How can you reset reverse sensing system on a 2003 Lincoln navigator keeps saying check back up assistance?

There's no single "reset" button for the backup assist system on a 2003 Lincoln Navigator. The "Check Backup Assistance" message usually indicates a problem within the system itself, not just a software glitch. Troubleshooting steps are necessary to identify and fix the underlying issue. Here's a breakdown of how to approach this:

1. Check the Obvious:

* Sensors: Carefully examine all four backup sensors (usually located in the rear bumper). Look for any visible damage, dirt, ice, or obstructions blocking them. Clean them with a damp cloth if needed. Sometimes a small amount of mud or snow can cause this error.

* Wiring: Inspect the wiring harness connecting the sensors to the control module. Look for any loose connections, frayed wires, or signs of damage. This is more difficult and requires some mechanical skill.

* Rear Bumper: Ensure the bumper hasn't been bumped or shifted, potentially misaligning the sensors.

2. More Advanced Troubleshooting:

* Fuse: Check the fuse for the backup sensors in the fuse box (consult your owner's manual for the correct fuse location and rating). Replace it if it's blown.

* Control Module: The backup assist system has a control module that processes the sensor signals. This is the most likely culprit if the sensors and wiring look okay. Unfortunately, diagnosing a faulty module typically requires a scan tool that can read diagnostic trouble codes (DTCs) from the vehicle's computer. A mechanic or auto parts store with diagnostic equipment can do this.

* Wiring Harness Issues: A break or short in the wiring harness between the sensors and the control module could also be at fault. Finding this requires careful tracing of the wires.

3. Dealer/Mechanic Visit:

If you've checked the above and the message persists, it's time to seek professional help. A mechanic with a scan tool can:

* Read DTCs: Obtain diagnostic trouble codes which pinpoint the problem.

* Test Components: Systematically test the sensors, wiring, and control module to identify the faulty part.

* Repair or Replace: Repair or replace the malfunctioning component.

Important Note: The 2003 Lincoln Navigator's backup assist system is not sophisticated like modern systems. There's no simple "reset" procedure. Addressing the underlying electrical or sensor issue is key. A simple cleaning of sensors is often the solution, but more complex repairs may be required.