Mod: Backup Parking Sensor

Installation Of A Backup Parking Sensor.

My 2016 Ford Transit cargo van arrived with a backup camera installed as a standard feature and during the short time, that I’ve driven the van, I learned to love it.

Needless to say, that a backup parking sensor with an audible signal is fairly redundant. But as it is so inexpensive and easy to install, I decided to add it as an extra feature. Another sensor will be added to the front at a later stage of the conversion.

This project is geared towards a 2016 Ford Transit, but the techniques and materials can be used in other van conversions, such as MB Sprinters and Ram ProMasters as well.

What You’ll Learn:

  • How to remove the rear bumper cover.
  • How to tap into the Trailer Tow Harness.
  • How to ground your electrical connection.
  • How to splice a wire.

What You’ll Use:

  • Torque wrench and 5/16” socket.
  • Wrench with T-25 CR-V torx socket.
  • Multitester.
  • Wirestripper/Crimper.
  • Puncher (to split the wire).
  • Heat gun.
  • Scissors (to cut sensor strip).
  • Wheel chocks (wedges).
  • Power cord extension.
  • Optional:
    • Utility knive.
    • Toolbox.

What You’ll Need:

  • Electromagnetic sensor kit.
  • Ring terminal #10 – 14-16 AWG.
  • Heat shrink.
  • Spade terminals.
  • 16 AWG wire.
  • Electrical tape.
  • Thin flexible wire wrap.
  • Cable ties.
  • Alcohol swabs/rubbing alcohol/Windex.
  • Paper towels.
  • Optional:
    • Grommets.
    • Flexible wire wrap holders.


This electromagnetic parking sensor only works with plastic bumpers; if your vehicle still has a metal bumper, you should investigate ultrasonic sensors.

This unit supplements the visual data of the backup camera with an audible signal, when an obstruction blocks the vehicle’s path. The entire unit consists of a small processing unit with leads to a small speaker, to the sensor strip and to an available 12V power source.

The only issue is accessing the reverse circuit of the cargo van. On older vehicles, the reverse signal originated at one of the backup lights; that’s discouraged with newer vehicles such as the Ford Transit. Instead, the backup signal should be tapped into at the trailer towing harness, but that depends on how your van is equipped. ProMaster and Sprinter owners should follow their manufacturers guidelines.

My Transit has a trailer tow socket at the end of the fuel tank harness (3. Trailer Tow Socket Jumper – 4. Fuel Tank Harness) and is located 3 to 4 feet (1 meter) from rear bumper along the drivers side body support member.

The entire project is relatively easy to accomplish, with only the wire splicing at the trailer harness as being somewhat tricky. I made a separate video on splicing wire, if you need it.

When you decide to go ahead with the installation, you can use my experiences as a guide.

Approximate Duration For This Project: 3-5 hours.


This unit only works when the vehicle is moving, yet has the advantage that it requires little or no maintenance or cleaning, is out-of-sight and no permanent holes have to be drilled into your bumper.

I paid $9.78 for the Electromagnetic Backup Sensor (Sensor Strip | Sensor Module | Speaker | Wiring).

The Project

Gather all the tools and materials before proceeding. Use wheel chocks to immobilize the vehicle.

The Bumper

  • Remove the screws along the top of the plastic bumper cover. I used a wrench with a Torx T25 socket.
  • At each bottom end of the bumper, sits a ‘two-way’ plastic plug. Pull out the center and then the entire plug.
  • In between the two outside plugs are several ordinary plastic plugs. Pull them out cautiously and you can use them again.
  • Now you can remove the bumper cover.
  • Clean the inside area of the bumper, between both reflectors, with alcohol or plain Windex. Cut the sensor strip to size and affix it between the reflectors, with the spade connector on the driver’s side.
    These electromagnetic sensors have to be installed at approx. a 20 inch height (50 cm), which is the height of the bumper.
  • Attach the short extension wire and create a permanent connection with a piece of heat shrink. Extend it past the reflector and fasten it with a cable tie. Guide around the bumper to the van’s body frame.
  • Reinstall the bumper cover and reinsert the bottom plugs; continue with fastening the Torx screws at the top of the bumper.
  • We continue with the wiring under the van.

The Wiring

  • The one foot long extension wire is the disconnection point, whenever the bumper cover is to be removed and sits behind the bumper, close to the hitch and covered in wire wrap.
  • The included wiring harness contains a speaker wire with speaker attached and a power wire, both attached to a Molex connector that fits into the sensor module.
  • I enclose the speaker wire in wire wrap and push the end with the Molex connector down the rear door column/side wall into the frame’s cross beam.
  • Open the two compartments at the end of the cross beam, under the rear door column, by removing the two rubber covers.
  • Pull the wires out of the larger compartment and guide them back towards the smaller compartment.
  • You can place the sensor module in either compartment, where it is well protected against a harsh environment.
  • After connecting the wires to the module, wrap the power wires and guide them further through the cross beam to the next exit hole, through the rubber grommet to the trailer tow harness.
  • Insert the wires into the Trailer Tow Harness and tape the wraps together with electrical tape.
  • Follow the harness to where it connects with the Fuel Tank Harness.
  • Disconnect the Trailer Tow socket from the Fuel Tank harness.
  • Loosen the ground eyelet from the frame with a 5/16 socket.
  • Attach a #10 eyelet connector to the sensor’s ground wire and finish with a heat shrink.
  • Add to the existing eyelet (never more than two!) and reattach to the frame.
  • Expose the wiring to the existing socket, by removing the wire wrap.
  • Identify the Trailer Reverse Lamps wire. It’s the #4 gray-brown (GY-BN) 16 AWG wire.
  • Cut to length the sensor power wire and strip it back about one inch.
  • Now the tricky part. Cut through the #4 wire jacket, but leave the wire intact. Watch the ‘How To Splice A Wire’ video for an example.
  • Separate the exposed wire with a puncher or other pointy object, like a pencil.
  • Insert the power wire and fasten both to each other.
  • Cover the connection with electrical tape.
  • Tuck all the wiring back into the Trailer Tow Harness wrap and reconnect the socket.
  • Test the rear sensor:
    • Vehicle engine must be OFF.
    • Parking brake engaged.
    • Turn ignition key ON.
    • Place transmission in reverse.
    • Start at 6 feet (2 meters) behind bumper and slowly approach the bumper.
    • At 15-25 inches (35-60 cm) you hear a fast beep; at 8-15 inches (20-35 cm) a continuous beep.

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This project takes some time, but can be achieved during a weekend. You need to know how to work safely with wiring, but most of that is very basic work. The only tricky part is the connection between the sensor power wire and the Trailer Reverse Lamps wire; with a little care and a steady hand, that worked out fine for me.

Before starting this project, you should read through the Ford Transit Body and Equipment Mounting Manual, which you can download from the resources page.

Ford Transit Technical Details

Your Transit model has three possible configurations:

  • Vehicle is equipped with the factory trailer tow feature.
  • Vehicle is not equipped with a trailer tow option but has trailer tow wiring body harness.
  • Vehicle has neither the trailer tow wiring, nor the trailer tow body harness. (Built before 01/28/15).

Vehicles with the heavy duty trailer tow provision will have a hitch and trailer lighting connector socket.

Vehicles with the Trailer Tow feature have the Trailer Tow backup circuit (CAT16) present in the 14406 fuel tank harness. Item 4 shows the 14406 fuel tank harness where this circuit is located.

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1. Trailer Tow Module – 2. Trailer Tow Module Jumper – 3. Trailer Tow Socket Jumper – 4. Fuel Tank Harness – 5. Main Harness.

Pin 4 (the Gray/Brown wire) can be used to access the reverse signal. A ground eyelet can stacked on the existing Trailer Tow Ground eyelet shown circled in RED (max. 2 connections). Ground screw MUST be torqued 12.0 ± 1.8 Nm.

Connector pin out:
4 – CAT16 (GY-BN) – 16 gauge – Trailer Reverse Lamps.

Reverse Signal for aftermarket equipment such as backup alarms may be obtained at Pin 4 on the Trailer Tow 14406 in-line connector. This circuit is fuse protected to 10 Amps.

Good Wiring Practices

  • General
    In general, the distance between retention points for wiring not contained in a rigid shield should be less than 12″ (30cm). A minimum 1″ (25 mm) clearance is recommended from all sharp edges. The Transit electrical system is a 12-Volt supply with a negative ground return.
  • Connector Practices
    Female terminals in the harness side connection and the male terminals in the component side.
  • Grounding
    Do not place more than 2 eyelet terminals under a single ground screw.
  • Reversing Lamps
    Reversing lamps are activated when transmission is in reverse.
    The load on the reversing lamps should not exceed a total of 54W.
    The reverse tail lamp circuits are unable to support any additional load. Equipment that requires a reverse signal should use the reverse trailer tow.
  • Reverse Signal
    For after-market equipment such as backup alarms, the reverse signal may be obtained at Pin 4, on the Trailer Tow 14406 in-line connector. This circuit is fuse protected to 10 amps.

This Project’s Other Videos:

Other projects of this Van Conversion:

I’m just a DIY’er with a lot of common sense, but with some of the projects, I use some tools and materials, that require you to really know, what you’re doing. Always read the manual and consult an expert if you’re in doubt.

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