reduced engine power light. P0641 - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > OEM Issues

OEM Issues Original Equipment Repairs and/or Problems

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  #1  
Old 08-05-2008, 03:24 AM
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mbrown2004 mbrown2004 is offline
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reduced engine power light. P0641

my service engine light has been on for about a week . then a friend drove my tb and the reduced engine light came on, wont go over about 20 mph. i parked it. it has about 10 codes on it . the one that is giving me trouble is P0641 . i had to replace the fan clutch in feb , but i never had the dealer flash the pcm ... should i have??? please help
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  #2  
Old 08-05-2008, 03:38 AM
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reduced engine power

i am kinda new at this.. but the other codes that came up were , P0452,P2135,P2138,P0526, .. i kmow that the P0526 has to do with the cooling fan speed sensor inside the fan clutch but i am wondering if i have the pcm flashed if it will fix the problems i am haveing, because like i said i replaced the fan clutch in feb. (not at the dealership) thanks
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  #3  
Old 08-05-2008, 03:48 AM
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Quote:
Originally Posted by mbrown2004 View Post
i am kinda new at this.. but the other codes that came up were , P0452,P2135,P2138,P0526, .. i kmow that the P0526 has to do with the cooling fan speed sensor inside the fan clutch but i am wondering if i have the pcm flashed if it will fix the problems i am haveing, because like i said i replaced the fan clutch in feb. (not at the dealership) thanks
P0452 Generic Evaporative Emission System Pressure Sensor/Switch Low Input
P2135 Generic Throttle/Pedal Position Sensor/Switch A / B Voltage Correlation
P2138 Generic Throttle/Pedal Position Sensor/Switch D / E Voltage Correlation
P0526 Generic Fan Speed Sensor Circuit

No Info on the first code. Sure the # is right?

Try cleaning your throttle body. If the butterfly valve in the throttle body is gummed up, as they tend to do, it will cause you all kinds of grief.
Clean it, clear the codes, and see what comes back.
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Old 08-05-2008, 04:08 AM
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the first code is right P0641 (pcm voltage out of tolerance condition on 5 volt reference) this is what i found but i have no idea what it means i am not very good with electrical issues . but i will try cleaning the throttle body in the morning ... any tips that may help me are greatly appreciated.
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Old 08-05-2008, 08:08 AM
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Quote:
Originally Posted by mbrown2004 View Post
the first code is right P0641 (pcm voltage out of tolerance condition on 5 volt reference) this is what i found but i have no idea what it means i am not very good with electrical issues . but i will try cleaning the throttle body in the morning ... any tips that may help me are greatly appreciated.
You may have the dreaded bad 2004 PCM. It is part of the emissions system so it is covered under the emissions warranty. It may only need an update but with that many codes it seems as if it is loosing communication with your TPS and other stuff
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  #6  
Old 08-05-2008, 08:17 AM
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Quote:
Originally Posted by Blazernut View Post
You may have the dreaded bad 2004 PCM. It is part of the emissions system so it is covered under the emissions warranty. It may only need an update but with that many codes it seems as if it is loosing communication with your TPS and other stuff
if that is the case my 04 tb has about 87,000 miles on it .is the pcm still covered under the emmisions warranty ? if so should the dealer replace the free of charge or will i have to pay out of pocket. i know that a pcm is not cheap but if this is the problem i dont want to start replacing other things that may not be broke.
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Old 08-05-2008, 11:29 AM
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Could be that you have a wiring issue since codes are somewhat unrelated. Check the integrity of mated connectors and the harness itself in the area of the fan clutch repair. Good idea to clean the throttle body at 87,000 if you've never had it off the TB.
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Old 08-05-2008, 11:59 AM
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on my way to pick up the trailblazer so i can start workin towards fixin the problems ... ill let ya'll know what happens.
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Old 08-05-2008, 08:29 PM
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update

ok i just cleaned the T/B put a new gas cap on and i still have reduced engine power light and SES light on. i cleared all the code and i am still getting P0641 . so i am thinking this is a pcm issue. the TPS is acting up but before i replace this part i am curios if i should take it to the dealer and have the pcm flashed and see if this fixes the problemsi am haveing ... any thoughts...
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Old 08-05-2008, 09:49 PM
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P0641-SENSOR REF VOLTAGE A CIRC/OPEN


i think its a wiring/electrical problem.
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