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Home >> Chevrolet >> 2006 >> Cobalt LTZ >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 5 (Engine Controls - 2.0L - Troubleshooting & Diagnosis) >> Fuel Pump Electrical Circuit Diagnosis >> Circuit Description

Circuit Description

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The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within two seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within two seconds if ignition reference pulses cease to be detected and the ignition remains ON.

Fuel Pump Electrical Circuit Diagnosis

Step Action Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Powertrain Control Module (PCM) Connector End Views  or  Engine Controls Connector End Views 
1 Did you perform the Diagnostic System Check - Vehicle? Go to Step 2  Go to DIAGNOSTIC SYSTEM CHECK - VEHICLE
2
  1. Turn ON the ignition, with the engine OFF.
  2. Command the fuel pump relay ON and OFF with a scan tool.
  3. Repeat the commands as necessary.
Does the fuel pump turn ON and OFF?		 Go to Intermittent Conditions  Go to Step 3 
3 Command the fuel pump relay ON and OFF with a scan tool.
Do you hear the fuel pump relay click when you command the fuel pump relay ON and OFF?		 Go to Step 9  Go to Step 4 
4
  1. Turn OFF the ignition.
  2. Remove the fuel pump relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the control circuit of the fuel pump relay with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors .
  5. Command the fuel pump relay ON and OFF with a scan tool.
Does the test lamp turn ON and OFF?		 Go to Step 5  Go to Step 6 
5
  1. Connect a test lamp between the control circuit of the fuel pump relay and the ground circuit of the fuel pump relay.
  2. Command the fuel pump relay ON and OFF with a scan tool.
Does the test lamp turn ON and OFF?		 Go to Step 21  Go to Step 24 
6 Does the test lamp remain illuminated with each command? Go to Step 7  Go to Step 8 
7 Test the control circuit of the fuel pump relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 29  Go to Step 28 
8 Test the control circuit of the fuel pump relay for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 29  Go to Step 22 
9 Turn ON the ignition, with the engine OFF.
Does the fuel pump operate continuously?		 Go to Step 10  Go to Step 11 
10
  1. Turn OFF the ignition.
  2. Remove the fuel pump relay.
  3. Turn ON the ignition, with the engine OFF.
Does the fuel pump operate continuously?		 Go to Step 23  Go to Step 27 
11 Inspect the fuel pump fuse.
Is the fuel pump fuse open?		 Go to Step 12  Go to Step 15 
12
  1. Disconnect the fuel pump module harness from the body pass-through connector.
  2. Test the supply voltage circuit of the fuel pump for a short to ground between the fuel pump relay and the body pass-through connector. Refer to Circuit Testing and Wiring Repairs .
  3. Replace the fuel pump fuse if necessary.
Did you find and correct the condition?		 Go to Step 29  Go to Step 13 
13
  1. Lower the fuel tank. Refer to Fuel Tank Replacement .
  2. Inspect the fuel pump module harness on top of the fuel tank for the following conditions:
  3. Replace the fuel pump fuse if necessary.
Did you find and correct the condition?		 Go to Step 29  Go to Step 14 
14
  1. Connect all disconnected electrical components.
  2. Install a new fuel pump fuse.
  3. Command the fuel pump relay ON with a scan tool.
  4. Inspect the fuel pump fuse.
Is the fuel pump fuse open?		 Go to Step 26  Go to Intermittent Conditions 
15
  1. Turn OFF the ignition.
  2. Remove the fuel pump relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the battery voltage circuit of the fuel pump relay, switch side, with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors .
Does the test lamp illuminate?		 Go to Step 16  Go to Step 25 
16 Connect a 15-amp fused jumper wire between the battery voltage circuit of the fuel pump relay and the supply voltage circuit of the fuel pump.
Does the fuel pump operate?		 Go to Step 21  Go to Step 17 
17
  1. Disconnect the fuel pump module harness from the body pass-through connector.
  2. Test the supply voltage circuit of the fuel pump for an open or high resistance between the fuel pump relay and the body pass-through connector. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 29  Go to Step 18 
18
IMPORTANT: Inspect the ground circuit for proper torque, corrosion on the terminals, or damage to the wiring harness.
Test the ground circuit of the fuel pump for an open or high resistance between the body pass-through connector and ground. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?		 Go to Step 29  Go to Step 19 
19 Test for an intermittent and for a poor connection at the fuel pump module harness to the body pass-through connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 Go to Step 29  Go to Step 20 
20
  1. Lower the fuel tank. Refer to Fuel Tank Replacement .
  2. Inspect the fuel pump module harness on top of the fuel tank for the following conditions:
Did you find and correct the condition?		 Go to Step 29  Go to Step 26 
21 Test for an intermittent and for a poor connection at the fuel pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 Go to Step 29  Go to Step 27 
22 Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 Go to Step 29  Go to Step 28 
23 Repair the short to voltage in the supply voltage circuit of the fuel pump. Refer to Wiring Repairs .
Did you complete the repair?		 Go to Step 29  -
24 Repair the open or high resistance in the ground circuit of the fuel pump relay. Refer to Wiring Repairs .
Did you complete the repair?		 Go to Step 29  -
25 Repair the open in the battery voltage circuit of the fuel pump relay. Refer to Wiring Repairs .
Did you complete the repair?		 Go to Step 29  -
26
IMPORTANT: Inspect for poor connections at the fuel pump, within the fuel tank, before replacing the fuel pump.
  1. Replace the fuel pump module. Refer to Fuel Pump Module Replacement .
  2. Replace the fuel pump fuse if necessary.
Did you complete the replacement?		 Go to Step 29  -
27 Replace the fuel pump relay.
Did you complete the replacement?		 Go to Step 29  -
28 Replace the PCM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 Go to Step 29  -
29 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 2 
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