Fuel Pump Electrical Circuit Diagnosis

Schematic:

CIRCUIT DESCRIPTION
When the ignition is turned ON, the Powertrain Control Module (PCM) turns ON the in-tank fuel pump. The pump 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 filter/regulator, then to the fuel rail and fuel injectors. The system pressure is controlled to 380-410 kPa (55-60 psi). Excess fuel is returned to the fuel tank through the fuel return hose located on the fuel filter.

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 wire broken 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

Diagnostic Chart (Part 1 Of 3):

Diagnostic Chart (Part 2 Of 3):

Diagnostic Chart (Part 3 Of 3):

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the Freeze Frame and Failure Records data on the scan tool, if applicable. This creates an electronic copy of the data captured when this DTC sets. The scan tool stores this data for later reference.
2. If the no start condition was due to an open fuse, locate and repair any shorts that may have caused the fuse to open before the replacement.
3. This step determines if the PCM can control the fuel pump. The PCM should energize the fuel pump relay and turn ON the fuel pump when commanded by the scan tool. If the engine is not cranking or running, the PCM should de-energize the relay and turn OFF the fuel pump after 2-3 seconds.
4. Connecting a fused jumper wire between the fuel pump feed terminal and the fuel pump relay ignition feed terminal verifies that the following circuits are all OK:
^ Fuel pump relay ignition feed circuit
^ Fuel pump feed circuit
^ Fuel pump
^ Fuel ground
7. This step checks for an open in the fuel pump ground circuit.
16. Reprogram the replacement PCM and perform the Crankshaft Position System Variation Learn Procedure. Refer to the latest Techline information for PCM programming.
20. This test will determine if a short to ground on the fuel pump feed circuit or the fuel injector feed circuit caused the fuse to open.