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 ground wire for the TAC system is in the same location as the broken wire in the following repair post. You will need to copy and paste the address.
http://www.sparkys-answers.com/2011/08/2003-chevrolet-avalanche-no-run.html
To clean the throttle body you will need throttle body cleaner, protective gloves, a shop rag and basic tools. Remove the intake hose between the MAF and the throttle body. Use a screw driver handle to hold the throttle plate open. Spray the throttle body cleaner on your rag and wipe the bore clean where the throttle plate seals. Clean the throttle plate edges. You will need to switch the location of the screw driver handle to clean the other half. Make sure the key is OFF during the cleaning process and DO NOT spray throttle body cleaner directly into the throttle body.
I searched around and was looking for a couple specifics on the Reduced Engine Power error. I am getting it randomly and after checking and cleaning up several connections and locating a vacumn leak it seems to have gone away for at least the last couple of days. The odd thing is that now I have a very low idle which I did not have before, but I think maybe it was compensating for the air leak I found.
Could you email me or post the following?
Location of the ground wire you mentioned in a couple posts on the rear of the engine block.
Proper way to clean out the throttle body. Thinking it might be the cause of the now low idle.
Thanks in advance your information is superior to anything I have read so far.
John
Check the ground wire at the passenger rear of the engine. many times it will be broken inside the insulation or just have one or two strands hanging on.
We are having the same issue p1518, in non mechanic terms what are the next steps we should take, we replaced the.throttle body and no luck, desperate for help
The code P1518 is for a serial data fault between the PCM and the TAC. There could be an actual communication fault or the fault could be caused by a TAC that does not have the proper power and ground supply to work. If it does not work it cannot communicate.