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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1049 (Engine Controls Diagnosis - 6.6L (LLY) (DTC P2229 To DTC P2636)) >> Diagnosis >> DTC P2636 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. 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. 3:  This step determines if the condition is on the coil side, or the switch side of the fuel pump relay.
  2. 11:  This step verifies the fuel transfer pump operation. If the test lamp flashes, then the fuel transfer pump and circuits are OK.
DTC P2636

Step Action Values 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 Is DTC P0461, P0462, P0463, P2067, or P2068 also set? - Go to Diagnostic Trouble Code (DTC) List in Instrument Panel, Gages, and Console Go to Step 3 
3 
IMPORTANT: The fuel level must be between 25-50 percent in order to perform this diagnostic procedure. If the fuel level is not within this range, misdiagnosis will occur.
  1. Turn ON the ignition, with the engine OFF.
  2. Command the fuel pump relay ON and OFF with a scan tool.
Does the fuel pump relay click?		 - Go to Step 9  Go to Step 4 
4
  1. Remove the fuel pump relay from the underhood electrical center.
  2. Probe the ground circuit of the fuel pump relay with a test lamp that is connected to battery voltage. Refer to Probing Electrical Connectors and Circuit Testing in Wiring Systems.
Does the test lamp illuminate?		 - Go to Step 5  Go to Step 25 
5
  1. Probe the fuel pump relay control circuit with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems.
  2. Command the fuel pump relay ON and OFF with a scan tool.
Does the test lamp turn ON and OFF?		 - Go to Step 22  Go to Step 6 
6 Does the test lamp remain illuminated? - Go to Step 7  Go to Step 8 
7 Test the fuel pump relay control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 31  Go to Step 24 
8 Test the fuel pump relay control circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 31  Go to Step 24 
9 Command the fuel transfer pump ON with a scan tool.
Does the fuel transfer pump operate?		 - Go to Step 17  Go to Step 10 
10
  1. Remove the fuel pump relay from the underhood electrical center.
  2. Turn ON the ignition, with the engine OFF.
  3. Probe the battery voltage circuit of the fuel pump relay with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 11  Go to Step 12 
11  Connect a fused jumper wire between the fuel pump relay battery voltage circuit and the fuel pump supply voltage circuit.
Does the fuel pump operate?		 - Go to Step 22  Go to Step 15 
12 Is the battery positive voltage fuse open? - Go to Step 13  Go to Step 27 
13 Test the battery voltage circuit of the fuel pump relay for a short to ground.
Did you find and correct the condition?		 - Go to Step 31  Go to Step 14 
14 Test the fuel pump supply voltage circuit for a short to ground.
Did you find and correct the condition?		 - Go to Step 31  Go to Step 23 
15 Test the fuel transfer pump supply voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 31  Go to Step 16 
16 Probe the ground circuit of the fuel transfer pump with a test lamp that is connected to battery voltage.
Does the test lamp illuminate?		 - Go to Step 23  Go to Step 26 
17 Observe the fuel level sensor rear tank voltage parameter with a scan tool.
Is the voltage less than the specified value?		 2.2 V Go to Step 19  Go to Step 18 
18 Add the specified amount of fuel to the rear fuel tank.
Did you complete the action?		 19 L (5 Gal) Go to Step 19  -
19
  1. Connect a fused jumper wire between the fuel pump relay battery voltage circuit and the fuel pump voltage supply circuit.
  2. Observe the rear Fuel Level sensor voltage parameter with a scan tool.
Does the rear fuel level sensor voltage increase as the fuel pump is operating?		 - Go to Step 20  Go to Step 21 
20
  1. Disconnect the outlet hose from the fuel transfer pump.
  2. Connect a section of rubber hose with a clamp to the outlet port of the transfer pump.
  3. Insert the other end of the rubber hose into a container to measure more than 4 Liters (1.06 gallons).
  4. Operate the transfer pump with a scan tool for a total of 120 seconds.
  5. Measure the fuel in the container.
Does the fuel volume measure more than the specified value?		 2.6 L (0.70 gal) Go to Intermittent Conditions Go to Step 21 
21 Inspect for the following conditions:
  • A restriction in the fuel lines between the front and rear fuel tanks
  • The rear fuel sender for a restriction

Did you find and correct the condition?		 - Go to Step 31  Go to Step 29 
22 Inspect for poor connections at the harness connector of the fuel pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 31  Go to Step 28 
23 Inspect for poor connections at the harness connector of the fuel transfer pump. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 31  Go to Step 29 
24 Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 31  Go to Step 30 
25 Repair the open ground circuit of the fuel pump relay. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 31  -
26 Repair the open ground circuit of the fuel transfer pump. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 31  -
27 Repair the open battery voltage circuit of the fuel pump relay. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 31  -
28 Replace the fuel pump relay.
Did you complete the replacement?		 - Go to Step 31  -
29 Replace the fuel transfer pump. Refer to Fuel Pump Replacement (Cab/Chassis) .
Did you complete the replacement?		 - Go to Step 31  -
30 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 31  -
31
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Diagnostic Aids Go to Step 32 
32 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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