I'm taking "Reduced Engine Power" to mean low voltage. Provided all your connections are ok, are you absolutely sure your battery is good?? If your truck is an 03' and you're on the original I would go ahead and try a new one before dropping your gas tank.

 

What jmproductions stated is accurate... Reduced Engine Power is related to low voltage. Does the starter even turn? The clatter sound you may be hearing is the clatter of the starter solenoid attempting to engage the starter gear to the flexplate.

Check your underhood chasis grounds. Improper grounds will restrict electrical current flow. No current flow = no power thru electrical system. You may save yourself from being charged $60 from GM Service... that's after you have it towed to the dealer ($100).

Good luck!

 

Linda,

Just saw this thread. Sounds to me like an electrical problem, a bit hard to diagnose remotely, but here are some things to try.

Disconnect the fuel pump, and see if the relay still chatters. If it stops chattering then I would check the pump, wiring, and especially the ground connections. The other possibility is, as Evil pointed out, a clogged fuel filter or other restriction in the fuel system which could overload the pump, or a faulty pump regulator. If it contiues to chatter, then there is an issue with the electrical system somewhere. I would get a meter and start checking things out. If you aren't familiar with things electrical, get someone to help you.

I just checked my owner's manual on the "Reduced Engine Power" message, and at least for my truck it indicates a protection mode the pcm goes into when the engine is overheating. This mode causes the engine to run in 4 cylinder mode, alternating between banks (that would reduce power all right). Since you are not overheating, this points even more so towards an electrical problem, most likely a faulty ground or loose connector somewhere, perhaps from the blower installation. I would go through the electrical system with a fine tooth comb, looking for loose connectors and bad grounds. Especially check the ground between the engine and body, and the pcm and body. Wish I was there to help.

 

Manual says to check a ground on rear of left cylinder head if certain DTCs are set.

Do you know what DTCs are set? That should identify the problem that initiated REP. From personal experience, REP mode usually is initiated when the PCM receives conflicting data. e.g. measured airflow does not match predicted airflow, throttle position sensors 1 & 2 are in disagreement. Could be a DBW wiring issue, TAC module issue, tuning issue if a change was made to the tune, air leak after the MAF, sensor issue, etc. Happened to me when my TB electrical connector got wet. I think REP is suppposed to clear on its own if the ignition is turned off for a minute or so. If it resets, then the issue is still there.

**Fuel pump and relay should not be energized for more than a few seconds with the ignition in RUN and the engine off. Something is going on with that circuit/wiring if it did the same thing with another relay. I would check that out prior to dropping the tank.

 

pretty sure its not the filter, i changed that when i installed the blower

I didnt check battery voltage, but that would not explain why the fuel pump relay is chattering like crazy. I will throw a meter on it tomorrow and see what it is for sure

Definately NOT the soleniod, its definately the relay in the underhood fuse panel. And no, the starter does not even turn.

I will try to disconnect the fuel pump,to see if the problem goes away, but i dont think i can get to it without lowering the tank. I did not make any electrical changes (other than extending the throttle body harness and alternator harness) when i installed the blower. All of those connections were done with solder and ran in wire loom.....so i know its not any of those. No PCM modifications were made.


No, i dont know what code was set, i dont have a scan tool. I will go and check all grounds to be sure, but i have a feeling its something in the fuel pump circuit because the relay (and any relay i try to replace it with) continues to chatter well after the pressure is up. It should only be trying to send voltage to the pump for a few seconds (like you said), but it will continue to chatter until the key is turned back to off or Acc. Still dont understand why the starter will not even crank...

 

Must be a ground wire that came loose or shorted battery. Check those first then move towards a shorted fuel pump.

Jim

 

My brother's truck said the same thing R E P so we took it to autozone and something about TPS came out, so we changed throttle body and that R E P light went away.

 

If that starter isn't turning, have the battery checked first, then inspect chasis ground connections. For piece of mind, remove, clean, and reinstall. Take battery to A-zone for a load test. A normal 12V check (with a DMM) on an unloaded battery means nada when dead cells exist.

When does the chatter occur, when the switch is in the RUN or CRANK position?

 

Would be nice if you could borrow a code reader from somewhere. More diagnostic info here. Some of this (e.g pcm, ignition switch) could be related to both problems.

 

New battery installed, did not solve the problem. Battery (old and new) display 12.6 - 12.9vdc at rest, when the key is turned to run position the relay chatter starts, and voltage drops down to 10.2vdc. I could find no ground issues anywhere, and i removed and inspected all fuses in both panels. I bought an AutoZone scan tool and it read clean, no codes present. I guess my next step is to try and unplug the harness at the gas tank to see if that makes the chatter stop.

STILL DONT KNOW WHY IT WILL NOT EVEN CRANK OVER!
I cant find an answer to that anywhere......