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.
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There are many things that could cause this symptom. You would need to start by checking engine codes.
I replaced the throttle body on my 2003 Tahoe. Went for a test drive and reduced engine power light comes on and can’t go over 40 mph. Crud, now what??
Temperature can come into play due to the expansion and contraction effect on the internal workings of the throttle body and other associated parts. If you decide to clean the throttle body Do Not Spray cleaner into the throttle body. Instead spray it on a rag and use the rag to wipe the parts clean.
I have a 2004 Chevy Avalanche 1500 Z71. I recently had reduced power and got the code P1516. I checked all the connections and they are good. My battery tested as bad and needed replaced so I installed a new battery. Still happened after a new battery. The reduced engine power seems to only happen on cold mornings, any known connection to cold weather? My next step is to clean and replace the throttle body if necessary. My question is just why does it only happen in the cold?
-Josh
Two things come to mind. The key and shifter are worn enough that the key can come out of the ignition without the ignition being fully off. When the problem occurs, lift up on the shifter and see if the ignition will turn just a little further before taking the key out. Hopefully the lights will go off. If not the next most likely thing would be a faulty BCM. BCM replacement is a little tricky in that you have to have a Tech 2 scan tool to set up the replacement BCM.