GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The fuel manager/filter assembly mounted to the engine consists of the fuel heater and the secondary fuel filter.

The fuel passes through the fuel heater assembly to the secondary fuel filter. The fuel heater assembly contains ceramic heater and a thermostatic switch that opens or closes to turn the heater OFF or ON. The thermostatic switch completes the ground circuit for the fuel heater when fuel temperature is below 15.4°C (59.8°F).

The fuel then passes through the fuel filter and to the fuel injection pump.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematic Icons

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Disconnect the fuel heater connector.
  2. Remove the fuel heater from the filter housing. Refer to Fuel Filter Assembly Replacement .
  3. With the fuel heater at room temperature, connect the ignition 1 voltage circuit of the fuel heater harness connector to battery voltage and connect the ground circuit of the fuel heater harness connector to a good ground.
  4. Observe the heater element.

Does heat occur?

--

Go to Step 4

Go to Step 3

3

  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 (16.9-59.8°F)

Go to Step 5

Go to Step 4

4

Replace the fuel heater. Refer to Fuel Filter Assembly Replacement .

Did you complete the replacement?

--

Go to Step 5

--

5

  1. Start the engine.
  2. Operate the vehicle within the Condition for which the problem was noted.

Does the fuel heater operate properly?

--

Go to Step 6

Go to Step 1

6

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