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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I have a 03 Tahoe that I have been driving for about a year now, it has 113,000 miles on and it drives great. I have had no problems with at all, no hesitation in cranking or acceleration. Today however, I was driving on the highway at 70+ mph for about 40 miles, got to my destination fine, then went to crank it up with and the engine light came on and “reduced engine power” came up at the same time. This is the first time ever seeing the engine light or that message. I turned it off and back on and it was still there. I drove around a few blocks or so and was unable to go faster than 20mph or so. I was told by my mechanic that this was a safety feature on GM, so that you won’t do any further damage to the engine, and that he couldn’t tell me anything till he takes a look at it. So I parked it for a few minutes trying to figure out what to do sense I’m 40 miles away from home, I then cranked it back up, the engine light still on but was not showing the reduced engine power anymore, so I thought I would drive it to the nearest Advanced Auto Parts so the could check the light. Turning the engine off while I went inside and came out, he hooked it up to his machine where it read “Speed Sensor” and or “Throttle Control Sensor” I believe that’s what the name is, lol. So anyway he turned it off and on a few times then the engine light stayed off, he also said that it was showing something was wrong with the rear end, and that it had been doing it for a while off and on. He couldn’t tell me what was wrong with the rear end but it needed to be looked at. He also said that I was safe to drive back home on the interstate at high speed. The truck did perfect the whole way home. I don’t know what to do. Do I replace this Speed Sensor and Throttle Body? Was it a fluke mishap? From everything I’m reading on the Internet people are experiencing the same thing, replacing the part, and it still does the same thing. Please help, I have four kids that drive around daily in this vehicle, I don’t want to waste a lot of money and it not fix the problem, but at the same time I don’t want this to happen again while in driving down the interstate with my children inside. What do I do? What do I need to replace.
Concerned Tahoe Owner
My guess would be that there is excessive carbon build up on the throttle plate and bore. After the battery was disconnected the PCM learned memory was erased. The PCM commanded the throttle plate to a more closed position that it should be in if it were new. The throttle plate is now stuck in the carbon build up. A good cleaning of the throttle plate and bore using an approved throttle body cleaner on a rag (do not spray the inside of the throttle body with the cleaner) and the problem may correct itself. By the way there is also a good chance that the air in the heater-a/c system will now only blow out of the defrost.
I have a 2003 chevy trailblazer. i was installing a amp in it for my subwoofers and i unhooked the battery terminal so i could connect the postive wire. after connecting the terminal back i went to start the vehicle and my service light is on and the reduced power light is on. what has happened
Reduced engine power on 05 Tahoe – after replacing the throttle body harness and wiring, the throttle body and the TAC module I was still having the issue and multiple codes still came up. I had a battery that was under a year old and was not having any issue with it. I came out one morning and it was dead. I jumped it and it was fine but was dead the next morning. I then took the battery back and got a new one. I have been driving my 05 tahoe for a month now with NO reduced engine power…knock on wood it is hopefully fixed. Only time will tell. Thanks for the help.
I believe the recalibration that I mentioned was related to the HVAC actuators. If your idle is high after replacing or cleaning a throttle body the PCM memory needs to be cleared, to correct the condition. The simplest way to do that is disconnect the battery for a minute. The problem is that disconnecting the battery starts the recalibration process for the HVAC actuators. To avoid an actuator recalibration, that could leave you with a malfunction in your HVAC system. Of course if there is a malfunction that the recalibration will find, it will show up eventually. However to avoid it happening right now, I would recommend removing the “PCM B” fuse in the underhood fuse box. This will clear the PCM learned memory without affecting other systems.