For 1990-2009 cars
Engine Controls Components
Cell 20: Fuel Controls
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Fuel Pump relay coil is supplied power via the Engine Controls Power Relay (switched B+). The Engine Control Module (ECM) controls the relay by grounding the control circuit via an internal solid state device called a driver. When the ECM detects reference pulses from the Crankshaft Position sensor, the ECM will enable the fuel pump. On the switch side of the relay, one of the relay contacts is connected directly to battery positive voltage (B+). The relay controls the power to the Fuel Pump fuse and the fuel pump.

### Diagnostic Aids

Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.

The following conditions may have caused the fuel pump fuse to open:

• | The fuse was damaged

• | There is an intermittent short in the fuel pump power feed circuit.

• | The fuel pump has an intermittent internal problem.

#### Fuel Pump Circuit Diagnosis

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Check the fuel pump fuse. Is the fuse open? | -- | Go to Step 11 | Go to Step 3
3 |

1. Disconnect the fuel pump relay.
2. Probe the battery feed circuit in the fuel pump relay harness connector with test light J 34142-B connected to ground.

Does the test light illuminate?

--

Go to Step 4

Go to Step 13

4 |

1. Turn on the ignition.
2. Probe the Switched B+ circuit in the fuel pump relay harness connector with test light J 34142-B connected to ground.

Does the test light illuminate?

--

Go to Step 5

Go to Step 14

5 |

1. Probe the control circuit in the fuel pump relay harness connector with test light J 34142-B connected to B+.
2. Crank the engine while observing the test light.

Does the test light illuminate?

--

Go to Step 7

Go to Step 6

6 |

1. Turn off the ignition.
2. Disconnect the ECM.
3. Check the harness for continuity of the relay control circuit with the DVM J 39200 .

Is continuity indicated?

--

Go to Step 24

Go to Step 15

7 | Use a fused jumper wire in order to jumper the battery feed circuit to the fuel pump circuit in the fuel pump relay harness connector. The fuel pump should run. Does the fuel pump run? | -- | Go to Step 22 | Go to Step 8
8 |

1. Leave the fused jumper wire connected.
2. Check for power to the fuel pump fuse with test light J 34142-B connected to ground.

Does the test light illuminate?

--

Go to Step 9

Go to Step 16

9 |

1. Leave the fused jumper wire connected.
2. Re-install the fuel pump fuse if previously removed.
3. Check for power to the fuel pump at the fuel pump harness connector with the test light J 34142-B connected to ground.

Does the test light illuminate?

--

Go to Step 10

Go to Step 17

10 | Probe the ground circuit in the fuel pump harness connector with test light J 34142-B connected to B+. Does the test light illuminate? | -- | Go to Step 18 | Go to Step 20
11 |

1. Turn off the ignition.
2. Remove the fuel pump fuse.
3. Disconnect the fuel pump harness connector at the fuel pump.
4. Probe the power feed circuit in the fuel pump harness connector with test light J 34142-B connected to B+.

Does the test light illuminate?

--

Go to Step 21

Go to Step 12

12 |

1. Reconnect the fuel pump.
2. Install a new fuel pump fuse.
3. Attempt to start the engine.
4. Recheck the fuel pump fuse.

Is the fuse open?

--

Go to Step 19

No Trouble Found. Refer to Diagnostic Aids

13 | Repair the open battery feed circuit. Is the action complete? | -- | Go to Step 26 | --
14 | Repair the open/high resistance Switched B+ circuit to the Fuel Pump relay. Is the action complete? | -- | Go to Step 26 | --
15 | Repair the open/high resistance relay control circuit. Is the action complete? | -- | Go to Step 26 | --
16 | Repair the open/high resistance fuel pump fuse feed circuit. Is the action complete? | -- | Go to Step 26 | --
17 | Repair the open/high resistance fuel pump feed circuit. Is the action complete? | -- | Go to Step 26 | --
18 | Check for a poor connection or poor harness damage at the fuel pump. Was a problem found and corrected? | -- | Go to Step 26 | Go to Step 19
19 | Replace the fuel pump. Refer to Service Category Engine Fuel. Is the action complete? | -- | Go to Step 26 | --
20 | Repair the open/high resistance fuel pump ground circuit. Is the action complete? | -- | Go to Step 26 | --
21 | Repair the fuel pump feed circuit shorted to ground. Is the action complete? | -- | Go to Step 26 | --
22 | Check for any poor connections at the relay. Was a problem found and corrected? | -- | Go to Step 26 | Go to Step 23
23 | Replace the relay. Is the action complete? | -- | Go to Step 26 | --
24 | Check for a poor connections or poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

Was a problem found and corrected?

--

Go to Step 26

Go to Step 25

25 | Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 26

--

26 |

1. Select DTC, Clear Info with the scan tool.
2. Attempt to start the engine.

Does the engine start and continue to run?

--

Go to Step 27

Go to Step 2

27 |

1. Allow the engine to idle until the normal operating temperature is reached.
2. Check for any DTCs. with the scan tool.

Are any DTCs displayed?

--

Go to the applicable DTC table

Go to Step 28

28 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | The System is OK