Fuel Pump Electrical Circuit Diagnosis

Diagnostic Chart (Part 1 Of 3):

Diagnostic Chart (Part 2 Of 3):

Diagnostic Chart (Part 3 Of 3):

Schematic:

CIRCUIT DESCRIPTION
When the ignition switch is turned ON, the Powertrain Control Module (PCM) turns ON the in-tank fuel pump. It will remain ON as long as the PCM is receiving ignition reference pulses from the electronic Ignition Control Module (ICM). If there are no reference pulses, the PCM will shut OFF the fuel pump about 2-3 seconds after the ignition is turned ON, about 10 seconds after the reference pulses stop.

The fuel pump delivers fuel to the fuel rail and fuel injectors, then to the fuel pressure regulator, where the system pressure is controlled to 283-324 kPa (41-47 psi) with no manifold vacuum or 214-303 kPa (31-44 psi) at idle. Excess fuel is then returned to the fuel tank.

Improper fuel system pressure will result in one or all of the following symptoms:
^ Cranks but will not run
^ DTC P0171
^ DTC P0172
^ DTC P1171
^ DTC P0300
^ Cuts out, may feel like an ignition problem
^ Poor fuel economy, loss of power
^ Hesitation

DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection, rubbed through wire insulation or a broken wire inside the insulation. check for a poor connection or damaged harness. Inspect the PCM harness and connectors for the following items:
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminals
^ Poor terminal to wire connections
^ Damaged harnesses

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. Command both the ON and OFF states. Repeat the commands as necessary.
3. This step determines if the condition is located on the coil side or the switch side of the circuit.
4. This step verifies that the PCM is providing voltage to the fuel pump relay.
5. This step tests for an open in the ground circuit to the fuel pump relay.
6. This step determines if a voltage is constantly being applied to the fuel pump relay.
15. Use the same amp fuse the circuit is protected with
20. This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.
28. The replacement PCM must be programmed and the Crankshaft Position System Variation Learn procedure must be performed.