Reduced Power Displayed 2003 Chevrolet Tahoe

This 2003 Chevrolet Tahoe with a 5.3 liter engine came in with the customer complaint of the reduced power display was on and the vehicle could not be driven more than about 30 mph. Checking codes found a code p1516 stored for Predicted VS. Actual Throttle Position Correlation Error. That is fancy computer talk for the computer expects the TPS to be in one position and it sees the TPS in another position. There are several things that can cause this condition but by far the most common is a faulty throttle body assembly. I have noticed a disturbing trend in these vehicles in that the last few that I have had to change I also found very weak batteries and the weaker the battery is during cranking the more pronounced the symptom. If the key was left on in these vehicles for more than about five to ten minutes (the time it takes to hook up a scanner and check computer codes and relative data), the starter would turn the engine over very slowly (indicating a weak battery) and sometimes the battery would have to be jumped to start the engine. I may be wrong but it is my belief that a weak battery condition during cranking may be leading to premature failure of the throttle body assembly. My personal philosophy on late model highly computerized vehicles is to replace the battery every three to five years regardless and of course use a good battery and not the cheapest you can find.

Anyways on to changing the throttle body assembly. First remove the upper engine trim cover by first removing the screw and lift off.

Next remove the intake tube that connects to the mass air flow sensor.

Now the intake hose from the throttle body assembly.

Disconnect the clip that holds the intake hose assembly to the radiator hose.

Remove the harness connector from the throttle body by first pulling the gray locking clip back. Depress the lever and remove the connector. Inspect the yellow wire for possible damage as it too can cause the problem, although it seems to be more of a problem in the full sized vans.

There are three nuts that have to be removed.

Next the coolant lines have to come off but first I clamped them both off with hose clamp pliers. Then I took the coolant hose spring clamp and moved it back down the hose so that I could remove the hose from the throttle body. One could use pliers with a little luck and a lot of frustration it will move.

After the hose, next to the alternator is removed the throttle body can be repositioned to make the rest of the job easier.

Off with the old and on with the new. First the passenger side hose is installed. Then the throttle body assembly is put back in place and the driver’s side hose is reattached. In the following picture you can see that I used two pair of hose clamp pliers for the job. It saves having to drain the coolant system and time is money.

Now it is time to put the hose clamp back in place.

The new throttle body is now installed and ready for the intake hose and top trim cover to be replaced.

173 discussions on “Reduced Power Displayed 2003 Chevrolet Tahoe”

  1. Sparky, I have a 2003 Chevy Suburban with the 5.3L. I’ve had the reduced engine power illuminate at multiple random times. I took it to the shop and they told me (for $150) that my intake manifold was leaking. I used starter fluid around to intake manifold to see if the shop was giving me good data. However, nothing happened. I do have “Bank 1/Bank 2 Too Lean” codes. I’ve cleaned throttle body, MAF sensor, added seafoam to gas tank. It randomly continues to tell me “reduced engine power”. I usually just have to stop and turn the engine ON/OFF a few times & then it clears for another few days. Any advice? I live in Kodiak & have very little choice in car repair facilities.

  3. Ok, So I wanted to report what I did and the result so far.

    I had already planned to replace the air filter and oil and filter so I did that first. Next I pulled the main connector everyone talks about on the throttle body and took it apart, checked for any loose wires, none apparent, and then added some dielectric grease. Did the same for the 2 big connectors under the hood on the driver side firewall and also removed the negative battery cable and added some there.

    Next I checked the ground wire that mounts to the back of the block on the passenger side and it was fine and solid.

    Next I remove the parts to do the throttle body cleaning, it was pretty black around the edges and inside so I cleaned it well with a rag and cleaner.

    Got everything sealed back up, neg cable back on and started up and not only was the Reduced Engine Power message off but so was the check engine light. I bought this used so the check engine light has been on the full 3 years I have owned it. After starting a few different times and driving over 200 miles I still have no warning lights or messages…

    I did find a vacumn line/rubber boot that was broke and really hissing. I took it off and taped it up with electrical tape for now and will replace it soon. As soon as I did this the idle changed. Out of the stuff I have done I was curious if you see anything familiar that might convince you I have seen the last of my reduced engine power warning? I still haven’t seen that message yet but my check engine light did come back on, but as I mentioned before it has always been on.

    Thanks again, much appreciated to you and all that contribute to the site.

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