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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1346 (Engine Control System (Troubleshooting & Diagnosis) - 1.8L (LV6)) >> Troubleshooting >> Fuel Pump Electrical Circuit Diagnosis >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 1:  The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
  2. 2:  This step checks for the operation of the fuel pump. Fuel pump operation is difficult to hear without seat cushion removal.
  3. 5:  This step checks for the operation of the circuit opening relay. The circuit opening relay is located just above the left side kick panel and makes an audible click when turning ON and OFF.
  4. 7:  This step checks the control circuit of the fuel pump relay.
  5. 9:  The most likely location of an open circuit is between the splice and circuit opening relay terminal 2. An inoperative EFI relay would cause no MIL operation. The EFI relay is diagnosed in the No Malfunction Indicator Lamp diagnostic table.
  6. 10:  This step checks for a fault in the fuel pump or the circuit from the circuit opening relay to the fuel tank. The vehicle should start and run if the only fault was with the circuit opening relay.
Fuel Pump Electrical Circuit Diagnosis

Step Action Yes No
Schematic Reference:  Engine Controls Schematics 
1  Did you perform the Diagnostic System Check-Engine Controls? Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 
  1. Install a scan tool.
  2. Remove the bottom cushion of the rear seat in order to gain access to the fuel sender assembly access panel. Refer to Seat Cushion Replacement - Rear in Seats.
  3. Place a listening device against the fuel sender assembly access panel.
  4. Turn ON the ignition, with the engine OFF.
  5. Command the fuel pump ON and OFF with the scan tool. Refer to Scan Tool Output Controls .
  6. Listen for audible fuel pump operation.
Does the fuel pump operate as commanded?		 Go to Step 3  Go to Step 4 
3 The fuel pump electrical circuit is OK.
Do you want to inspect the fuel system for the correct operating pressure?		 Go to Fuel System Diagnosis  Go to Intermittent Conditions  in Wiring Systems
4 Is the fuel pump operating continuously when the ignition is ON and the engine is OFF? Go to Step 15  Go to Step 5 
5  Turn the fuel pump ON and OFF while listening carefully for the operation of the circuit opening relay at the left side kick panel.
Did you hear the circuit opening relay click when commanded ON and OFF by the scan tool?		 Go to Step 10  Go to Step 6 
6
  1. Turn OFF the ignition.
  2. Remove the circuit opening relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the circuit opening relay cavity 1 and cavity 5 with a test lamp connected to ground. Refer to the Relay Cavity Identification table in Diagnostic Aids.
Did the test lamp illuminate at both cavities?		 Go to Step 7  Go to Step 9 
7 
  1. Probe the circuit opening relay control circuit cavity 2 with a test lamp connected to B+.
  2. Command the fuel pump ON with the scan tool.
Does the test lamp illuminate?		 Go to Step 19  Go to Step 8 
8
  1. Check for an open in the circuit opening relay control circuit.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.
Was a wiring fault found and repaired?		 Go to Step 22  Go to Step 21 
9 
  1. Check for the cause of no ignition positive voltage to the circuit opening relay. Refer to the Test Description.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 22  -
10 
  1. Remove the fuel sender assembly access panel.
  2. Disconnect the fuel sender assembly electrical connector.
  3. Probe the fuel pump ignition positive voltage circuit, terminal 4, with a test lamp connected to ground.
  4. Command the fuel pump ON with the scan tool.
Does the test lamp illuminate?		 Go to Step 11  Go to Step 13 
11 Connect the test lamp between the fuel pump ground circuit and B+.
Does the test lamp illuminate?		 Go to Step 14  Go to Step 12 
12 Repair the open fuel pump ground circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 22  -
13 Repair the open fuel pump power circuit between the circuit opening relay and the fuel sender assembly. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 22  -
14
  1. Inspect the fuel sender assembly for an open or high resistance in the following circuits:
    • The fuel pump positive voltage circuit
    • The fuel pump ground circuit
  2. Repair or replace the fuel sender assembly as necessary. Refer to Fuel Sender Assembly Replacement (FWD) or Fuel Sender Assembly Replacement (AWD) .
Was a repair or replacement necessary?		 Go to Step 22  Go to Step 20 
15 Remove the fuel pump relay.
Is the fuel pump still operating?		 Go to Step 16  Go to Step 17 
16 Repair the short to voltage in the fuel pump supply circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 22  -
17
  1. Turn OFF the ignition.
  2. Probe the control circuit, cavity 2 of the relay socket, with a test lamp connected to B+. Refer to the Relay Cavity Identification table in Diagnostic Aids.
  3. Command the circuit opening relay ON and OFF with the scan tool.
Did the test lamp stay illuminated even when the relay was commanded OFF?		 Go to Step 18  Go to Step 19 
18
  1. Inspect for a short to ground in the control circuit of the fuel pump relay between the relay and the PCM.
  2. Repair the wiring as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and repair a wiring short?		 Go to Step 22  Go to Step 21 
19 Replace the circuit opening relay.
Did you complete the repair?		 Go to Step 22  -
20 Replace the fuel pump. Refer to Fuel Pump and Fuel Filter Assembly Replacement (with FWD) or Fuel Pump and Fuel Filter Assembly Replacement (AWD) .
Did you complete the repair?		 Go to Step 22  -
21 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the repair?		 Go to Step 22  -
22 Operate the vehicle within the conditions under which the original symptom was noted.
Does the system operate correctly now?		 System OK Go to Diagnostic Aids
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