Electrical Test

Fuel System Electrical Test:

Circuit Description:

When the ignition switch is turned "ON" the electronic control module I ECM) will energize the fuel pump relay which completes the circuit to the in-tank fuel pump. It will remain 'ON" as long as the engine is cranking or running and the ECM is receiving a fuel control signal reference pulses). If there are no reference pulses, the ECM will de-energize the fuel pump relay within 2 seconds after key ON" or when the engine is stopped.

The fuel pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator where the system pressure is controlled. Excess fuel pressure is bypassed back to the fuel tank. When the engine is stopped, the pump can be turned "ON" by applying battery voltage to the test terminal located in the engine compartment. Improper fuel system pressure may contribute to one or all of the following symptoms:

- Cranks but won't run

- Code 44 or 45

- Cuts out, may feel like ignition problem

- Hesitation, loss of power or poor fuel economy

Fuel System Electrical Test Chart A-5:

Test Description: Number(s) refer to circled number(s) on the diagnostic chart.

1. This test checks the fuel pump relays power CKT (839) and ground CKT (450).

2. This step determines if the fuel pump circuit is being controlled by the ECM. The ECM should energize the fuel pump relay and turn the fuel pump "ON." If the engine is not cranking or running, the ECM should de-energize the relay and/or fuel pump within 2 seconds after the ignition is turned "ON."

3. This test checks for an open in CKT 465.