2003 Chevrolet Silverado - Reduced En...

Sand Springs, OK

#103 Aug 23, 2010
I'll put my money on the purple wire. I recently replaced the terminal on that one and the problem is gone. 1500 miles without reduced engine power!
Shawn_P wrote:
Thanks everyone for their input. It saved me a lot of money.
Reduced Engine Power, 2003 Silverado Z71 1500.
Trouble cleared after disconnecting and reconnecting the plug closest to the driver's fender, at the electronic module mounted to the firewall right below the cowl. The other plug goes to the foot feed.
After looking over the web, I would encourage you to examine your wiring very thoroughly. DO NOT replace any components without a written guarantee they will refund ALL your money when the problem reoccurs.
Use an ohm meter, 24 gauge wire and at least one lead with a "telco clip", with a "bed of nails". The bed of nails penetrates the insulation and the small wire on the other lead of the meter can be poked in the connectors to check for continuity.
Most of the reports I found indicated broken conductors or bad crimps on the pins/sockets. The broken conductors were within 2 inches of the connectors, so put the bed of nails as far from the connector as you can get with out completely trashing the wire loom. Wiggle, pull, and push each wire and verify your meter stays below 10 ohms so, zero is fine. I'd say anything above 10 ohms you should double check.
First, squeeze the "bed of nails" with a little more pressure. If they are new, they will connect fairly easily.
I was sure my trouble was a connection/broken wire. I parked the truck, never having the problem. Then noticed the message when I turned the key on, w/o trying to start the truck. I needed to roll the truck back a bit, I had two young raccoons in the engine compartment and could not open the hood because of a shelf.
I thought the message was because the key was on the engine was not running, but after starting it I figured out it was not. I studied this forum and spent about 2 hours checking connections.
I intend to figure out which wire causes this condition. I think it would be a great theft deterrent/ vehicle saver. Put the truck in 4 low and reduced engine power while parked at a hotel. Thieves probably will abandon it quickly.

Mechanic Falls, ME

#104 Sep 8, 2010
I had the same problem.

The "low coolant level" light had been on for about 3 weeks before I finally got around to adding fluid. The full indicator line was difficult to read, so I only added a little. The light went away, so I thought 'problem solved'.

A few weeks went by, and tonight, I started up my truck (while it was still hot as I had just shut the truck off a few minutes prior) and it said "reduced engine power". I disconnected the battery and reconnected it and the "reduced engine power" light was gone, but the check engine light remained.

After reading some of the posts above, I decided to add more coolant, do the battery thing (because these were the easiest options at 10PM) and to my surprise, the check engine light disappeared!!
my headache

Jefferson, GA

#105 Sep 9, 2010
My 2003 2500 6.0 started the rep syndrome in Sept 09, would only do the rep thing when it rained.
mechanic replaced the throttle body sensors, battery,throttle body...still the rep would happen(started not to matter if it was raining or not). Well all this part swapping that the guy was doing had already cost like 1500.00, and the rep was still there, never knew when to expect it 30 mph or 80 mph(never if the truck was in cruise mode).
It did it so many times that I wore out both battery terminals because I would remove the bolts to clear the freaking rep problem.
This happened yesterday 9 yes 9 times before I could drive home from work and I live 10 miles from my work, started thinking about if my insurance policy included fire protection.
Found some info online last night that may help and I think I go it sorted out this afternoon.I was backing out of my spot at work and the rep kicked in before the truck moved 10 feet, did the battery cable removal agian, went maybe 100 yards, same as yesterday and rep happened a 2nd time.
This time I opened the hood and tapped on the cable connector at the throttle body, just tapped on it.
Drove the thing 40 miles and it never did it agian until I went down a bumpy dirt road kinda fast,just seeing if things in that connector would get loose agian, and they did.(it has little pins in it that hold it to the throttlebody)
GM has some tech notes out about this problem and that is what got me to suspect the connectors at the throttlebody, alot of their vehicles from 2003 to 2006 are having this problem.
GM has a pigtail type replacement end for the throttlebody connector that is supposed to cure it, just go on their site and type reducedenginepower and you will see the bulletin, not a recall just a bulletin.

Grand Rapids, MI

#107 Sep 15, 2010
i have 2004 chevy silverado 2500 hd with 6.0 i just had reduced engine power come on throttle position circut b poor gas milage 10.2 mpg


#108 Sep 27, 2010
I was just wondering if u had cheked ur alternator belt ? I havé thé sabe problème With m'y gm car so mabe thats thé reason bdw its a pontiac pusuit 4 door and they havé recalled power sterings and more go to gm dealer

Hindman, KY

#109 Sep 27, 2010
we have a 2003 silverodo that when you go out to start some times won't start on first turn. put it on machine said everything is fine. told us to change gas filter did this and run good for about 2 weeks now doing it again . any one know what could be wrong with it

San Jose, CA

#110 Sep 28, 2010
help wrote:
we have a 2003 silverodo that when you go out to start some times won't start on first turn. put it on machine said everything is fine. told us to change gas filter did this and run good for about 2 weeks now doing it again . any one know what could be wrong with it
Check the wires going to the plug on the throttle body. My truck was having the same problems and we found three of the eight wires were bad. We sliced them together and that fixed it.

Hindman, KY

#111 Sep 29, 2010
thanks chris i will have him check it.

United States

#112 Oct 7, 2010
where is the idle control located for 03 2500hd 6.0

Juneau, AK

#113 Oct 11, 2010
I have a 2001 with 21,000 miles on it. The battery was dead and after jumping it the check engine light and the reduced engine power light came on. The truck inches along on its own idling power. When I press on the gas pedal nothing happens. Has anyone had this problem or any suggestions. I live in Juneau and the closest dealership is 600 miles.


#114 Oct 13, 2010
kristy wrote:
Hello, my name Is Kristy, and I am curious to see how you were able to resolve this problem with your truck. My father has a 2500 HD Silverado, 2003 model. He is experiencing the same thing with his "reduce engine power" light coming on. If you would, please help us out with this delima we are having. Thank you so much!!!
I have the exact same truck and by process of elimination I had to replace both knock sensors and the knock sensor wire harness, the throttle position sensor (the gas pedal), and the throttle body all this fixed my truck and it has been 5 months and no problem.

Pittsburgh, PA

#115 Oct 23, 2010
2003-04 instrument clusters are pron to fail. they will give false messages and some gauges will stop working. try exchanging the cluster. it is an easy job. 5-10 min try to find a 05-06 cluster used.

United States

#116 Nov 2, 2010
The problem is in the wiring coming from the app sensor. Check the connection plugins

Albany, GA

#117 Nov 8, 2010
My 2500 hd 2003, has went to reduced enigine power and even to the extent that the engine completely dies, or the truck is running and rolling in reduced power and the steering locks up and the brakes dont wont. Tried: air filters, air flow sensor, two throttle positioning sensors, connectors with not much success.
joey b

Dayton, OH

#118 Nov 10, 2010
Rich wrote:
I have a 2003 Chevy silverado HD. I am having idle problems. the truck runs great except for when I come to a stop. When I press the brakes to stop the truck wants to die out. Any suggestions?
if you have a "drive by wire" set up..try cleaning your throttle plates

Estevan, Canada

#119 Nov 20, 2010
I have an 2003 Chevy 1500HD with a 6.0 motor, been chasing this "reduced Engne Power " light for a few years now,, my local Performance shop told me,, Your Cats are getting plugged and when they get hot the reduced engine power will come on. Only option they said was replace them, or get a custom tune for the truck and reflash the computer. I got the custom tune for my Diablo tuner , shut off the rear O2 sensor, cleaned the cats out and now been 5 months since i have seen the reduced power light come on,, And with the cats gone and new tune, have increased my fuel mileage by 2-3 mpg now and more power
barb t

Pittsburgh, PA

#120 Nov 21, 2010
My son has a 2003 1500 with the engine light on. Had it to mechanic twice - they replaced the mass air flow sensor - light went out - now it's back on. The rpms increase when I put my foot on the brake as well - all of this before the engine is up to operating temperature. RPMs high when I start up first thing in the morning - drove 6 blocks the other day without every stepping on the gas. Feels like gears are slipping but I am not sure if that is it or if the engine is surging. Any ideas?

Plainfield, IN

#121 Nov 23, 2010
Rich wrote:
I have a 2003 Chevy silverado HD. I am having idle problems. the truck runs great except for when I come to a stop. When I press the brakes to stop the truck wants to die out. Any suggestions?
Having the same problem with my 2003, pull up to stop and the engine rpm hunts and will die..


#122 Nov 23, 2010
I have 2003 avalanche 5.3l. The truck runs good, until u get the rpms past 4500-5000, then bang REDUCED ENGINE POWER AND ENGINE LIGHT. So have to pull over and wait a minute and it restarts with no rep light. After a restart the truck about 3 times the engine light is gone. As long as i dont slam on the gas i am fine, but that sucks. The computer pulls a code p-1518 which says electronic throttle module to pcm commuication. Could be sensor or connection, still have to figure out!

Salisbury, MD

#123 Nov 25, 2010
When my truck (04' 2500 Silverado) did that I replaced the whole Gas pedal. The pedal comes with the sensor and the sensor is calibrated to the the pedal so do not buy just the sensor or it will not work. I made that mistake and my accelator kept accelatoring on its own. It only cost about 125.00 and takes about 20 minutes to replace it yourself. Two bolts and a wire is all there is to it. I hope this helps you.
kristy wrote:
<quoted text>
Hello, my name is Kristy, and I was curious to see how you were able to fix the problem with this situation. My father has a 2500 HD Silverado 2003 model. He is experiencing the same thing with with his "reduce engine power" light coming on. If you would please help us out with this delima we are having. thank you so much!

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