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Makes 🢒 Buick 🢒 1998 🢒 Park Avenue 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Fuel Pump Electrical Circuit Diagnosis

Fuel Pump Electrical Circuit Diagnosis VIN K


Object Number: 214620 Size: MF
Engine Controls Components
Cell 20: Engine Controls - PCM Fuel Control - VIN K
OBD II Symbol Description Notice

Circuit Description

When the ignition switch is first turned ON, the PCM energizes the fuel pump relay which applies power to the 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 ON 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 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 the scan tool output controls function.

Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through the wire insulation or a wire broken inside of the insulation.

Check for a poor connection or a 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

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.

  2. Checks the ignition feed circuit to the fuel pump relay.

    3.

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

    4.

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

    5.

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

    6.

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

    7.

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

    8.

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

    9.

  9. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

Fuel Pump Relay Circuit Diagnosis

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Important: If there are any other DTCs set, diagnose the DTCs first.

  1. Turn OFF the ignition switch.
  2. Disconnect the fuel pump relay.
  3. Connect a fused jumper between the B+ feed cavity and fuel pump feed cavity in the relay connector.
  4. Note the fuel pressure gauge.

Is proper fuel pressure indicated?

333-376 kPa (48-55 psi)

Go to Step 3

Go to Step 5

3

  1. Turn OFF the ignition switch.
  2. Connect a test lamp between fuel pump relay connector cavities for the fuel pump relay driver circuit and the ground circuit.
  3. Observe the test lamp while turning ON the ignition.

Did the test lamp turn ON for approximately 2 seconds?

--

Go to Step 19

Go to Step 4

4

  1. Turn OFF the ignition switch.
  2. Connect a test lamp to B+.
  3. Probe the fuel pump relay ground terminal in the relay connector.

Is the test lamp ON?

--

Go to Step 17

Go to Step 18

5

Check the fuel pump system fuse.

Is the fuse blown?

--

Go to Step 6

Go to Step 8

6

  1. Remove the fuel pump system fuse.
  2. Connect a test lamp to B+.
  3. Probe the B+ feed terminal in the relay connector.

Is the test lamp ON?

Go to Step 11

Go to Step 7

7
  1. Raise the vehicle.
  2. Disconnect the FP electrical connector.
  3. Lower the vehicle.
  4. Connect a test lamp to B+.
  5. Probe the FP feed terminal in the relay connector.

Is the test lamp ON?

Go to Step 16

Go to Step 20

8
  1. Leave the fuel pump relay disconnected.
  2. Connect a test lamp to ground.
  3. Probe the B+ feed cavity in the fuel pump relay connector.

Is the test lamp ON?

Go to Step 9

Go to Step 12

9
  1. Leave the FP relay disconnected.
  2. Connect a 15A fused jumper between the B+ feed and the FP feed cavities in the relay connector.
  3. Raise the vehicle.
  4. Disconnect the FP electrical connector.
  5. Connect a test lamp across the connector terminals.

Is the test lamp ON?

Go to Step 10

Go to Step 13

10

  1. Check for poor terminal connections between the fuel pump electrical connector and fuel pump assembly.
  2. If a problem is found, repair as necessary. Refer to Repairing Connector Terminals .

Was a problem found?

Go to Step 22

Go to Step 21

11

Locate and repair short to ground in the B+ feed to the fuel pump relay. Refer to Wiring Repairs .

Is action complete?

Go to Step 22

12

Locate and repair open in the B+ feed to the fuel pump relay. Refer to Wiring Repairs .

Is action complete?

Go to Step 22

13

Connect the test lamp between B+ feed circuit in the fuel pump connector and chassis ground.

Is the test lamp ON?

Go to Step 14

Go to Step 15

14

Locate and repair open in fuel pump ground circuit. Refer to Wiring Repairs .

Is action complete?

Go to Step 22

15

Locate and repair open in the B+ feed circuit to the fuel pump. Refer to Wiring Repairs .

Is action complete?

Go to Step 22

16

Locate and repair short to chassis/fuel pump ground. Refer to Wiring Repairs .

Is action complete?

Go to Step 22

17
  1. Check the fuel pump relay driver circuit for the following conditions:
    2. • Open or short to ground
    • Poor PCM connections
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Step 22

Go to Step 21

18

Locate and repair open in ground circuit to the fuel pump relay. Refer to Wiring Repairs .

Is action complete?

--

Go to Step 22

--

19

Replace the fuel pump relay. Refer to Fuel Pump Relay Replacement .

Is action complete?

--

Go to Step 22

--

20

Replace the fuel pump. Refer to Fuel Sender Assembly Replacement .

Is action complete?

--

Go to Step 22

--

21

Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Is action complete?

--

Go to Step 22

--

22
  1. Turn ON the ignition switch, select FP Relay output control with the scan tool.
  2. Observe the pressure gauge while turning the fuel pump ON with the scan tool.
  3. Note the fuel pressure gage.

Is proper fuel pressure indicated?

333-376 kPa (48-55 psi)

System OK

Go to Step 2

Fuel Pump Electrical Circuit Diagnosis VIN 1


Object Number: 199721 Size: LF
Engine Controls Components
Cell 20: Engine Controls - PCM Fuel and Boost Solenoid Control - VIN 1
OBD II Symbol Description Notice

Circuit Description

When the ignition switch if 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 ON 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 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 the scan tool device control function.

The PCM alters fuel pump speed by varying the duty cycle on the fuel pump speed control PWM circuit to the fuel pump control module. Under normal conditions, the fuel pump speed control PWM circuit duty cycle is set at 33%. When higher fuel volume is required due to increased engine load (MAP sensor value over 90 kPa), the PCM switches the fuel pump speed control PWM circuit duty cycle to 100%. At the higher duty cycle, the fuel pump control module increases the voltage to the in-tank fuel pump, allowing a higher volume of fuel to be delivered to the fuel rail. The PCM also compensates for low system voltage by switching the fuel pump control circuit PWM duty cycle to 100%.

Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside of the insulation.

Check for the following condition(s):

    • Poor connection at the PCM or the Fuel Pump Control Module
        Inspect the harness connectors for backed out terminals, improper mating, broken locks improperly formed or damaged terminals, and poor terminal to wire connection
    • Damaged harness.

Test Description

Numbers below refer to the Step numbers on the Diagnostic Table:

  1. Fuel pressure between the specified values is sufficient for the vehicle to start. If directed to this table from the Engine Cranks But Will Not Run table, continue diagnosis with Engine Cranks But Will Not Run.

    2.

  2. Ensures that the fuel pump speed control circuit is OK and the PCM are capable of controlling fuel pump speed.

    3.

  3. Verifies that the fuel pump high and low circuits are OK between the fuel pump control module and the fuel pump, and that the fuel pump can deliver adequate pressure to the fuel rail.

    4.

  4. Checks the feed circuit to the fuel pump control module. Using the scan tool to command the FP Speed allows only a 2 second time in the commanded state.

    5.

  5. Ensures that the fuel pump speed control circuit is not shorted to ground.

    6.

  6. Checks the battery positive voltage circuit to the fuel pump relay contacts.

    7.

  7. Checks the ground circuit for the fuel pump relay coil.

    8.

  8. Ensures that the fuel pump relay control circuit is OK and that the PCM is capable of controlling the fuel pump relay. Using the scan tool to command the fuel pump relay allows only a 2 second ON time.

    9.

  9. Checks the fuel pump relay control circuit for a short to ground.

    10.

  10. If the fuel pump is operating but incorrect pressure is observed, the fuel pump wiring is OK and the Fuel System Pressure Test should be used for diagnosis.

    11.

  11. Determines whether the problem is being caused by an open in the fuel pump high circuit or the fuel pump low circuit.

    12.

  12. Ensures that the fuel pump speed control circuit is OK and that the PCM can control the fuel pump speed control circuit. Using the scan tool to command the FP Speed allows only a 2 second time in the commanded state.

    13.

  13. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

Fuel System Electrical Test (VIN 1)

Step

Action

Values

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Is DTC P1667 set?

--

Go to DTC P1667 Fuel Pump Speed Output Circuit

Go to Step 3

3

  1. Connect a fuel pressure gauge.
  2. Turn ON the ignition switch.
  3. Select Fuel Pump output control with the scan tool.
  4. Observe the pressure gauge while commanding the fuel pump ON with the scan tool.

Is fuel pressure indicated at the specified value?

333-376 kPa (48-55 psi)

Go to Step 4

Go to Step 5

4

Important:: If the engine cranks but will not run, continue with Engine Cranks but Does Not Run

  1. Start the engine.
  2. Select FP Speed output control with the scan tool.
  3. Observe the pressure gauge while using the scan tool to switch FP Speed between normal and high.

Does the fuel pressure increase slightly when high fuel pump speed is selected?

--

System OK

Go to Step 31

5

  1. Turn OFF the ignition switch.
  2. Disconnect the fuel pump control module.
  3. Connect a fused jumper between the fuel pump high circuit (fuel pump control module harness connector terminal 6) and B+.
  4. Connect a second jumper between the fuel pump low circuit (fuel pump control module harness connector terminal 5) and chassis ground.
  5. Observe the fuel pressure gauge.

Is fuel pressure indicated at the specified value?

333-376 kPa (48-55 psi)

Go to Step 6

Go to Step 26

6

  1. Disconnect the jumpers from the fuel pump control module connector
  2. Connect a test lamp between the fuel pump control module feed circuit (fuel pump control module harness connector terminal 8) and chassis ground.
  3. Turn ON the ignition switch.
  4. Command the fuel pump ON using the scan tool output controls function.
  5. Observe the test lamp.

Is the test lamp ON with the fuel pump commanded ON?

--

Go to Step 7

Go to Step 13

7

Probe the fuel pump control module ground circuit (fuel pump control module connector terminal 4) with a test lamp to B+.

Is the test lamp ON?

--

Go to Step 8

Go to Step 25

8

  1. Turn OFF the ignition switch.
  2. Disconnect the PCM.
  3. Probe the fuel pump speed control circuit at the PCM connector with a test lamp to B+.

Is the test lamp ON?

--

Go to Step 9

Go to Step 10

9

Locate and repair short to ground in the fuel pump speed control circuit. Refer to Wiring Repairs in Wiring Systems.

Is action complete?

--

Go to Step 39

--

10
  1. Turn OFF the ignition switch.
  2. Reconnect the PCM.
  3. Turn ON the ignition switch.
  4. Install a DMM.
  5. Command the Fuel Pump ON using the scan tool output controls function.

Does the voltage measure greater than the specified value while the fuel pump relay is commanded ON?

8V

Go to Step 11

Go to Step 38

11
  1. Turn OFF the ignition switch.
  2. Reconnect the fuel pump control module electrical connector.
  3. Turn ON the ignition switch.
  4. Using a test lamp, backprobe between the fuel pump high circuit (fuel pump control module connector terminal 6) and the fuel pump low circuit (fuel pump control module connector terminal 5).
  5. Command the Fuel Pump ON using the scan tool output controls function.

Is the test lamp ON while the fuel pump is commanded ON?

--

Go to Step 12

Go to Step 34

12
  1. Check for poor connections at the fuel pump control module.
  2. If a problem is found, repair as necessary. Refer to one or more of the following procedures in Wiring Systems:

Was a problem found?

--

Go to Step 39

Go to Diagnostic Aids

13

  1. Turn OFF the ignition switch.
  2. Disconnect the fuel pump relay.
  3. Turn ON the ignition switch.
  4. Probe the fuel pump relay battery positive voltage circuit with a test lamp to chassis ground.

Is the test lamp ON?

--

Go to Step 14

Go to Step 19

14

Connect the test lamp between the fuel pump relay battery positive voltage circuit relay ground circuit.

Is the test lamp ON?

--

Go to Step 15

Go to Step 20

15

  1. Connect the test lamp between the fuel pump relay control circuit and the fuel pump relay ground circuit.
  2. Command the Fuel Pump ON using the scan tool output controls function.

Is the test lamp ON with the fuel pump relay commanded ON?

--

Go to Step 16

Go to Step 21

16
  1. Connect a jumper between the fuel pump relay battery positive voltage circuit pump control module feed circuit.
  2. Probe the fuel pump control module feed circuit at the fuel pump control module (fuel pump control module harness connector terminal 8) with a test lamp to ground

Is the test lamp ON?

--

Go to Step 17

Go to Step 24

17
  1. Check for poor terminal connections at the fuel pump relay.
  2. If a problem is found, repair as necessary. Refer to one or more of the following procedures in Wiring Systems:

Is action complete?

--

Go to Step 39

Go to Step 18

18

Replace the fuel pump relay. Refer to Fuel Pump Relay Replacement .

Is action complete?

--

Go to Step 39

--

19

Locate and repair open in fuel pump relay battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Is action complete?

--

Go to Step 39

--

20

Locate and repair open in fuel pump relay ground circuit. Refer to Wiring Repairs in Wiring Systems.

Is action complete?

--

Go to Step 39

--

21

  1. Turn OFF the ignition switch.
  2. Disconnect the PCM.
  3. Probe the fuel pump relay control circuit at the PCM connector with a test lamp to B+.

Is the test lamp ON?

--

Go to Step 22

Go to Step 23

22

Locate and repair short to ground in the fuel pump relay control circuit. Refer to Wiring Repairs in Wiring Systems.

Was the problem found?

--

Go to Step 39

--

23
  1. Check for the following conditions:
    2. • The fuel pump relay control circuit open between the fuel pump relay and the PCM.
    • Poor fuel pump relay control circuit terminal connection at the PCM.
  2. If a problem is found, repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Was a problem found?

--

Go to Step 39

Go to Step 38

24

Locate and repair open in the fuel pump control module feed circuit. Refer to Wiring Repairs in Wiring Systems.

Is action complete?

--

Go to Step 39

--

25

Locate and repair open in the fuel pump control module ground circuit. Refer to Wiring Repairs in Wiring Systems.

Is action complete?

--

Go to Step 39

--

26

Remove the fuel filler cap and listen for the fuel pump running.

Is the fuel pump running?

--

Go to Fuel System Pressure Test (VIN K) or Fuel System Pressure Test (VIN 1)

Go to Step 27

27
  1. Leave the fuel pump high circuit jumpered to B+ and the fuel pump low circuit jumpered to ground at the fuel pump control module connector.
  2. Remove the modular fuel sender access cover. Refer to Fuel Sender Assembly Replacement .
  3. Disconnect the modular fuel sender electrical connector at the fuel tank.
  4. Connect a test lamp between the fuel pump high circuit and the fuel pump low circuit at the modular fuel sender harness connector.

Is the test lamp ON?

--

Go to Step 36

Go to Step 28

28

Probe the fuel pump high circuit at the modular fuel sender harness connector with a test lamp to chassis ground.

Is the test lamp ON?

--

Go to Step 30

Go to Step 29

29

Locate and repair open or short to ground in the fuel pump high circuit. Refer to Wiring Repairs in Wiring Systems.

--

Go to Step 39

--

30

Locate and repair open or short to voltage in the fuel pump low circuit. Refer to Wiring Repairs in Wiring Systems.

Is action complete?

--

Go to Step 39

--

31

  1. Using a test lamp, backprobe between the fuel pump speed control circuit (fuel pump control module terminal 7) and the fuel pump control module feed circuit (fuel pump control module terminal 8).
  2. Engine idling, select FP Speed output control with the scan tool.
  3. Observe the test lamp while switching FP Speed between normal and high.

Is the test lamp ON with Normal selected and OFF with High selected?

--

Go to Step 32

Go to Step 33

32
  1. Using a DMM.
  2. Engine idling, select FP Speed output control with the scan tool.
  3. Observe the fuel pump speed control circuit voltage on the DMM while switching FP Speed between normal and high:
    4. • Normal speed voltage is the first value shown.
    • High speed voltage is the second value shown.

Does the voltage measure near the specified values?

3.5V

11V

Go to Step 36

Go to Step 34

33
  1. Check for the following conditions:
    2. • The fuel pump speed control circuit shorted to voltage or open between the fuel pump control module and the PCM. Refer to Wiring Repairs in Wiring Systems.
    • Poor fuel pump speed control circuit terminal connection at the PCM. Refer to Repairing Connector Terminals in Wiring Systems.
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 39

Go to Step 38

34
  1. Check for poor terminal connections at the fuel pump control module.
  2. If a problem is found, repair as necessary. Refer to one or more of the following procedures in Wiring Systems:

Was a problem found?

--

Go to Step 39

Go to Step 35

35

Replace the fuel pump control module. Refer to Fuel Pump Control Module Replacement .

Is action complete?

--

Go to Step 39

--

36
  1. Check for poor terminal connections at the fuel pump.
  2. If a problem is found, repair as necessary. Refer to one or more of the following procedures in Wiring Systems:

Was a problem found?

--

Go to Step 39

Go to Step 37

37

Replace the fuel pump. Refer to Fuel Sender Assembly Replacement .

Is action complete?

--

Go to Step 39

--

38

Important: : The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Is action complete?

--

Go to Step 39

--

39
  1. Turn ON the ignition switch.
  2. Select Fuel Pump output control with the scan tool.
  3. Observe the fuel pressure gauge while commanding the fuel pump ON with the scan tool.

Is fuel pressure indicated at the specified value?

333-376 kPa (48-55 psi)

Go to Step 40

Go to Step 5

40
  1. Engine idling, select FP Speed output control with the scan tool.
  2. Observe the pressure gauge while using the scan tool to switch FP Speed between normal and high.

Does the fuel pressure increase slightly when high fuel pump speed is selected?

--

System OK

Go to Step 31