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.

2: This step checks for a fuel heater that is stuck ON.
3: This steps checks for a thermostatic switch that completes the circuit.

Fuel Heater Always On

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics
1	Does the Water In Fuel lamp operating properly?	-	Go to Step 2	Go to Water-in-Fuel Lamp Always On in Instrument Panel, Gages, and Console
2	Disconnect the fuel heater connector and remove the fuel heater from the filter housing. Refer to Fuel Filter/Heater Element Housing Replacement . With the fuel heater at room temperature, connect the ignition 1 voltage circuit of the fuel heater to B+ and connect ground circuit of the fuel heater to ground. Observe the heater element. Does heat occur?	-	Go to Step 4	Go to Step 3
3	Remove the fuel filter/heater element housing from the vehicle. 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. Cool the sensor part of the fuel heater with ice. 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 5	Go to Step 4
4	Replace the fuel heater. Refer to Fuel Filter/Heater Element Housing Replacement . Did you complete the replacement?	-	Go to Step 5	-
5	Operate the vehicle under which the problem was noted. Does the system operate properly?	-	System OK	Go to Step 1