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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The “coolant issue” you speak of has absolutely no relationship to your problem. More than likely the battery is faulty and you have damaged the throttle body assembly by repeated crank attempts with low voltage. Start by having the battery checked. Replace it, if it is found to be faulty. Then hope and pray that the throttle body is okay when you restart with a good battery.
Having similar issue with 2003 tahoe, 90,000 miles. First presented as dead battery which took two vehicles to jump. Drove for 30 min to help build charge. Next day, dead battery. Charged all day with charger and ran again to help recharge. Ran to store, shopped for 30 min. Truck dead but with pedal pump I get it to crank. Then the engine sounded very scary along with engine light and reduced engine power message. Was afraid to turn off due to battery. Temp was at 210 at start. I poured water into overflow tank. (After last LOF, they refilled with straight coolant.) I attempt to drive in parking lot and realize extreme loss of power. I turn off and restart, after second time, message cleared but engine light still on. I make it home and husband attempts to start. It struggles to start and now battery dead again. Wonder how much water and coolant may have played a part. It seems that engine coolant straight is too “thick”. Any relation to other issues listed here?
I am assuming you meant a 2003 Trailblazer. Speaking from experience in diagnosing the TAC systems, there are so many redundant controls and failsafes built into the systems that it is virtually impossible for that to happen. You would need to speak to someone in GM engineering to get all of the technical details on this subject.
I am investigating a case where the throttle body was replaced on a 2003 Chev Blaz due to RMP idle issues +/-, worse when A/C is on. Setting code 1516 for TAC module. Symptoms were resolved with replacement. Six months later, driver alleges that vehicle suddenly accelerated (while driving up their driveway) and knocked their home off the foundation. Possible acceleration due to improper throttle body replacement 6 months prior? I have also requested the EDR information to rule out human error/intentional action. Any comments or thoughts?
Luckily yours sounds like you just need to have the throttle plate cleaned at this time. If the throttle body was faulty it would not open when you depress the APP sensor (gas pedal).