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Chevrolet Silverado 1999-2006: Error Code P1516

The P1516 engine code refers to the drive-by-wire system on your Chevrolet Silverado 1500. When a component on the system fails, the truck is forced to drive in reduced engine power mode. Read this article to learn more about the DBW system, and how to fix this common problem.

By Neftali Medina - June 4, 2015

This article applies to the Chevrolet Silverado 1500 (1999-2006).

The drive-by-wire (DBW) system uses sensors to determine how much force is being used to depress the gas pedal so it can easily open and close the throttle body, thereby impacting how fast the truck is traveling. It has been incorporated in most vehicles produced past the later 1990's and has replaced the mechanical throttle cable system. Unfortunately, since its use on the early first generation Silverados, the drive-by-wire system has experienced several different problems, all of which cause the same issue – the reduced engine power (REP) mode and error code P1516. The drive-by-wire system uses an acceleration pedal sensor (APP), throttle position sensor (TPS), TAC module and ECU programming sequence. First, we'll begin with a breakdown of the DBW system.

Component Breakdown

Accelerator Pedal Sensor

The accelerator pedal sensor is located at the top of the pedal assembly. It connects to the dashboard harness and is responsible for sending signals to the truck's ECU, which then travels to the throttle body. Each signal either opens or closes the throttle body and allows air into the engine.

Figure 1. This accelerator pedal sensor sends a signal to the ECU so the throttle body can open.

Throttle Position Sensor

This sensor is responsible for receiving the signal from the ECU and operating the servo motor. The servo motor then either opens or closes the butterfly flap found inside the throttle body.

Figure 2. Throttle position sensor located on the throttle body.

TAC Module

The TAC module acts as a bridge in-between the signals that are sent to the ECU, TPS, and APP. It checks each frequency and makes sure all are responding to the same parameters. In the instance where one or more components fail, the TAC module will turn on the REP mode.

Figure 3. TAC module.

Common Questions

How do I know if my truck has a drive-by-wire system?

The easiest way to see whether or not your truck has a drive-by-wire system is to open the hood and inspect the throttle body. If there isn't a throttle cable present, then the vehicle utilizes a drive-by-wire system.

What does the P1516 code stand for?

The code stands for "Throttle Actuator Control Module Throttle Actuator Position Performance," which can seem like gibberish, but is referring to a discrepancy found in-between the signals that the APP sensor is sending to the TAC module and TPS sensor.

Common Issues

The TPS is damaged

The throttle position sensor is damaged and requires replacement, which means it is sending inaccurate readings to the ECU.

The ECU needs to be updated

General Motors released an ECU update in the late 2000's which fixed a discrepancy in the programming. The dealership will have to update the computer and, in some cases, replace the throttle position sensor or complete throttle body.

The TAC module is damaged

If the TAC module is damaged and no longer reading the correct frequencies between the accelerator pedal and throttle position sensor, then the unit will have to be completely replaced.

Technical Service Bulletins (TSBs)

  • 2006-09-01 A/T – Throttle actuator control (TAC) module codes, mil/ses dtc's p2108, p1516, u0107, reduced engine power.

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