Mechanics

CHEVY REPLACED THE LOW COOLANT LEVEL SENSOR, LI

2000 Chevrolet Impala

Engine Cooling problem
2000 Chevy Impala 6 cyl Two Wheel Drive Automatic 80000 miles

Found that fans do not come on, except when AC is on. Does this sensor cover this problem as well? It only overheats if the AC is not on.
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Phoneguy70
July 6, 2010.




Yes it does along with relays for high and low fan. Relays are usually in the underhood relay center.
3.4L & 3.8L " W" BODY (IMPALA & MONTE CARLO) Description Engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. Relays are arranged in a series/parallel configuration that allows Powertrain Control Module (PCM) to operate both fans together at low or high speeds. Cooling fans and fan relays receive battery voltage from engine wiring harness junction block. During low speed operation, PCM supplies ground path for low speed fan relay through low speed cooling fan relay control circuit. This energizes cooling fan 1 relay coil, closes relay contacts, and supplies battery voltage from FAN CONT 1 fuse through cooling fan motor supply voltage circuit to right cooling fan. Ground path for right cooling fan is through cooling fan 2 relay and left cooling fan. Result is a series circuit with both fans running at low speed. During high speed operation, PCM supplies ground path for cooling fan 1 relay through low speed cooling fan relay control circuit. After a 3-second delay, PCM supplies ground path for cooling fan 2 relay and cooling fan 3 relay through high speed cooling fan relay control circuit. This energizes cooling fan 2 relay coil, closes relay contacts, and provides a ground path for right cooling fan. At the same time, cooling fan 3 relay coil is energized closing relay contacts and provides battery voltage from FAN CONT 2 fuse on cooling fan motor supply voltage circuit to left cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. Result is a parallel circuit with both fans running at high speed. PCM commands low speed fans on under the following conditions: Engine coolant temperature exceeds approximately 223 F (106 C). When A/C is requested and ambient temperature is greater than 122 F (50 C). A/C refrigerant pressure exceeds 190 psi. After vehicle is shut off, if engine coolant temperature at key-off is greater than 284 F (140 C) and system voltage is more than 12 volts. Fans will stay on for approximately 3 minutes. PCM commands High Speed Fans on under the following conditions: Engine coolant temperature reaches 230 F (110 C). A/C refrigerant pressure exceeds 240 psi. When certain DTCs set. Diagnostic System Check 1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article. 2. Turn ignition on, engine off. Try to establish scan tool communication with Instrument Cluster (IC) and Powertrain Control Module (PCM). If communication with IC and PCM is established, go to next step. If communication with IC and PCM is not established, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article. 3. Select display DTC function for PCM. Record all displayed DTCs and status of displayed DTCs. If DTCs are displayed, go to next step. If no DTCs are displayed, see COOLING FAN INOPERATIVE or COOLING FAN ALWAYS ON. 4. If scan tool does not display DTCs beginning with " U", see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If scan tool displays DTCs beginning with " U", see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article. Cooling Fan Inoperative 1. If diagnostic system check has been performed, go to next step. If diagnostic system check has not been performed, see DIAGNOSTIC SYSTEM CHECK. 2. Install scan tool. Turn ignition on, engine off. Using scan tool, command fans low speed on and off. If low speed engine cooling fans turn on and off with each command, go to next step. If low speed engine cooling fans do not turn on and off with each command, go to step 4. 3. Using scan tool, command fans high speed on and off. If high speed engine cooling fans turn on and off with each command, problem is intermittent. If high speed engine cooling fans do not turn on and off with each command, go to step 11. 4. Disconnect cooling fan 1 relay. Connect fused jumper (20-amp) between battery voltage circuit (Orange wire) of cooling fan 1 relay and cooling fan motor supply voltage circuit (Gray wire) of cooling fan 1 relay. If both cooling fans operate in low speed, go to step 13. If both cooling fans do not operate in low speed, go to next step. 5. Disconnect cooling fan 2 relay. Connect second fused jumper (20-amp) between right cooling fan low reference circuit (White wire) of cooling fan 2 relay and left cooling fan motor supply voltage circuit (Light Blue wire) of cooling fan 2 relay. If both cooling fans operate in low speed, go to step 14. If both cooling fans do not operate in low speed, go to next step. 6. Connect second fused jumper (20-amp) between battery voltage circuit (Orange wire) of cooling fan 2 relay and cooling fan motor supply voltage circuit (Light Blue wire) of cooling fan 2 relay. If left cooling fan operates in high speed, go to step 9. If left cooling fan does not operate in high speed, go to next step. 7. Install cooling fan 2 relay. Disconnect left cooling fan electrical connector. Connect second fused jumper (20-amp) between terminals of left cooling fan electrical connector. If right
NOTE: Before PCM changes speed of cooling fan, a 3-second delay occurs. NOTE: Do not remove fused jumper (20-amp) connected during this step. Use a second fused jumper (20-amp) while performing the following steps.
Cooling fan operates in high speed, go to step 16. If right cooling fan does not operate in high speed, go to next step. 8. Connect second fused jumper (20-amp) between cooling fan motor supply voltage circuit (Light Blue wire) of left cooling fan electrical connector and ground. If right cooling fan operates in high speed, go to step 20. If right cooling fan does not operate in high speed, go to step 21. 9. Install cooling fan 2 relay. Disconnect right cooling fan electrical connector. Connect second fused jumper (20-amp) between terminals of right cooling fan electrical connector. If left cooling fan operates in high speed, go to step 17. If left cooling fan does not operate in high speed, go to next step. 10. Connect second fused jumper (20-amp) between battery voltage and right cooling fan low reference circuit (White wire) of right cooling fan electrical connector. If left cooling fan operates in high speed, go to step 18. If left cooling fan does not operate in high speed, go to step 22. 11. If left cooling fan operates properly in high speed, go to next step. If left cooling fan does not operate properly in high speed, go to step 15. 12. Disconnect cooling fan 2 relay. Connect second fused jumper (20-amp) between right cooling fan low reference circuit (White wire) of cooling fan 2 relay and ground circuit (Black wire) of cooling fan 2 relay. If right cooling fan operates properly in high speed, go to step 14. If right cooling fan does not operate properly in high speed, go to step 19. 13. Check cooling fan 1 relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 28. If problem was not found, go to step 23. 14. Check cooling fan 2 relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 28. If problem was not found, go to step 24. 15. Check cooling fan 3 relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 28. If problem was not found, go to step 25. 16. Check left cooling fan connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 28. If problem was not found, go to step 26. 17. Check right cooling fan connector for poor connections. If problem was found, repair as necessary. After repairs, go to step 28. If problem was not found, go to step 27. 18. Repair right cooling fan motor supply voltage circuit (Gray wire). After repairs, go to step 28. 19. Repair right cooling fan ground circuit (Black wire). After repairs, go to step 28. 20. Repair left cooling fan ground circuit (Black wire). After repairs, go to step 28. 21. Repair left cooling fan motor supply voltage circuit (Light Blue wire). After repairs, go to step 28. 22. Repair right cooling fan low reference circuit (White wire). After repairs, go to step 28. 23. Replace cooling fan 1 relay. After repairs, go to step 28. 24. Replace cooling fan 2 relay. After repairs, go to step 28. 25. Replace cooling fan 3 relay. After repairs, go to step 28. 26. Replace left cooling fan. After repairs, go to step 28. 27. Replace right cooling fan. After repairs, go to next step. 28. Operate system to verify repair.

Merlin2021
Jul 6, 2010.


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