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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Just to confirm we are on the same page. You have 0 volts on the Purple 5 volt reference wire at terminal “B” of the C2 connector at the TAC module and you have 7 volts at the Tan wire, terminal “D” of the C2 connector at the TAC module?
I have a 2003 Tahoe with reduced engine power and codes P1518 and P1125. I have replace throttle body and pigtail, APP sensor, battery and checked ground wire extensively. I ran some tests and found that my TAC module is providing 5 volts to APP sensor 1 but is providing 0 volts to APP sensor 2. I checked this directly out of the TAC module not through the wire harness, bought a new TAC and got the same results. My ground circuit for APP sensor 2 is also low at 7 volts with KOEO. APP sensor 1 volts check out fine. What is my next step?
Multiport and throttle body fuel injection systems both have throttle body assemblies. With the “Reduced Engine Power” message, you have an electronic throttle body assembly and need to check the codes and diagnose appropriately.
Hi I’ve got a 2003 Taheo 5.3 liter with a multiport fuel injector not a throttle body with the same reduced engine power problem, could there be another problem?
You just did. What kind of vehicle and issue do you have?