P1516 is a very common trouble code. It is a GM ONLY code, which means that it has the same meaning only for GM vehicles, such as the Pontiac G8. A P1516 for a Hyundai, for example, means something totally different.
Trouble code P1516 lets you know that the Throttle Actuator Control (TAC) Module has a performance issue related to it’s position. It can cause the “Reduced Engine Power” warning to display. P1516 needs dealt with as soon as possible.
There are two circuits that handle the TAC data, Motor Control 1 and Motor Control 2. These circuits help determine and execute the throttle response based on how far you have pushed the gas. This process is in place to help ease wear and tear and increase fuel mileage by taking direct control of the throttle out of the driver’s hand (or foot).
Here are the most common symptoms associated with P1516 in the Pontiac G8:
- Service Engine Soon– The ECM will throw the service engine soon light (probably why you’re here).
- Reduced Engine Power– The vehicle will run with a much narrower power band to avoid over acceleration. This is a failsafe mechanism that keeps the G8 from “running away” on you.
G8 P1516 Causes
P1516 is going to be caused by the ECM detecting that the predicted and actual throttle position are not within the proper range. The ECM will often reduce the engine power for safety. Clearing P1516 will restore engine power if it is the only trouble code related to the problem that you currently have.
Pontiac G8 P1516 Diagnosis
Almost all of the potential causes of the P1516 trouble code are going to have to do with the TAC Module. They are presented (somewhat) in order from most to least likely for troubleshooting purposes:
- TAC Module failure– The most common cause of the P1516 in the Pontiac G8 is when the Throttle Actuator Position Module itself fails.
- TAC Module wiring issues– Often, the wiring around the TAC Module will become loose or damaged. It only takes a few moments to inspect the TAC Module, and can save you a lot of time and money. This video is a great resource for chasing down short circuit issues: How to Diagnose and Find a Short (YouTube).
- Throttle Blade Issues– If the throttle blade is not returning to its resting place quickly enough when you let off of the throttle, it’ll throw P1516. A good indication that this is a problem is if the engine feels like it’s going to die for just a second after letting off of the gas, especially coming down from higher speed or acceleration.
- Water damage to the TAC Module– Although this one is less likely than a wiring issue, water damage can affect the TAC module as well.
When the TAC module goes bad in the Pontiac G8, it’ll often throw the P1516 code. Getting it dealt with as soon as possible has to be a high priority. Good luck fixing your G8, and please leave a comment it you have any questions or anything you’d like to add. Good luck!