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”
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This is an added comment to the Dec. 3 3:32 post. The error code that is coming up is p1518. Still need to check that ground wire though.
A trouble code would be good if possible. Without a trouble code the only two things that I could recommend is checking for a power ground on the top rear of the engine, passenger side I think. The wire will sometimes break where it connected to the ring terminal. Also a possibility That one of the wires at the throttle body plug is broken internally. most references are to the yellow wire. A gentle wiggling may bring it back temporarily.
I have a 2003 Chevy Tahoe. Started having a problem with the “reduced engine power” about 4 months ago. Had the Throttle Body cleaned by a mechanic who was telling me that the codes that is was pulling were “vague”. Fixed for about 2 weeks and then I would have an occasional problem. Reduced engine came back full force last week and would show the error when I started it. With your directions:), changed the Throttle Body and put in a brand new battery. It’s 24 hours later and I am still getting the “reduced engine power” error again. What are your thoughts?
On older, pre OBD2 vehicles you could jumper the diagnostic connector terminals and count the flashes of the check engine light. Not possible any more and could cause other problems.
A long slow charge is better and it should not matter which set of terminals you connect to, top or side.
There is no mechanical downside to a full antifreeze concentration. There are thermal and corrosion issues with full strength however.
Thank you for your response!
Battery is relatively new, 3 years. i will check all terminals. this also has side and top posts, any preference for charging? at this moment, car cranks but with error message.
Any way to “jimmy rig” DLC for display codes? No access to pinned connector. Internet is dangerous for ideas.. saw a post about inserting paperclip into terminal and watch for flashing display lights. Tempting!!!
Any mechanical relevance period to full coolant vs. diluted coolant? I ask from a previous overheating issue that seemed to be rectified by replacing coolant with water.
Mechanics day before holiday not so easy to come by, lucky we have another car for our travels.
Have a happy and peaceful holiday. Love this site.