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Engine Cooling Fan: Other Pontiac Aztek I

Cooling Fan ~2372 words

ELECTRIC COOLING FAN CONTROL

The engine cooling fan system is controlled by the Body control module (BCM) and the Powertrain Control Module (PCM). The BCM performs the calculations as to how long, when and what speed the cooling fans should turn on. The BCM then sends a class 2 message to the PCM to engage the cooling fan relays. If there is a malfunction with the BCM, the PCM will control the engine cooling fans independently. The engine cooling system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the PCM to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood accessory wiring junction block. The ground path is provided at G100.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cooling fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 2 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 3 relay and the cooling fan 2 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 2 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage from the cooling fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed. The BCM and PCM command Low Speed Fans on under the following conditions

  1. The engine coolant temperature exceeds approximately 223°F (106°C).
  2. The A/C refrigerant pressure exceeds 190 psi (1310 kPa).
  3. The vehicle is shut off when the engine coolant temperature is greater than 284°F (140°C) and system voltage is more than 12 volts. The fans will stay ON for approximately 3 minutes.

The BCM and PCM command High Speed Fans on under the following conditions

  1. The engine coolant temperature reaches 230°F (110°C).
  2. The A/C refrigerant pressure exceeds 240 psi (1655 kPa).
  3. When certain DTCs set.

PRELIMINARY INFORMATION

This article contains only the text required to test electric cooling fans. Other diagnostic information may be referenced while performing electric cooling fan diagnosis. See appropriate ENGINE PERFORMANCE articles for complete information on engine control systems.

To help save diagnostic time, always check for blown fuses or fusible links before proceeding with any testing. If fuses are blown, locate and repair short circuit before replacing fuses. See appropriate FUSES & CIRCUIT BREAKERS article in ELECTRICAL. Ensure all related relay and wire harness connections are clean and tight. Repair as necessary. See WIRING DIAGRAMS for component, terminal and wire color identification.

Intermittents

Intermittent faulty electrical connections or wiring may be the cause of intermittent conditions. Check for loose, bent or corroded terminals and terminal tension. Check for cut, bare or pinched wiring. Simulate the condition that is potentially causing the intermittent connection, either by wiggling the connections or the wiring, test driving or performing other operations while observing scan tool, DVOM or other testing equipment.

COOLING FAN ALWAYS ON

  1. Did you perform the DIAGNOSTIC SYSTEM CHECK - ENGINE COOLING? If so, go to next step. If not, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE COOLING»(ref-167983-S41088261232004102700000) under SELF - DIAGNOSTIC.
  2. Turn ON the ignition, with the engine OFF. Are one or both cooling fans ON? If so, go to next step. If not, see «INTERMITTENTS»(ref-167983-S39517138632004102700000) in SYMPTOMS - ENGINE COOLING under TROUBLE SHOOTING.
  3. Are both cooling fans running continuously? If so, go to next step. If not, go to step 6 .
  4. Are both cooling fans running continuously in high speed? If so, go to next step. If not, go to step 7
  5. Test the low reference circuit of the A/C refrigerant pressure sensor for an open. Did you find and correct the condition? If so, go to step 18 . If not, go to step 14 .
  6. Remove the cooling fan 3 or S/P relay. Did the right cooling fan turn OFF? If so, go to step 10 . If not, go to step 8 .
  7. Remove the cooling fan 1 relay. Did the cooling fans turn OFF? If so, go to step 12 . If not, go to step 9 .
  8. Remove the cooling fan 2 relay. Did the right cooling fan turn OFF? If so, go to step 13 . If not, go to step 11 .
  9. Repair the short to voltage in the left cooling fan motor supply voltage circuit. After repairs are complete, go to step 18 .
  10. Repair the short to voltage in the left cooling fan low reference circuit. After repairs are complete, go to step 18 .
  11. Repair the short to voltage in the right cooling fan motor supply voltage circuit. After repairs are complete, go to step 18 .
  12. Inspect for poor connections at the cooling fan 1 relay. Did you find and correct the condition? If so, go to step 18 . If not, go to step 15 .
  13. Inspect for poor connections at the cooling fan 2 relay. Did you find and correct the condition? If so, go to step 18 . If not, go to step 16 .
  14. Inspect for poor connections at the A/C refrigerant pressure sensor. Did you find and correct the condition? If so, go to step 18 . If not, go to step 17
  15. Replace the cooling fan 1 relay. After replacement is complete, go to step 18 .
  16. Replace the cooling fan 2 relay. After replacement is complete, go to step 18 .
  17. Replace the A/C refrigerant pressure sensor. See A/C PRESSURE SENSOR in appropriate MANUAL HVAC article in HVAC. After replacement, go to next step.
  18. Operate the system in order to verify the repair. Did you correct the condition? If so, then system is okay. If not, go to step 2 .

COOLING FAN INOPERATIVE

  1. Did you perform the DIAGNOSTIC SYSTEM CHECK - ENGINE COOLING? If so, go to next step. If not, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE COOLING»(ref-167983-S41088261232004102700000) under SELF-DIAGNOSTIC.
  2. Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the FANS LOW SPEED ON and OFF. Do the low speed engine cooling fans turn ON and OFF with each command? If so, go to next step. If not, go to step 4 . NOTE: A 3 second delay occurs before the Powertrain Control Module (PCM)/Engine Control Module (ECM) changes the cooling fan speed.
  3. With a scan tool, command the FANS HIGH SPEED ON and OFF. Do the high speed engine cooling fans turn ON and OFF with each command? If so, see «INTERMITTENTS»(ref-167983-S39517138632004102700000) in SYMPTOMS - ENGINE COOLING under TROUBLE SHOOTING. If not, go to step 11 . NOTE: DO NOT remove the 20 Amp fused jumper wire connected during this step. Use a second 20 A fused jumper wire while performing the following steps.
  4. Disconnect the cooling fan 1 relay. Connect the first 20-Amp fused jumper between the battery positive voltage circuit of the cooling fan 1 relay and the cooling fan motor supply voltage circuit of the cooling fan 1 relay. Do both cooling fans operate in low speed? If so, go to step 13 . If not, go to next step.
  5. Disconnect the cooling fan s/p relay. Connect the second 20-Amp fused jumper between the left cooling fan motor low reference circuit of the cooling fan 2 relay and the right cooling fan motor supply voltage circuit of the cooling fan 2 relay. Do both cooling fans operate in low speed? If so, go to step 14 . If not, go to next step.
  6. Reconnect the second 20-Amp fused jumper between the battery positive voltage circuit of the cooling fan 2 relay and the cooling fan motor supply voltage circuit of the cooling fan 2 relay. Does the right cooling fan operate in high speed? If so, go to step 9 . If not, go to next step.
  7. Install the cooling fan 2 relay. Disconnect the right cooling fan electrical connector. Reconnect the second 20-Amp fused jumper wire from the cooling fan motor supply voltage circuit of the right cooling fan electrical connector to the cooling fan motor ground circuit of the right cooling fan electrical connector. Does the left cooling fan operate in high speed? If so, go to step 16 . If not, go to next step.
  8. Reconnect the second 20-Amp fused jumper wire from the cooling fan motor supply voltage circuit of the right cooling fan electrical connector to a good ground. Does the left cooling fan operate in high speed? If so, go to step 20 . If not, go to step 21 .
  9. Install the cooling fan 2 relay. Disconnect the left cooling fan electrical connector. Reconnect the second 20-Amp fused jumper wire from cooling fan motor supply voltage circuit of the left cooling fan electrical connector to the cooling fan low reference circuit of the left cooling fan electrical connector. Does the right cooling fan operate in high speed? If so, go to step 17 . If not, go to next step.
  10. Reconnect the second 20-Amp fused jumper wire from battery positive voltage to the left cooling fan low reference circuit of the of the left cooling fan electrical connector. Does the right cooling fan operate in high speed? If so, go to step 18 . If not, go to step 22 .
  11. Does the right cooling fan operate in high speed? If so, go to next step. If not, go to step 15 .
  12. Disconnect the cooling fan 2 relay. Connect a 20-Amp fused jumper between the left cooling fan low reference circuit of the cooling fan 2 relay and the ground circuit of the cooling fan 2 relay. Does the left cooling fan operate properly in high speed? If so, go to step 14 . If not, go to step 19 .
  13. Inspect for poor connections at the cooling fan 1 relay. Did you find and correct the condition? If so, go to step 28 . If not, go to step 23 .
  14. Inspect for poor connections at the cooling fan 2 relay. Did you find and correct the condition? If so, go to step 28 . If not, go to step 24 .
  15. Inspect for poor connections at the cooling fan 3 or S/P relay. Did you find and correct the condition? If so, go to step 28 . If not, go to step 25 .
  16. Inspect for poor connections at the harness connector of the right cooling fan. Did you find and correct the condition? If so, go to step 28 . If not, go to next step.
  17. Inspect for poor connections at the harness connector of the left cooling fan. Did you find and correct the condition? If so, go to step 28 . If not, go to next step.
  18. Repair the left cooling fan motor supply voltage circuit. After repairs are complete, go to step 28 .
  19. Repair the left cooling fan motor ground circuit. After repairs are complete, go to step 28 .
  20. Repair the right cooling fan motor ground circuit. After repairs are complete, go to step 28 .
  21. Repair the right cooling fan motor supply voltage circuit. Did you complete the repair? After repairs are complete, go to step 28 .
  22. Repair the left cooling fan low reference circuit. After repairs are complete, go to step 28 .
  23. Replace the cooling fan 1 relay. After replacement is complete, go to step 28 .
  24. Replace the cooling fan 2 relay. After replacement is complete, go to step 28 .
  25. Replace the cooling fan 3 or S/P relay. After replacement is complete, go to step 28 .
  26. Replace the right cooling fan. See «COOLING FAN MOTOR»(ref-167983-S29228436552004102700000) under REMOVAL & INSTALLATION. After replacement is complete, go to step 28 .
  27. Replace the left cooling fan. See «COOLING FAN MOTOR»(ref-167983-S29228436552004102700000) under REMOVAL & INSTALLATION. After replacement is complete, go to next step.
  28. Operate the system in order to verify the repair. Did you correct the condition? If so, then system is okay. If system is not okay, go to step 3 .

ENGINE COOLANT TEMPERATURE INDICATOR ALWAYS ON

  1. Did you perform the DIAGNOSTIC SYSTEM CHECK - ENGINE COOLING? If so, go to next step. If not, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE COOLING»(ref-167983-S41088261232004102700000) under SELF-DIAGNOSTIC.
  2. Start the engine. Does the engine coolant temperature indicator illuminate? If so, go to next step. If not, see «INTERMITTENTS»(ref-167983-S39517138632004102700000) in SYMPTOMS - ENGINE COOLING under TROUBLE SHOOTING.
  3. With the scan tool, observe the ENGINE COOLANT TEMPERATURE PARAMETER in the Powertrain Control Module (PCM) or Engine Control Module (ECM) data list. Does the scan tool indicate that the coolant temperature is within the temperature range shown on the temperature gage? If so, go to «ENGINE OVERHEATING»(ref-167983-S18247958072004102700000) . If not, go to next step.
  4. Replace the IPC. See appropriate GAUGES & INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs are complete, go to next step.
  5. Operate the system in order to verify the repair. Did you correct the condition? If so, then system is okay. If system is not okay, go to 2 .

ENGINE OVERHEATING

Check for possible causes of engine overheating. Inspect and fill the cooling system as necessary.

RELAYS (WITHIN AN ELECTRICAL CENTER)

Note. Required Tools: Relay Puller Pliers (J-43244)

Note. Always note the orientation of the relay. Ensure that the electrical center is secure, as not to put added stress on the wires or terminals.

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