bluebird71

iTrader: (53)

I have an '03 Silverado 5.3 and its throwing a CEL right now, but the only code that shows is for the knock sensors. The motor seems to run ok for the most part, but has become a dog down low! If I floor it from a dead stop, it feels like something is holding it back and it won't even spin the tires. If I give it part throttle, it actually takes off quicker. Is it going into "limp mode" because of the CEL? Do these year trucks even have limp mode?

I changed the plugs in it a few months ago (pre-gapped factory AC Delco plugs) as well as new plug wires and didn't have any issues. I also recently changed the fuel filter. The only other issue is the A/C compressor on its way out. It runs kind of rough at idle with the compressor on, but has gotten a little rougher on its own in recent weeks even when the A/C is off. No codes for cylinder banks or anything, just the knock sensors. I noticed the other day that the wire harness coming off the knock sensors looks frayed, like maybe something chewed on it.

My overall question is, would a bad knock sensor and/or knock sensor harness actually make the motor run poorly and/or go into limp mode or is there a bigger issue here?

marineusmc4

in your information center does it say "Reduced Engine Power"? Mine was doing this and all I had was a MAF code. but yes they do have a "limp mode", thats what the "reduced engine power" is

bluebird71

iTrader: (53)

Where would it say that? Would it say that in the dash somewhere or would it be a code on a scanner? I don't see anything like that coming up immediately on the dash.

marineusmc4

it will say that on the instrument cluster in the information center where ur mileage, trip meter, and hourmeter are. assuming its digital. if you could take a pic of ur instrument cluster ill tell u exactly where it is. but since u have an '03 which is the same as mine then we prolly have the same instrument cluster

marineusmc4

if ur knock sensor isnt detecting any knocks then i would assume that it wouldnt cause your engine to run poorly. im suspecting if u have any codes for a knock sensor it is a high or low circuit which could mean a loose or dirty connection, a short or open wire, or a bad knock sensor. if u have a scanner that can detect knocks then u can see if the knock sensor is detecting any knocks and if it does then u know ur knock sensor is good but then u have to figure out what is causing the knock.

bluebird71

iTrader: (53)

I swapped in the Escalade cluster. Not sure if that really matters or not though. I still see the "oil change due" prompt when I first start it if I haven't reset it.

bluebird71

iTrader: (53)

Mine doesn't actually say "reduced power" anywhere, but its a slug if you slam the gas from a stop. It's not as noticeable if your already moving and still kicks down to pass and everything. If you slam the gas from a stop though, it barely goes anywhere. I almost got hit turning the other day because of it. If you give it part throttle from a dead stop though, it takes off quicker, just as it would normally at part throttle.

Suburbazine

This is a terrible assumption. You know what the say about how you spell assume, right? It makes an *** out of U and ME.

In this case, you are woefully incorrect. If for ANY reason a code relating to a knock sensor sets, the truck immediately enables the most conservative timing settings possible, resulting in the engine being a dog off the line and running like crap.

Since you have knock sensor codes, these engines are TERRIBLE about getting water under the intake manifold and corroding the sensors. The OP's sensors will be needing a replacement. The intake manifold has to come off with is a 2 hour job, you need 2 new sensors, a new sensor harness and new intake gaskets. Parts will come to roughly $180.

marineusmc4

if im wrong all you have to say is im wrong, not be a ******** about it...notice i didnt say "yes, thats the problem", or "no, thats not the problem?"...hmmmm

this is exactly what happened to my truck, yet i had 0 knock sensor related codes.....did u not read what i posted earlier?????!

bluebird71

iTrader: (53)

I have 2 spare sensors and a harness waiting to be installed. I'll go ahead and do that I guess and see what happens. The sensors and harness came out of a very low mile LS1 I had a few years ago and still look new. I looked up part #'s and they all seemed to match so I don't see any reason to buy all new stuff to put in unless there is something I don't know.