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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As far as I know GM only sells the pedal assembly and that is what I recommend. As far as testing goes,there are multiple methods and it may take several to locate the issue. It involves watching scan data, voltmeter or oscilloscope readings while depressing the gas pedal and possibly wiggling the harnesses. This testing may have to be applied to any one or all nine wires involved. To save expense on the instrument cluster, there are several companies that you can send it to to have the stepper motors for the gauges changed. Usually in the $200 +/- range and you can avoid programming costs. Done at the dealership it is in the $500-$550 range. Yous could be slightly higher since the 2500HD should have seven gauges instead of the normal six.
I strongly recommend testing to be sure of the problem and it’s solution. If you are looking for a silver bullet repair, the best I could suggest is genuine GM // AC Delco parts.
Ok how do I get that tested? And do I replace just the accelerator sensor or the whole pedal assembly? This is the last I’m trying then will bring to Chevy. Also I’m gonna replace the instrument cluster. From Jamie and thanks for all the help really apreciated
The P1125 code will be the root cause of your issue. The code is for a problem with the signals between the APP sensors and the TAC module. Possible causes are a faulty gas pedal assembly ( I know you stated earlier that you replaced it. Problems have been developing with some new after market gas pedal assemblies), a faulty TAC module or faulty wiring connections between the two.
Ok sparky so do I replace gas pedal sensor again or whole gas pedal assembly?
Sparky, I located the ground on the back of the engine and indeed it was holding on by one strand. I extended it and ran it to the accesible ground on the other side of the engine and drove down the bumpiest road in town and not a single glitch!! Thank You very much for your input. I beleive the problem is resolved finally!!
Hanns Mercer, Sheridan WY.
Hi Jamie,
I understand your problem is bothering you a great deal but from my side it is hard to get a grip on diagnosing “DTC something”. Sadly from experience I can however guess it was a code P0449.
Sparky. Jamie.. Ok when it is not in reduced engine mode there are no codes, wen it’s in the mode I get… P0300 random cylinder misfires. P0455 evac system large leak.. P1125 app system enhanced.. Thanks for your time.