For 1990-2009 cars
Engine Controls Components
Fuel Control
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

When the ignition switch is first turned ON, the PCM energizes the fuel pump relay which applies power to the in-tank fuel pump. The fuel pump relay will remain ON as long as the engine is running or cranking and the PCM is receiving reference pulses. If no reference pulses are present, the PCM de-energizes the fuel pump relay within 2 seconds after the ignition is turned or the engine is stopped.

The fuel pump delivers fuel to the fuel rail and injectors, then to the fuel pressure regulator. The fuel pressure regulator, a vacuum sensitive device, controls fuel pressure by allowing excess fuel to be returned to the fuel tank. With the engine stopped, the fuel pump can be turned ON by using a fused jumper to apply battery positive voltage to the fuel pump test lead in the engine compartment.

### Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following items:

• | Poor connection or damaged harness.

• | Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

### Test Description

The number(s) below refer to the Step number(s) on the Diagnostic Table:

1. Verifies that the fuel pump feed circuit is OK between the fuel pump relay and the fuel pump, and that the fuel pump can deliver adequate pressure to the fuel rail.

2. Checks the fuel pump relay battery positive voltage feed and relay coil ground circuits.

3. Ensures that the fuel pump relay driver circuit and the PCM are capable of controlling the fuel pump relay.

4. Checks the fuel pump driver circuit for a short to ground.

5. Checks the fuel pump driver circuit for an open.

6. If the fuel pump is operating but incorrect pressure is noted, the fuel pump wiring is OK. The Fuel System Diagnosis should be used for diagnosis.

7. Checks the fuel pump feed circuit between the fuel pump relay and the fuel pump. Also checks the fuel pump ground circuit.

8. Determines whether the problem is being caused by an open in the fuel pump feed circuit or the fuel pump ground circuit.

#### Fuel System Electrical Test

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain OBD System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn OFF the ignition switch.
2. Connect a fuel pressure gage to the fitting on the fuel rail.
3. Connect a fused jumper between the fuel pump test terminal in the engine compartment and battery positive voltage.
4. Note the fuel pressure gage.

Is proper fuel pressure indicated?

284-325 kPa (41-47 psi)

Go to Step 3

Go to Step 10

3 |

1. Disconnect the jumper from the fuel pump test terminal.
2. Remove the fuel pump relay from the relay connector.
3. Connect a J 35616-200 between fuel pump relay connector cavities for the battery positive Voltage feed circuit and the relay ground circuit.
4. Observe the test light.

Is the test light ON?

--

Go to Step 4

Go to Step 9

4 |

1. Turn OFF the ignition switch.
2. Connect a test light between fuel pump relay connector cavities for the ignition feed circuit (from the PCM) and the relay ground circuit.
3. Observe the test light while turning on the ignition.

Did the test light turn ON for approximately 2 seconds?

--

Go to Step 8

Go to Step 5

5 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Probe the fuel pump relay circuit at the PCM connector with a test light to battery positive voltage.

Is the test light ON?

--

Go to Step 15

Go to Step 6

6 |

1. Check for continuity in the fuel pump relay circuit between the PCM and the fuel pump relay.
2. If the fuel pump relay circuit is open, repair it as necessary.

Was the fuel pump relay circuit open?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 7

7 |

1. Check the fuel pump relay circuit for a poor terminal connection at the PCM.
2. If a problem is found, replace terminal as necessary. Refer to Connector Repairs in Wiring Systems.

Was a problem found?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 20

8 |

1. Check for a poor terminal connection at the fuel pump relay.
2. If a problem is found, replace terminal(s) as necessary. Refer to Connector Repairs in Wiring Systems.

Was a problem found?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 18

9 | Probe the battery positive voltage feed circuit at the fuel pump relay connector with a test light to engine ground. Is the test light ON? | -- | Go to Step 17 | Go to Step 16
10 | Remove the fuel filler cap and listen for the fuel pump running. Is the fuel pump running? | -- | Go to Fuel System Diagnosis | Go to Step 11
11 |

1. Raise the vehicle (leave the fuel pump feed circuit jumped to battery positive voltage).
2. Disconnect the modular fuel sender electrical connector at the fuel tank.
3. Connect a test light between the fuel pump feed circuit and the fuel pump ground circuit at the modular fuel sender harness connector.

Is the test light ON?

--

Go to Step 19

Go to Step 12

12 | Probe the fuel pump feed circuit at the modular fuel sender harness connector with a test light to chassis ground. Is the test light ON? | -- | Go to Step 13 | Go to Step 14
13 | Locate and repair open in the fuel pump ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
14 | Locate and repair open in the fuel pump feed circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
15 | Locate and repair short to ground in the fuel pump relay PCM feed circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
16 | Locate and repair open in ignition feed to the fuel pump relay. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
17 | Locate and repair open in ground circuit to the fuel pump relay. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
18 | Replace the fuel pump relay. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
19 | Replace the fuel pump. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
20 | Important: : Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming Replace the PCM. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --