Reduced power mode

Tiny
FLYBOY69
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 145,000 MILES
I own a 2003 Chevrolet 2500HD, with the 6.0l engine. During the summer time I do not have many problems with it, but when the weather starts getting cold it will run for 10 to 15 mins then go into reduced power mode. I have changed out the water pump and the thermostat. What do you think is wrong with it?
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Friday, December 24th, 2010 AT 2:25 AM

59 Replies

Tiny
FACTORYJACK
  • EXPERT
Typically, what triggers the system to go into limp home(reduced power) is a fault that relates to the throttle actuator or accelerator pedal position assembly. Ideally, you should seek the trouble code that is associated with it. One crucial concern, is does it have any aftermarket stuff installed? There may be a bulletin that states(depending on the code) the throttle body or body connector could be cause, and it could be. I have seen instances where this was followed, only to have the fault reoccur, and it eventually was ruled to aftermarket installations into critical circuits. The electronic throttle is run on 5 volt potential, so some resistance that would go unnoticed in a 12 volt circuit, causes intermittent problems in a 5 volt circuit.
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Friday, December 24th, 2010 AT 3:43 AM
Tiny
FLYBOY69
  • MEMBER
There are no after market items on the engine. I will get a code readerand post that in a few days.
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Friday, December 24th, 2010 AT 4:54 PM
Tiny
FLYBOY69
  • MEMBER
Okay, I got a scanner and the two codes that are popping are P1516 & P0171. Should I remove and replace the throttle body or is there a check that I can do before I go out and spend $200.00 for that part? Thank you for your help!
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Friday, January 7th, 2011 AT 7:19 PM
Tiny
FACTORYJACK
  • EXPERT
The P0171 is a lean code for one bank of cylinders. It would not result in a reduced power message. I would clear it and see if it returns over time. The P1516 will result in reduced power. There is a bulletin I included for reference, may or may not apply, but gives a starting point.

#PIP3089B: SES Light And Reduced Engine Power DTC P0120 P0220 P1516 P2135 - keywords accelerator actuator APP blade body connector connection DTC L33 L59 LH6 LR4 LM7 LS1 LS2 LQ4 LQ9 module position reduce sensor - (Oct 31, 2006)

Subject: SES Light and Reduced Engine Power DTC P0120 P0220 P1516 P2135

Models: 2004-2006 Buick Rainer

2005-2006 Cadillac CTS-V

2003-2006 Cadillac Escalade

2003-2006 Chevrolet Avalanche, Corvette, Express, Monte Carlo, Silverado, SSR, Suburban, Tahoe, Trailblazer

2003-2006 GMC Envoy, Savana, Sierra, Yukon

2003-2006 Hummer H2

2005-2006 Pontiac GTO

Equipped with a 4.8 5.3 6.0 or 7.0 V-8 Engine

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A vehicle may be brought into the dealer for a reduced power message, and DTCs P0120, P0220, P1516, P2101, or P2135.

The Throttle Actuator Control (TAC) / throttle body type trouble codes, may be caused by a loose wiring crimp at the throttle body connector, or a broken throttle body circuit.

Recommendation/Instructions:
Complete the current SI diagnostics for any symptoms or trouble codes found. If a intermittent T/P or TAC module type code is occurring complete the inspections below.

Inspect all related throttle body terminals for a loose wiring crimp. The loose crimp may be difficult to find, and the poor connection will be between the terminal and the copper strands of the wire. Wiggle test the individual throttle body circuits to see if the concern can be duplicated.
Inspect the related circuits for broken wires inside the insulation. The outer wire insulation may look fine, but the internal copper strands may be partially broken. Breaks in the wires usually occur within 1 to 4 inches of the throttle body connector. Wiggle testing may also induce a trouble code to set.
On C/K trucks complete SI procedures for voltage drop on grounds G103 and G104. Grounds G103 or G104 may be loose or corroded.
If a terminal crimp or a broken wire has been found, repair or replace only the circuits involved. There is a throttle body pigtail connector available through GMSPO, but installing this pigtail connector may cause other intermittent TAC module/TP codes at a later date. If this pigtail must be used, please follow the SI procedures for Splicing Copper Wire Using Splice Sleeves. (The proper Kent-Moore crimping tool must be used for this repair).

The test chart for that code involves some circuit testing, and may be most streamlined with a scan tool that can display data. Often times this code can be hard to duplicate. If I were to start somewhere, it would be splicing a new connector at the throttle body.
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Sunday, January 9th, 2011 AT 3:58 AM
Tiny
CHIEF_FL
  • MEMBER
I had the same problem and found two broken wires 3/4" from the throttle body plug. Two butt connectors and back in business.
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Tuesday, June 19th, 2012 AT 1:23 PM
Tiny
RIVERMIKERAT
  • MEMBER
Thanks for the heads up Chief_FI.

Flyboy did you ever get this diagnosed and fixed, or do we need to do more testing and diagnosing?
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Monday, July 30th, 2012 AT 3:52 AM
Tiny
LARRY@888CARHELP.COM
  • MEMBER
My 2003 Silverado 2500HD 6.0 has a "service brake booster? Message in the DIC - how can I reset it? I don't believe there is a problem as everything works great! Thanks for your help.
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Monday, January 29th, 2018 AT 12:07 PM
Tiny
KEN
  • ADMIN
Please post your question here

https://www.2carpros.com/questions/new

Cheers, Ken
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Friday, February 2nd, 2018 AT 1:44 PM
Tiny
JMOONEYH
  • MEMBER
  • CHEVROLET SILVERADO
2003 Chevy Silverado 49,000 miles. Went to start the truck in the morning and the reduced engine power warning came on in the DIC. Manual says it comes on due to overheating and enters coolant protection mode. When I press the gas the truck will not accelerate. How does it have a overheating problem sitting overnite and how do I get it to a garage if it only idles down the road? Is there a reset button so I can at least drive it?
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
SC1 RACING
  • MEMBER
Did you check coolant level?
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
JENNIFERG
  • MEMBER
Had the same problem with my 05 Z71. Took it to the Chevy dealership and turns out it was a broke wire. Auto Zone scanners wouldnt read it when I took it there due to a blown fuse. Have someone check all the wiring before you spend mega bucks.
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
GRCROOKSJR
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 123,500 MILES
If while cranking I get a 1 second stutter I get the above codes but if the cranking continues normally it then starts and runs fine. I've cleaned the ground under the driver, checked the ohms at the TPS and accelerator, did the tug test and checked for corrosion on the TPS connector, checked the wires in the fuse box (left fender), cleaned and charged battery, and checked and cleaned the throttle plate.
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
HMAC300
  • EXPERT
Check your ect sensor might be part of problem and check for broken wire
at throttle body and firewall it rubs on there and wears through. It'a blue and white wire. You may need to replace the throttle body as well which is pricey. Also check the ground wire at back of lh head and give a tug the eyelet likes to break there just a soft tug will do it.
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
GRCROOKSJR
  • MEMBER
How do I test the ECT?
Is there any test on the throttle body?
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
HMAC300
  • EXPERT
On chart in pic one side is temp and other is ohms so check it that way lh side is temp. See pic for other app is the gas pedal
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
GRCROOKSJR
  • MEMBER
I did find cracked insulation on a gray or brown wire in a harness between the fuse box (left fender) and a 3 x 4" black box mounted on the firewall. When I tugged on it it parted so I spliced it with crimp style connectors reset the codes and drove it for 25 miles. So far so good. Thanks for the help, I'll get back to you if it reoccurs soon.
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
HMAC300
  • EXPERT
The crimp style connectors should never be used on vehicles now a days. You should only use solder type connections with shrink tube to protect them. Glad you found the problem.
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
DANIELS16
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
At highway (55 and up) speeds the reduced engine power reading comes on and shuts down my power.I have to pull to the side of the road shut off the truck, wait 10 seconds, then it'll start back up normal. The U0107 code appears stating loss communication with throttle actuator control.I have replaced the wiring harness and throttle position sensor as I heard this may be the problem. I have also cleaned the throttle body. Neither seemed to work. What could this be?
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
HMAC300
  • EXPERT
Tht is the throttle control module-gas pedal in laymens terms. Check battery for condition as this can cause it also do a load test. Tire stores auto parts do for free. Then see if terminal ends are corroded on gaspedal if you are in the winter climates. You shold also get it scanned first too to see if other codes are set as they may set this one. Finally check gas peadal to see if it is shorted out or not sending correct voltage to pcm.
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)
Tiny
DANIELS16
  • MEMBER
The only other code showing up is show loss of communication with electronic brake control module which I don't think should have to do with the throttle actuator control. And the terminals on the battery are clean
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Saturday, December 8th, 2018 AT 11:37 AM (Merged)

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