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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Savana 🢒 Engine 🢒 Engine Controls - 6.5L (L65) 🢒 Fuel Pump Electrical Circuit Diagnosis

Refer to Engine Control Schematics

Cell 22: Fuel Pump Controls


Object Number: 341122 Size: FS
Engine Controls Components
Information Sensors/Switches Description
Cell 22: Fuel Controls
Cell 22: Glow Plug Controls Federal Emissions
Cell 10: Battery, Battery Junction Block, Auxiliary Battery, AUX A, AUX B, BLOWER, IGN-B, IGN-A, ABS, BATT, LIGHTING, ECM-B, HORN, A/C Fuses, Inline Fuse 30 A (Diesel Engines)
Cell 11: ECM-B, HORN, A/C Fuses
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Cell 14: G103 (6.5L)
 .

Circuit Description

When the key is turned ON, the PCM energizes the fuel pump relay which sends voltage to the lift pump. The lift pump remains ON during the glow plug cycle. If the engine is not started immediately after the glow plug cycle, the PCM shuts the fuel lift pump OFF and waits for the crank reference signal. As a backup system to the fuel pump relay, the fuel lift pump can also be turned ON by the fuel pump/oil pressure switch. When the engine oil pressure reaches 28 kPa (4 psi), the fuel pump/oil pressure switch will close and complete the circuit to run the fuel lift pump.

Diagnostic Aids

Possible long crank times or a poor performance problem will exist.

Test Description

The number(s) below refer to step number(s) on the Diagnostic Table.

  1. Checks for proper operation of the fuel pump.

    2.

  2. Checks the operation of the fuel pump by supplying 12 volts to the fuel pump control circuit.

    3.

  3. Check the battery feed circuit to the fuel pump relay.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing the DTCs, use the Scan Tool Capture Info in order to record the Freeze Frame and the failure records for reference, as the data will be lost when the Clear Info function is used.

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

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Turn the ignition OFF for 10 seconds.
  2. Turn the ignition ON.

Does the fuel pump operate during the glow plug cycle?

--

Go to Engine Cranks but Does Not Run

Go to Step 3

3

Apply a 12 volt fused jumper to the fuel pump test terminal.

Does the fuel pump operate?

--

Go to Step 4

Go to Step 8

4

  1. Disconnect the fuel pump relay.
  2. Turn the ignition ON with the engine OFF.
  3. Probe the fuel pump relay battery feed terminal at the fuel pump relay harness connector with a test light to ground.

Is the test light ON?

--

Go to Step 5

Go to Step 10

5

Connect a test light between the fuel pump relay battery feed circuit harness connector and the fuel pump relay ground at the harness connector.

Is the test light ON?

--

Go to Step 6

Go to Step 11

6
  1. Connect a test light between the fuel pump relay control circuit and ground.
  2. Turn the ignition OFF for 20 seconds.
  3. Turn the ignition ON.

Is the test light ON during glow plug cycle and then OFF?

--

Go to Step 7

Go to Step 12

7
  1. Check for a poor connection at the fuel pump relay control connector terminal.
  2. If a problem is found, repair the problem as necessary.

Was a problem found?

--

Go to Step 18

Go to Step 13

8
  1. Disconnect the fuel pump harness connector at the fuel lift pump.
  2. Apply a 12 volt fused jumper to the fuel pump test terminal.
  3. Probe the fuel pump feed circuit with a test light to ground.

Is the test light ON?

--

Go to Step 9

Go to Step 15

9

With a test light connected to B+ probe the fuel pump ground terminal (vehicle side) of the chassis harness fuel pump connector.

Is the test light ON?

--

Go to Step 14

Go to Step 16

10

Repair the open in the battery feed circuit to the fuel pump relay harness connector terminal.

Is the action complete?

--

Go to Step 18

--

11

Repair the open in the fuel pump relay ground circuit.

Is the action complete?

--

Go to Step 18

--

12
  1. Check for a poor connection at the PCM fuel pump relay control circuit.
  2. Check for an open or a short to ground in the harness between the fuel pump relay control connector terminal and the fuel pump relay control circuit.

Was a problem found?

--

Go to Step 18

Go to Step 17

13

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

Is the action complete?

--

Go to Step 18

--

14

Replace the fuel pump. Refer to Fuel Lift Pump Replacement .

Is the action complete?

--

Go to Step 18

--

15

Repair the open between the fuel pump test terminal and the fuel pump feed circuit at the fuel pump harness connector.

Is the action complete?

--

Go to Step 18

--

16

Repair the open in the fuel pump harness ground circuit.

Is the action complete?

--

Go to Step 18

--

17

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

Replace the PCM.

Is the action complete?

--

Go to Step 18

--

18
  1. Use the scan tool in order to select DTC, Clear Info.
  2. Attempt to start the engine.

Does the engine start and continue to run?

--

Go to Step 19

Go to Step 2

19
  1. Allow the engine to idle until the normal operating temperature is reached.
  2. Select DTC, Failed This Ign.

Are there any additional DTCs displayed?

--

Go to Applicable DTC Table

Go to Step 20

20

Use the scan tool in order to select Capture Info, Review Info.

Are there any additional DTCs displayed that have not been diagnosed?

--

Go to Applicable DTC Table

System OK