch is turned to ON position, ECM activates fuel pump relay to run fuel pump. ECM activates relay as long as it receives ignition reference signals or starter crank signal. If no reference signals are received by ECM within 2 seconds after ignition is turned on, ECM cuts off power to relay.

1. If fuse is blown, check for short to ground on circuit No. 120. To prevent misdiagnosis, ensure fuel pump is disconnected and ignition is off before testing.
2. Determines if ECM and fuel pump relay circuit are operating correctly. ECM should activate fuel pump relay. Since engine is not cranking or running, ECM will deactivate relay within 2 seconds after ignition is turned on.

Fig 1: Chart A-5 - Schematic

Courtesy of ISUZU MOTOR CO.

Fig 2: Chart A-5 - Diagnostic Flowchart

Courtesy of ISUZU MOTOR CO.