Schematic Reference: Engine Cooling Schematics

Turn ON the ignition, with the engine OFF. Does the heater water auxiliary pump operate?

Go to Step 2

Go to Heater Water Auxiliary Pump Inoperative

Make sure the engine temperature is below 95°C (203°F).

Are the auxiliary engine coolant fans and/or the electric cooling fan operating with the engine temperature below 95°C (203°F)?

Go to Cooling Fan Always On - Auxiliary

Go to Step 3

1. Connect a 5 Amp fused jumper between the fan control relay K26 diagnostic enable circuit and a known ground.
2. Grounding of the fan control relay K26 diagnostic enable circuit will simulate the closing of the primary coolant fan temperature switch stage 1 contacts, this will energize the fan control relay K26.

Does the auxiliary engine coolant fan #1 and auxiliary engine coolant fan #2 operate at low speed?

Go to Step 4

Go to Cooling Fan Inoperative - Auxiliary

Observe the electric cooling fan.

Is the electric cooling fan operating at low speed?

Go to Step 5

Go to Cooling Fan Inoperative

1. Turn OFF the ignition.
2. Leave all previously connected jumpers connected.

Does the water auxiliary pump operate?

Go to Step 6

Go to Auxiliary Water Pump Inoperative

1. Turn ON the ignition, with the engine OFF.
2. Leave all previously connected jumpers connected.
3. Connect a 5 Amp fused jumper between the fan control relay K28 and fan control relay K52 diagnostic enable circuit and a known good ground.
4. Grounding of the fan control relay K28 and fan control relay K52 diagnostic enable circuit will simulate the closing of the secondary cooling fan temperature switch, this will energize the fan control relay K28 and fan control relay K52.

Does the auxiliary engine coolant fan #1 operate at high speed?

Go to Step 7

Go to Cooling Fan Inoperative - Auxiliary

Observe the auxiliary engine coolant fan  #2.

Does the auxiliary engine coolant fan #2 operate at high speed?

Go to Step 8

Go to Cooling Fan Inoperative - Auxiliary

1. Leave all previously connected jumpers connected.
2. Connected a 5 Amp fused jumper between the fan control relay K67 diagnostic enable circuit and a known good ground.
3. Grounding of the fan control relay K67 diagnostic enable circuit will simulate the closing of the primary cooling fan temperature switch stage 2 contacts. This will energize the fan control relay K67.

Does the electric cooling fan operate at high speed?

Go to Step 9

Go to Cooling Fan Inoperative

1. Remove all previously connected jumpers.
2. Start the engine and allow it to run.
3. Turn the A/C compressor clutch coil ON.

Does the auxiliary engine coolant fan #1 and auxiliary engine coolant fan #2 operate at low speed when the compressor clutch coil is turned ON?

Go to Step 10

Go to Cooling Fan Inoperative - Auxiliary

1. Install the scan tool.
2. Monitor the engine coolant temperature using the scan tool.
3. Remove any previously connected jumpers.
4. Turn the A/C compressor clutch coil OFF.
5. Allow the engine to run until the primary cooling fan temperature switch reaches 100°C (212°F). The stage 1 contacts should close and energize the fan control relay K26.

Does the auxiliary engine coolant fan #1 and auxiliary engine coolant fan #2 operate at low speed?

Go to Step 11

Go to Step 12

Continue to allow the engine to run until the secondary cooling fan temperature switch reaches 105°C (221°F). The secondary cooling fan temperature switch should close and energize the fan control relay K28 and fan control relay K52.

Does the auxiliary engine coolant fan #1 and auxiliary engine coolant fan #2 operate at high speed?

Go to Step 15

Go to Step 16

Test the control circuit of the fan control relay K26 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 13

Test the ground circuit of the primary cooling fan temperature switch for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 14

Replace the primary cooling fan temperature switch. Refer to Engine Cooling Fan Control Switch Replacement .

Did you complete the repair?

Go to Step 21

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Continue to allow the engine to run until the primary cooling fan temperature switch reaches 110°C (230°F). The stage 2 contacts should close and energize the fan control relay K67.

Does the electric cooling fan operate at high speed?

Go to Step 20

Go to Step 18

Test the control circuit of the fan control relay K28 and fan control relay K52 for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 17

Replace the secondary cooling fan temperature switch. Refer to Engine Cooling Fan Control Switch Replacement .

Did you complete the repair?

Go to Step 21

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Test the fan control relay K67 control circuit of the relay coil for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 21

Go to Step 19

Replace the primary cooling fan temperature switch. Refer to Engine Cooling Fan Control Switch Replacement .

Did you complete the repair?

Go to Step 21

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1. Install the A/C manifold gauge set to monitor A/C refrigerant pressure.
2. Turn the A/C compressor clutch coil ON.
3. Continue to operate the engine until the A/C refrigerant pressure switches reaches 1896 kpa (275 psi).

Does the auxiliary engine coolant fan #1 and auxiliary engine coolant fan #2 operate at high speed?

Go to Step 21

Go to Cooling Fan Inoperative - Auxiliary

Do the engine cooling fans and the auxiliary water pumps operate properly?

System OK

Go to Step 1