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Engine Cooling Systems: Diagnosis Nissan Quest I

Cooling System (Mechanical) 3 illustrations ~1215 words

TROUBLE SHOOTING & TESTING

Note. ECM refers to ECCS control unit. ECM controls cooling fan operation based on inputs from coolant temperature sensor and A/C switch.

Radiator (Cooling) Fan Control Test (With A/C)

  1. Start engine and warm to operating temperature. Set temperature lever to full cold. Turn A/C switch on. Turn fan switch on. Run engine at idle with A/C on for several minutes. Ensure radiator fan operates at low speed. If radiator fan does not operate at low speed, go to RADIATOR (COOLING) FAN LOW SPEED CONTROL TEST. If radiator fan operates at low speed, go to next step.
  2. Turn A/C and fan switches off. Turn ignition off. Disconnect radiator fan relays No. 1 and No. 2. (Scheme 2)and (Scheme 3). Start engine and idle until engine temperature is greater than 221°F (105°C). Ensure radiator fan operates at high speed. Reconnect radiator fan relay No. 2. Disconnect radiator fan relay No. 3. Start engine and idle until engine is greater than 221°F (105°C). Ensure radiator fan operates at high speed. If radiator fan does not operate at high speed in either test, see RADIATOR (COOLING) FAN HIGH SPEED CONTROL TEST. If radiator fan operates at high speed, system is functioning properly.

Radiator (Cooling) Fan Control Test (Without A/C)

  1. Start engine and run at 2000 RPM until operating temperature is reached. Ensure radiator fan operates at low speed during warm-up. If radiator fan does not operate at low speed, go to RADIATOR (COOLING) FAN LOW SPEED CONTROL TEST. If radiator fan operates at low speed, go to next step.
  2. Turn A/C and fan switches off. Turn ignition off. Disconnect radiator fan relays No. 1 and 2. (Scheme 2)and (Scheme 3). Start engine and idle until engine temperature is greater than 221°F (105°C). Ensure radiator fan operates at high speed. Reconnect radiator fan relay No. 2. Disconnect radiator fan relay No. 3. Start engine and idle until engine is greater than 221°F (105°C). Ensure radiator fan operates at high speed. If radiator fan does not operate at high speed in either test, see RADIATOR (COOLING) FAN HIGH SPEED CONTROL TEST. If radiator fan operates at high speed, system is functioning properly.

Radiator (Cooling) Fan Low Speed Control Test

  1. Turn ignition off. Disconnect radiator fan relay No. 1. (Scheme 2)and (Scheme 3). Turn ignition on. Measure voltage between ground and radiator fan rela No. 1 harness connector terminals No. 2 (Blue wire) and No. 3 (Blue/Yellow wire). (Scheme 2)and (Scheme 3). Battery voltage should be present. If battery voltage is present, go to step 3). If battery voltage is not present, go to next step.
  2. Check 10-amp fuse located in fuse box under left instrument panel. Replace fuse as necessary. Check 120-amp and 65-amp fusible link located in fusible link and fuse box next to battery. Replace fusible link(s) as necessary. If fuse and fusible links are okay, repair open in appropriate harness or connectors.
  3. Turn ignition off. Disconnect radiator fan motor harness connectors. Check continuity between radiator fan motor harness connector terminal "b" (Blue/White wire) and radiator fan relay No. 1 harness connector terminal No. 5 (Blue/White wire). Check continuity between radiator fan motor harness connector terminal "c" (Black wire) and ground. (Scheme 2)and (Scheme 3). Continuity should exist in all checks. If continuity exists in all checks, go to next step. If continuity does not exist in one or more check, repair open in appropriate wire or connector.
  4. Disconnect ECM harness connector. ECM is located behind glove box. Check continuity between ECM harness connector terminal No. 9 (Blue/Orange wire) and radiator fan relay No. 1 harness connector terminal No. 1 (Blue/Orange wire). (Scheme 2), (Scheme 3) and see scheme 10. Continuity should exist. If continuity exists, go to next step. If continuity does not exist, repair open in Blue/Orange wire or connectors between ECM and relay.
  5. Check radiator fan relay No. 1. See RELAYS under COMPONENT TESTING. Replace relay as necessary. If relay is okay, check fan motors. See RADIATOR FAN MOTOR under COMPONENT TESTING. Replace motor as necessary. If fan motor is okay, check ECM and ECM harness connector for damage, corrosion or improper connection. Repair as necessary.

Scheme 2

Scheme 2
Scheme 2

Scheme 3

Scheme 3
Scheme 3

Radiator (Cooling) Fan High Speed Control Test

  1. Turn ignition off. Disconnect radiator fan relay No. 2. (Scheme 2)and (Scheme 3). Turn ignition on. Measure voltage between ground and radiator fan relay No. 2 harness connector terminals No. 2 (Blue wire) and No. 3 (Blue/Yellow wire). (Scheme 4) Battery voltage should be present. If battery voltage is present, go to step 3). If battery voltage is not present, go to next step.
  2. Check 10-amp fuse located in fuse box under left instrument panel. Replace fuse as necessary. Check 120-amp and 65-amp fusible link located in fusible link and fuse box next to battery. Replace fusible link(s) as necessary. If fuse and fusible links are okay, repair open in appropriate harness or connectors.
  3. Turn ignition off. Disconnect radiator fan relay No. 3. (Scheme 4) Check continuity between radiator fan relay No. 2 harness connector terminals No. 2 (Blue wire) and radiator fan relay No. 3 harness connector terminals No. 2 (Blue wire). Check continuity between radiator fan relay No. 2 harness connector terminals No. 3 (Blue/Yellow wire) and radiator fan relay No. 3 harness connector terminalsNo. 3 (Blue/Yellow wire). Continuity should exist in all checks. If continuity exists in all checks, go to next step. If continuity does not exist in one or more check, repair open in appropriate wire or connector.
  4. Disconnect radiator fan motor harness connector. Check continuity between radiator fan motor harness connector terminal "a" (Blue/Red wire) and radiator fan relay No. 2 harness connector terminal No. 5 (Blue/Red wire). Check continuity between radiator fan motor harness connector terminal "c" (Black wire) and ground. (Scheme 2)and (Scheme 3). Continuity should exist. If continuity exists, go to next step. If continuity does not exist, repair open in appropriate wire or connector.
  5. Check continuity between radiator fan relay No. 2 harness connector terminal No. 5 (Blue/Red wire) and radiator fan relay No. 3 harness connector terminal No. 5 (Blue/Red wire). (Scheme 4) Continuity should exist. If continuity exists, go to next step. If continuity does not exist, repair open in Blue/Red wire or connectors.
  6. Disconnect ECM harness connector. ECM is located behind glove box. Check continuity between ECM harness connector terminal No. 10 (Brown/White wire) and radiator fan relay No. 2 harness connector terminal No. 1 (Brown/White wire). (Scheme 4)and see scheme 10. Continuity should exist. If continuity exists, go to next step. If continuity does not exist, repair open in Brown/White wire or connectors between ECM and relay.
  7. Check continuity between radiator fan relay No. 2 harness connector terminal No. 1 (Brown/White wire) and radiator fan relay No. 3 harness connector terminal No. 1 (Brown/White wire). (Scheme 4) Continuity should exist. If continuity exists, go to next step. If continuity does not exist, repair open in Brown/White wire or connectors.
  8. Check radiator fan relays No. 2 and No. 3. See RELAYS under COMPONENT TESTING. Replace relay(s) as necessary. If relays are okay, check fan motor(s). See RADIATOR FAN MOTOR under COMPONENT TESTING. Replace motor(s) as necessary. If fan motors are okay, check ECM and ECM harness connector for damage, corrosion or improper connection. Repair as necessary.

Scheme 4

Scheme 4
Scheme 4

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