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Old 01-01-2020, 09:07 PM   #1
rws1012
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Low power on 2001 6.0

I have a 2001 2500 HD with a 6.0 that loses power on hills and really loses power pulling a load. It has 148000 miles on it. Have changed plugs, wires, and cleaned mass air sensor after I got a code for it. Didn't seem to help. Drives down the road pretty good. Will cat converters stop up and cause this problem or is it something else? I did blow a large hole in the flowmaster muffler coming home the other day. All help appreciated
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Old 01-01-2020, 10:31 PM   #2
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Re: Low power on 2001 6.0

I seen a baffle in a flow master get closed off one time and it also caused the truck to lose power.
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Old 01-02-2020, 09:36 AM   #3
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Re: Low power on 2001 6.0

I am assuming you have checked for any codes in your system? Yes a clogged cat/exhaust can cause issues. Normally, I would think a clogged cat would throw a code though. I have honestly never had a cat issue that I knew of before close to 300K + miles on them.
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Old 01-02-2020, 11:42 PM   #4
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Re: Low power on 2001 6.0

Thanks for the reply's. I will put my HF code checker on it tomorrow and will post results. Spent today spending gift card and playing with new toys. LOL!!!
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Old 01-03-2020, 07:56 PM   #5
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Re: Low power on 2001 6.0

Put code checker on my truck. Had 1 code. P0404 which reader said it was exhaust gas recirculation control , circuit range / performance.
What to do now. Do these trucks have same type EG valve as the old trucks? I don't have vacuum lines on my truck. All help appreciated.
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Old 01-04-2020, 03:33 AM   #6
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Re: Low power on 2001 6.0

Yes, I believe 2001 was the last year of the EGR valve for the LS motor. You can unplug the connector to the EGR valve and see if it makes a difference. If no difference is noted, then your EGR valve is likely bad. Easy replacement. Two 10mm bolts and itís located right on top, passenger side, front. Some people just clean it, but I rather just replace. Cleaning seems to be only a temp fix.
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Old 01-14-2020, 11:37 PM   #7
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Re: Low power on 2001 6.0

I put a patch on my muffler nd disconnected the egr valve. Drove the truck to town and it did pretty good. Did throw a service engine code. if it does better does that mean the egr is bad? All help appreciated.
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Old 01-15-2020, 03:26 PM   #8
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Re: Low power on 2001 6.0

Unpluging the EGR motor wont prove if it's bad or not. The egr would be closed at idle, then open up at cruise. If the truck idles ok it's probably not stuck open. It could still be bad, or not opening up enough for the O2's to pick up on egr flow. I've had bad 02's give horrible throttle response, almost like a blocked cat. Need more than a code reader to look at some data to see what's going on. Could have a knock sensor acting goofy under load and pulling a bunch of timing or a coil/coils going bad.
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Old 01-15-2020, 09:08 PM   #9
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Re: Low power on 2001 6.0

Thanks for the reply biketopia. Been wondering if O2 sensors could be bad. It has 4 on it. It idles just fine. Was going to try and find a mechanic that has a computer like they use to have in the good old days. LOL!! Have never changed O2 sensors or coils on this truck. Bought it new. One mechanic told me the O2 sensors should be changed at 30,000 miles. Don't know about that. Will get the muffler changed first. Will check into the EGR thing second. Thank you
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Old 01-16-2020, 01:45 PM   #10
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Re: Low power on 2001 6.0

There's no need to change the o2's at 30k, or any mileage for that matter unless they are bad. When the truck loses power does the check engine light flash?
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Old 01-17-2020, 12:43 AM   #11
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Re: Low power on 2001 6.0

Yes the service engine soon light comes on. Usually when I start up a hill and try to stay at 65mph. Thanks for the reply.
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Old 01-17-2020, 07:48 AM   #12
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Re: Low power on 2001 6.0

But does it flash? If it's flashing that indicates it's currently misfiring. If you could have your code reader while you're driving and see if maybe you get a different code from the EGR code when it acts up?
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Old 01-18-2020, 01:00 AM   #13
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Re: Low power on 2001 6.0

No it is not flashing . It comes on and stays on until I turn the truck off. Thanks for the help. I will take it out again tomorrow and drive it around.
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Old 01-28-2020, 07:09 PM   #14
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Re: Low power on 2001 6.0

I have driven my truck a couple of times and it seems to drive ok. No codes. Will hook a trailer up and see how it pulls after the rain in Oklahoma stops. LOL
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Old 04-27-2020, 11:38 PM   #15
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Re: Low power on 2001 6.0

Had to pull my sister-in-laws 19 foot travel trailer home the other day. Truck had trouble getting to 65 mph. Idle was fine. No sputtering or popping just didn't have the power. After I dropped the trailer off I tried to spin the tires. LOL!!! Wouldn't even leave a black mark. I put the code checker (HF) on it. Came up with EGR and MAP? . Also said something about O2 sensors With ? behind it. These cheap code readers with lousy instructions don't help a lot. Any help appreciated.
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Old 04-28-2020, 09:02 AM   #16
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Re: Low power on 2001 6.0

I'm a big fan of troubleshooting.
The code scanners are sometimes useful but they fall on their face when you need sensor data to troubleshoot a problem.

My first step is to take the exact OBD code(s) and google "GM Pxxxx code set criteria". This will tell you what the PCM uses as criteria to set the code(s) in question. Once you know that you have a place to begin looking for the problem.
If you post the codes here it'll help narrow things down. There are an awful lot of codes for MAP, O2, EGR etc so a vague knowledge of the general area the codes were pointing doesn't really help us help you.

This is where a more comprehensive bi-directional diag tool helps a lot.

Can you get a look at live (engine running) fuel trims, MAP, MAF, EGR state, O2 sensor, and other sensors with your existing tool?
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Last edited by hatzie; 04-28-2020 at 09:07 AM.
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Old 04-29-2020, 09:52 PM   #17
rws1012
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Re: Low power on 2001 6.0

Put my code reader back on the truck yesterday. No codes were there. Truck still not running like a 6.0 with 150,000 miles on it should run. Will drive it some more and try to get some codes set. Don't know if it reads while driving. Will check on that. Thanks for replies.
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Old 04-30-2020, 08:37 AM   #18
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Re: Low power on 2001 6.0

Can your scan tool read pending codes?
Torque Pro on an android device with a decent bluetooth OBD interface will allow you to scan while driving.
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RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
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Last edited by hatzie; 04-30-2020 at 08:43 AM.
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Old 04-30-2020, 11:55 AM   #19
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Re: Low power on 2001 6.0

Yes it reads pending codes. There were none showing. Thanks for reply.
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Old 05-02-2020, 07:58 AM   #20
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Re: Low power on 2001 6.0

I googled "GM P0404 Code set Criteria"
This is what I found in one of the first page links.

" In order to know if your EGR’s valve is operating properly, the EGR valve’s feedback system communicates with your Power Control Module (PCM) to let it know if your valve is open, closed, or partially closed at any given time. When P0404 is triggered, it means that the PCM has been told that the valve is performing in a way that is outside of its specified parameters. More specifically, the PCM has been told that the valve is closed when it should be open, or vice-versa."

Bad EGR flow can cause spark knock from higher than normal combustion temps. When this happens the PCM will pull, or retard, ignition timing cutting your performance.

If the PCM is pulling timing because the EGR is sticking and the flow isn't keeping the combustion temps low enough it'll be low on power.

You really need a tool to view items like O2 sensors, Long & Short term fuel trims, knock sensor data, EGR data, and ignition timing advance or retard to properly diagnose this and to prove your fix was successful.

In the good old days the remedy for spark knock was higher octane fuel. You could keep a jug of high test fuel in the bed and run her down to excessively near empty then fill up with some high test fuel and see if she seems to be happier with you. By no means is this a foolproof test but it might tell you something about what's going on.
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RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
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Old 05-03-2020, 12:04 AM   #21
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Re: Low power on 2001 6.0

I appreciate the reply. Very interesting read. My Harbor Freight scan tool did hit on EGR when I started having problems. I pulled EGR and it looked good. Very little carbon. But looks aren't everything. LOL!!! I took my truck on a long drive yesterday and it didn't act very good. Still won't spin those tires. LOL!!! I was in Tulsa traffic and highway driving. It didn't show a "Service Engine Soon" light. Will check with code reader again tomorrow. Thanks again.
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Old 05-31-2020, 03:19 PM   #22
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Re: Low power on 2001 6.0

Update. Took my truck to a shop that can diagnose the troubles I am having. Will get it back Monday hopefully. Will let you know what happened.
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Old 06-02-2020, 11:35 PM   #23
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Re: Low power on 2001 6.0

Got the truck back today. Mechanic said everything fuel , sensors, pressures looked ok. They decided the cat converters were stopped up. Since my muffler has a hole in it I will probably have the whole exhaust replaced and delete the converters. No inspections here in Oklahoma. Thanks for all the replys.
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Old 06-05-2020, 06:46 PM   #24
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Re: Low power on 2001 6.0

Stopped up cats is a not so common issue...

CAT delete will also need ECM changes for O2 sensors etc....

Let us know how you go...
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