Technician A says that piggybacks can modify the signal coming from the PCM to an actuator. Technician B says that a piggyback controller can be tuned to change the PCM's control strategy. Which technician is correct?

Technician A says that piggybacks can modify the signal coming from the PCM to an actuator. Technician B says that a piggyback controller can be tuned to change the PCM's control strategy. Which technician is correct?

• A. Both
• B. Technician B
• C. Technician A
• D. Neither

Answer: (C)

Piggyback controllers sit between the PCM and the engine’s actuators (or between sensors and the PCM) and modify the signals as they pass through. They don’t replace or rewrite the PCM’s software; instead they intercept the PCM’s outputs or sensor inputs and change them before they reach the actuator. This is why they can alter how the actuator responds without changing the PCM’s internal control logic. For example, a piggyback might scale a fuel injector signal or invert a sensor signal so the actuator behaves differently, while the PCM continues to run its own programmed control strategy. If you needed to change the PCM’s actual control algorithm, you’d look to reflash or replace the ECU, not a piggyback module. So the statement that a piggyback can modify the signal from the PCM to an actuator is correct, while the idea that it can tune to change the PCM’s control strategy is not the typical function of a piggyback.

Piggyback controllers sit between the PCM and the engine’s actuators (or between sensors and the PCM) and modify the signals as they pass through. They don’t replace or rewrite the PCM’s software; instead they intercept the PCM’s outputs or sensor inputs and change them before they reach the actuator. This is why they can alter how the actuator responds without changing the PCM’s internal control logic.

For example, a piggyback might scale a fuel injector signal or invert a sensor signal so the actuator behaves differently, while the PCM continues to run its own programmed control strategy. If you needed to change the PCM’s actual control algorithm, you’d look to reflash or replace the ECU, not a piggyback module. So the statement that a piggyback can modify the signal from the PCM to an actuator is correct, while the idea that it can tune to change the PCM’s control strategy is not the typical function of a piggyback.