Schematic Reference: Engine Controls Schematics

Did you perform the Diagnostic System Check - Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

1. Disconnect the fuel heater.
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 5

1. Turn OFF the ignition.
2. Probe the fuel heater ground circuit at the fuel filter/heater element housing with a test lamp connected to battery voltage. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

Go to Step 4

Go to Step 15

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 between the fuel heater harness connector and the fuel heater. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.

Did you find an open condition?

Go to Step 21

Go to Step 12

1. Turn OFF the ignition.
2. Remove the underhood electrical center cover.
3. Inspect the HTD fuel fuse.

Is the HTD fuel fuse open?

Go to Step 6

Go to Step 8

Probe the ignition 1 voltage circuit of the fuel heater at the harness side with a test lamp connected to battery voltage. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

Go to Step 14

Go to Step 7

1. Remove the underhood electrical center cover.
2. Remove the heated fuel relay with J 43244 Relay Puller Pliers.
3. Probe the heated fuel relay battery positive voltage circuit at the underhood electrical center with a test lamp connected to battery voltage.

Does the test lamp illuminate?

Go to Step 16

Go to Step 22

1. Remove the heated fuel relay with J 43244 Relay Puller Pliers.
2. Turn ON the ignition, with the engine OFF.
3. Probe the heated fuel relay battery positive voltage circuit with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 9

Go to Step 16

1. Turn ON the ignition, with the engine OFF.
2. Probe the heated fuel relay ignition 1 voltage supply circuit with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 10

Go to Step 17

Probe the heated fuel relay ground circuit with a test lamp connected to battery voltage. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

Go to Step 11

Go to Step 18

1. Turn OFF the ignition.
2. Jumper the heated fuel relay battery positive voltage circuit and the heated fuel relay load circuit together using a fused jumper wire. Refer to Using Fused Jumper Wires in Wiring Systems.
3. Turn ON the ignition, with the engine OFF.
4. 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 20

Go to Step 13

1. Remove the fuel filter/heater element housing from the vehicle.
2. On a bench, cool the sensor part of the fuel heater with ice to below 8°C (46°F).
3. Connect the ignition 1 voltage circuit of the fuel heater to battery voltage and connect the ground circuit of the fuel heater to a good ground.
4. Observe the heating element.

Does heat occur?

Go to Step 20

Go to Step 19

Repair the open in the ignition 1 voltage circuit between the fuel filter/heater element housing and the heated fuel relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 24

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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 24

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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 24

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Repair the open or short to ground in the battery positive voltage circuit of the heated fuel relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 24

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Repair the open or short to ground in the ignition 1 voltage circuit of the heated fuel relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 24

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Repair the open in the ground circuit of the heated fuel relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 24

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Test for an intermittent and for a poor connection at the fuel heater. Refer to Testing for Intermittent Conditions and Poor Connections and Circuit Testing in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 22

Test for an intermittent and for a poor connection at the heated fuel relay. Refer to Testing for Intermittent Conditions and Poor Connections and Circuit Testing in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 23

Replace the fuel filter/heater element housing.

Did you complete the replacement?

Go to Step 24

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Replace the fuel heater.

Did you complete the replacement?

Go to Step 24

--

Replace the heated fuel relay.

Did you complete the replacement?

Go to Step 24

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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 25

Go to Step 1

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