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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1001 (Engine Controls - 6.6L (LLY) (Troubleshooting & Diagnosis)) >> Troubleshooting >> Fuel Heater Inoperative >> 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 number below refers to the step number on the diagnostic table.

  1. 5:  This steps checks for a thermostatic switch that completes the circuit.
Fuel Heater Inoperative

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
1 Does the Water In Fuel lamp operate properly? - Go to Step 2  Go to Water-in-Fuel Lamp Always On in Instrument Panel, Gages, and Console
2
  1. Disconnect the fuel heater harness connector from the top of the fuel filter/heater element housing.
  2. Turn ON the ignition with the engine OFF.
  3. Probe the fuel heater ignition 1 voltage circuit with a test lamp connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
Does the test lamp illuminate?		 - Go to Step 3  Go to Step 6 
3 Probe the fuel heater ground circuit at the fuel filter/heater element housing with a test lamp connected to B+. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
Does the test lamp illuminate?		 - Go to Step 4  Go to Step 8 
4
  1. Remove the fuel filter from the fuel filter/heater element housing.
  2. Test the ignition 1 voltage circuit and the ground circuit for an open in the fuel filter/heater element housing. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.
Did either circuit test open?		 - Go to Step 9  Go to Step 5 
5 
  1. Remove the fuel filter/heater element housing from the vehicle.
  2. Connect the ignition 1 voltage circuit of the fuel heater to battery voltage source and connect the ground circuit of the fuel heater to the ground of the voltage source.
  3. Cool the sensor part of the fuel heater with ice.
  4. Observe the heating element.
Does the thermostatic switch turn ON when the temperature is within the specified range?		 -8.4 to +15.4°C (+16.9 to +59.8°F) Go to Step 11  Go to Step 10 
6 Repair the open in the ignition 1 voltage circuit between the fuel filter/heater element housing and the fuse. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 11  -
7 Repair the short to ground on the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 11  -
8 Repair the open in the ground circuit between the fuel filter/heater element housing and chassis ground. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 11  -
9 Replace the fuel filter/heater element housing. Refer to Fuel Filter/Heater Element Housing Replacement .
Did you complete the replacement?		 - Go to Step 11  -
10 Replace the fuel heater. Refer to Fuel Filter/Heater Element Housing Replacement .
Did you complete the replacement?		 - Go to Step 11  -
11 Operate the vehicle under which the problem was noted.
Does the system operate properly?		 - System OK Go to Step 1 
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