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”
Share Your Experience:
You must be logged in to post a comment.
Replacing the throttle body will not correct a code P1125. It is an APP sensor code. In theory the problem should be the APP sensor (gas pedal), the TAC module and the wiring in between. The vent problem is likely due to an interrupted recalibration after a battery disconnect or a faulty mode actuator. Please the “Recalibration” label on the left side bar of the site.
after replacing the harness on the throttle body i was hoping it would fixed my reduce engine speed issue i keep getting a p1125 code already replaced the pedal actuator sensor.
next im attempting to change out the throttle body.. but now i have another issue after replacing the harness. when i did the test drive to see if the reduce engine speed would go away i encountered an issue with my a/c front vent not working. the a/c only blows thru the defrost even tho the knob is turned to the front vents. maybe i blew a fuse? any suggestions
Although they could be separate issues, it is quite likely that the P0101, P0171 and P0174 have been induced by the throttle body situation. Dependent on the depth of tooling, your mechanical ability and the amount of time you want to invest into this problem, my suggestion would be to check the integrity of the ground at the passenger,top rear of the engine block and then replace the throttle body assembly with a a new AC Delco part.
Hi Sparky,
We just got home from our family vacation. We took my daily driver…a 2005 Chevy Tahoe, and it experienced for the first time the “reduced engine speed” while driving through the Nevada desert. We were able to stop several times, and limp it home. When we hooked it up to the scanner, these are the codes we had. P0171, p0101, p0174, p1516, and p2101. They all seem to be related to throttle body assembly. Any suggestions are appreciated. I drive many highway miles with my two young children, and I need to be get this resolved. Thank you, Sparky!
As it turns out, the diagnostic instructions I have misrepresent terminals “B” and “D”, they are reversed. Therefore, even the new TAC module did not test out correctly. When I saw bad results with the new module I put the old one back in to continue diagnostics without even test running the new TAC. After you “confirmed we were on the same page”, I notice the discrepancy, retested the correct terminals and both TACs tested fine. I put the new TAC back in and am test driving it for a few days. The accelerator operates much more smoothly and no codes. Evidently my TAC was bad. Thank you for being thorough and questioning my moves.