My Envoy has a trouble code P0495. Technician's preliminary analysis is a failed cooling fan clutch. Car is not overheating. Does the clutch typically fail in the locked position and manifest itself with a loud racing sound? Is there a relay that engages the fan clutch? If so, how do I perform the necessary fault analysis to isolate the specific problem?
Thank you!
Test
sorry for the 'test' post. I realize this question is old, but many people will search for it, so I am answering...
your problem is definitely the fan clutch. replace it asap or it will tear up the front bearing in your water pump, followed by your belt and plastic shroud housing. It's expensive but necessary. It is the big grey-metal looking thing with heat fins that the plastic radiator fan is bolted to. It can not be fixed [afaik] and must be replaced. It can go bad even after only 3-5 years. If your notor sounds like a jet taking off all the time, this is the bad boy. replace asap!
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Schematic Reference: Engine Cooling
Schematics
Connector End View Reference: Cooling System
Connector End Views
1
Did you perform the Engine Cooling Diagnostic System Check?
Go to Step 2
Go to Diagnostic
System Check - Engine Cooling
2
Does the scan tool indicate the DTC Failed this ignition cycle?
Go to Step 5
Go to Step 3
3
Important: DTC P1482, for 4.2L (LL8), and P0480, for
5.3L (LM4), will set when the cooling fan relay is disconnected.
Does the cooling fan clutch engage?
Go to Step 4
Go to Step 5
4
Important: Continuously excessive fan noise is due
to the PCM commanding the cooling fan clutch to 100% engaged or a mechanical
failure. If the fan noise decreases during this step, then this DTC is due to an
electrical malfunction. Replacing the cooling fan clutch will not correct the
condition.
Does the cooling fan clutch disengage?
Go to Step 5
Go to Step 11
5
Is the Fan Speed parameter less than 1600 RPM?
Go to Diagnostic Aids
Go to Step 6
6
Does the cooling fan rotate freely?
Go to Step 7
Go to Step 13
7
Does the test lamp illuminate?
Go to Step 8
Go to Step 11
8
Disconnect the cooling fan relay.
Does the test lamp remain illuminated?
Go to Step 9
Go to Step 10
9
Repair the cooling fan clutch supply voltage circuit of the cooling fan
clutch for a short to voltage. Refer to Wiring
Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 14
--
10
Inspect for poor connections at the cooling fan relay. Refer to Testing for
Intermittent Conditions and Poor Connections and to Connector
Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 14
Go to Step 12
11
Inspect for poor connections at the cooling fan clutch. Refer to Testing for
Intermittent Conditions and Poor Connections and to Connector
Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 14
Go to Step 13
12
Replace the cooling fan relay.
Did you complete the replacement?
Go to Step 14
--
13
Replace the cooling fan clutch. Refer to Fan Clutch
Replacement .
Did you complete the replacement?
Go to Step 14
--
14
Does the DTC reset?
Go to Step 2
System OK
I have a 2003 trailblazer with a code P0495. Making a loud
fan noise, but not over heating
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