Bypass Essentials 556UW Universal Bypass

Allows remote start in vehicles equipped with a transponder or radio-frequency based immobilizer

Save up to $100
on security accessories
with a select security system with a select security system
  • Bypass Essentials 556UW Universal Bypass


Crutchfield OMC logo
We don't check this item for fit or compatibility.

Our take on the Bypass Essentials 556UW Universal Bypass

by Gabrielle Thorndyke

Bypass Essentials modules work with your vehicle's anti-theft system to incorporate the convenience, security and luxury features of your Python alarm system.

Universal bypass modules work with any vehicle using an "immobilizer" key system, allowing you to remote start your car without disrupting factory-installed anti-theft features.

Use the 556U universal bypass in vehicles equipped with a transponder or RF-based immobilizer, such as those found in many late-model GM vehicles. The compact module is tunable for European or domestic vehicles and features tamper-resistant circuitry.

Important Note: One of your car's transponder keys will be permanently installed in the 556U module. You can buy an extra key through your dealer and have it programmed to work with your car's immobilizer. Ask your dealer if keys can be programmed individually — some vehicle manufacturers require that all keys be reprogrammed at one time.

See more info on this item


  • universal bypass for Python alarm systems
  • compatible with any factory RF immobilizer or transponder system, including GM Passkey3
  • temporarily overrides the factory immobilizer
  • maintains integrity of factory anti-theft system
  • kit can be tuned for use with European or domestic vehicles
  • supplied harnesses splice into factory wiring
  • requires permanent key mount (into compact module)
  • warranty: 1 year
  • Our 60-day money-back guarantee

Important: If you know how to use a multimeter and have experience working with your vehicle's electrical system, you should be able to install this car security equipment. If you're unfamiliar with installing car security equipment, please speak to an Advisor before attempting this installation. Note: Before purchasing, please call us at 1-888-955-6000 to confirm that this product works with your vehicle.

Hands-on research from the Crutchfield Labs (what are the Labs?)

Product Research
What's in the box?

Download owner's manual

  • Universal remote start interface module
  • 6-Pin harness
  • 3-Pin harness
  • Instructions sheet

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team — they open the box, verify contents, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.


Overview: The 556UW immobilizer interface module is used when installing remote start products (sold separately) in select vehicles equipped with an RF (Radio Frequency) based immobilizer system. This type of system uses a small chip imbedded in the ignition key, called a transponder, to transmit a very low powered RF signal. This signal is picked up through an antenna (or coil) around the ignition switch which is then sent to the immobilizer's transceiver. Once the correct signal is received, the immobilizer will enable the ignition and/or fuel systems. If an attempt is made to start the vehicle and the transceiver does not receive a valid code, the ignition and sometimes the fuel systems are disabled. The immobilizer system will then render the remote start useless. The 556U bypasses the immobilizer system only while the remote start is in use, maintaining the factory system's integrity. When the remote start system is not in use the factory immobilizer remains fully functional.

Installation: The 556UW requires an active key from your vehicle to be installed inside the immobilizer interface module. The 556UW is then mounted underneath your vehicle's steering column. The 556UW immobilizer interface module features the following connections.

  • 6-Pin Harness: Power/Ground/Input Harness
    • Red (+)12 Volt Input: connect this wire to a fused source of constant 12 volt
    • Blue (-) Status Input: connect this wire to the remote start negative (-) status output
    • Pink (+) Ignition Input: connect this wire to the vehicle's true ignition output
    • Black (-) Chassis Ground: connect this wire to the vehicle's chassis ground
    • Violet (+) Key-Sense Input: connect this wire to the vehicle's positive key-sense output wire
    • Green (-) Key-Sense Input: connect this wire to the vehicle's negative key-sense output wire
  • 3-Pin Harness: Antenna harness
    • Black and Black/Red Wires: both of these are antenna ring wires
    • Black and White Wire: closed input wire
Review this product
Great Gear Giveaway rewards card

Submit a review and then enter to win a $500 rewards card

Bypass Essentials 556UW Universal Bypass Reviews

Average Customer Review:

1 people say:

Review this product:

Thanks for taking the time to share your experiences about this product. Please be sure to focus your comments on the product itself. Read our Review Guidelines for more information.

Your email won't be visible. Please use the email address that is associated with your order.
(e.g., JohnD) Your review will be signed using the display name and location
(e.g., Charlottesville, VA)

Click on a star to rate the overall product on a scale of 1-5
1500 characters left
Attach a YouTube Review
Crutchfield Video Review Guidelines
  • Only submit videos that you made or are authorized to use.
  • Do not submit videos that contain music, video or visuals that are copyrighted and belong to someone else.
  • Please see our Review Guidelines for more information.
500 characters left
500 characters left
Filter by rating:
3 out of 5


Written By Greg, Dover, NH on Tuesday, December 31, 2013
Crutchfield Customer Review (What's this?)
This product did not fit my mercedes key.
Was this review helpful?    Yes | No

For a more in-depth review and enhanced detailed information on the Bypass Essentials 556UW Universal Bypass, please visit the Crutchfield website product page (/ISEO-rccbcspd/p_607556UW/Bypass-Essentials-556UW-Universal-Bypass.html ).