B3124 on 2011-2016 Chevrolet Cruze: Keyless Entry Antenna Fault Causes and Fixes

What's Unique About the 2011-2016 Chevrolet CRUZE

For the first-generation Cruze, this issue is so common that General Motors issued a Technical Service Bulletin (TSB PIC6149A). 🎬 Watch: How the Remote Keyless Entry system should normally operate. The primary culprits identified by GM are not necessarily part failures, but rather simple physical issues: objects in the trunk blocking the signal or the antenna being installed upside down from the factory or during a previous repair. This makes the diagnostic process unique, as the first step is always a physical inspection of the trunk's contents rather than an immediate electrical diagnosis. The antenna is located on the rear compartment floor, near the seat back and centered.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Generation note: The 2011-2016 year range primarily covers the first-generation Chevrolet Cruze. However, the 2016 model year was an overlap, with both the first-gen "Cruze Limited" and the new second-generation sedan being sold. The cited TSBs specifically mention the 2012-2015 Cruze and 2016 Cruze Limited, confirming this is a well-documented issue for the first generation.

Symptoms You May Notice

• "Service Keyless Start" message on the Driver Information Center (DIC).
• "Service Keyless Entry" message on the DIC.
• Inability to open the trunk using the keyless touch pad on the trunk lid.
• Difficulty starting the vehicle if the key fob is located in the trunk area, as the vehicle may not detect the key.
• Keyless entry buttons on the door handles may not function correctly.
• The car may not start with the push-button ignition, requiring the key fob to be placed in the center console transmitter pocket as an emergency measure.

Most Likely Causes

1. Objects Blocking Trunk Antenna 🔴 High Probability The antenna is located in the trunk, making it susceptible to signal interference from large metal objects like toolboxes, luggage with metal frames, or other equipment. This is the leading cause cited in GM's TSB #PIC6149A. One owner on a forum for a related Buick model found a magnet lying on top of the antenna was the cause.
   How to confirm: Visually inspect the trunk for any large items, especially metallic ones, that could be obstructing the signal. Remove the items, clear the code, and see if the issue resolves.
   Typical fix: Remove obstructing objects from the trunk.
   Est. part cost: $0
2. Antenna Installed Incorrectly 🟡 Medium Probability TSB #PIC6149A notes that the rear compartment antenna can be installed upside down, which impairs its function. This could happen at the factory or during a previous repair. The TSB includes images showing the correct vs. incorrect orientation.
   How to confirm: Locate the antenna in the trunk area (often behind the trunk liner near the rear seatback or on the parcel shelf) and compare its installation to diagrams in the service manual or the TSB.
   Typical fix: Correctly orient and reinstall the antenna.
   Est. part cost: $0
3. Wiring or Connector Issue ⚪ Low Probability The wiring harness leading to the antenna can become damaged, or the connector can become loose or corroded. A video of a similar GM vehicle (2017 Tahoe) showed the connector for the rear antenna simply coming unplugged due to its location under the carpet where it could be kicked or disturbed. The connector can be checked for a secure fit.
   How to confirm: Inspect the wiring harness for visible damage. Disconnect the connector, check for corrosion on the pins, and ensure it is securely reconnected. A multimeter can be used to check for an open or short in the circuit.
   Typical fix: Repair the damaged wire or clean/re-seat the connector.
   Est. part cost: $5-$20
4. Faulty Rear Compartment Antenna ⚪ Low Probability Like any electronic component, the antenna can fail over time due to internal faults or physical damage. It is a simple, non-powered component that is part of a larger circuit controlled by the Keyless Entry Control Module.
   How to confirm: If the trunk is clear, the antenna is installed correctly, and the wiring/connector are good, the antenna itself is the next suspect. A technician can test the circuit's continuity and resistance. If the wiring is good, the antenna is likely faulty.
   Typical fix: Replace the rear compartment keyless entry antenna.
   Est. part cost: $25-$50

Rare But Worth Checking

• Body Control Module (BCM) or Keyless Entry Control Module (K84) Fault: This is very rare. The BCM and the dedicated Keyless Entry Control Module (K84) are the computers that control the system. All other possibilities, especially the antenna and its wiring, should be exhausted before considering module replacement, as it is expensive and requires programming.
• Blown PEPS Fuse: While less likely to isolate to a single antenna and trigger B3124, a problem with the Passive Entry Passive Start (PEPS) fuse can cause general keyless system failure. It's a quick check to rule out. A video guide shows this fuse is located in the under-hood fuse block.

Diagnosis Steps

1. Read the code with an OBD-II scanner to confirm B3124 is present. Note the full description, such as 'Short to Ground' or 'High Voltage/Open'.
2. Check the Driver Information Center for messages like "Service Keyless Start".
3. Thoroughly inspect the trunk and remove any large objects, especially anything metallic or electronic (toolboxes, luggage, laptops), that could block the antenna signal.
4. Clear the trouble code using the scanner and test the keyless entry functions (trunk release, door locks, push-button start) to see if the problem is resolved.
5. If the code returns, locate the rear compartment antenna. It is located on the rear compartment floor, near the seat back, and centered under the trunk liner/carpet.
6. Visually inspect the antenna to ensure it is installed correctly (not upside down) as per TSB PIC6149A.
7. Inspect the antenna's electrical connector. Ensure it is securely plugged in. On some GM vehicles, these connectors can become dislodged. Check for any signs of corrosion or damage to the wiring harness.
8. If a multimeter is available, test the antenna circuit for continuity, shorts to ground, or shorts to power, following the service manual procedure for DTC B3124.
9. If the wiring and connections are good and the antenna is oriented correctly, the antenna itself is the most likely failed component and should be replaced.

Parts You'll Likely Need

• Keyless Entry Rear Compartment Antenna (OEM #13502554) — If clearing obstructions and checking wiring doesn't solve the problem, the antenna itself has likely failed. This part is responsible for receiving the key fob's signal in the trunk area. This part number is widely used across many GM vehicles.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $28-$40
  Aftermarket price range: $25-$40

Technical Service Bulletins (TSBs) & Recalls

• PIC6149A: "Diagnostic Tip – Service Keyless Start Message" - Advises checking for objects blocking the rear antenna or for incorrect installation of the antenna. This TSB covers the 2012-2015 Cruze and 2016 Cruze Limited.
• PIC6149: The predecessor to PIC6149A, with similar information.

Platform-Specific Known Issues

• A known issue documented in GM Technical Service Bulletin #PIC6149A involves objects in the trunk blocking the antenna signal, causing intermittent B3124 codes and "Service Keyless Start" messages.
• The same TSB also notes that the rear compartment antenna may be installed upside down from the factory or during a prior repair, requiring inspection and correction. The TSB provides images for comparison.
• The antenna is specifically located on the floor of the rear compartment, near the seat back and centered, making it prone to being covered by cargo.

Mechanic-Grade Diagnostic Values

• Voltage between antenna signal circuit and ground (at K84 module connector) — expected: Less than 1 V. Failure: 1 V or greater indicates a short to voltage in the circuit.
• Resistance of the antenna low reference circuit end-to-end — expected: Less than 2 ohms. Failure: 2 ohms or greater indicates an open or high resistance in the circuit.

Hidden / Shadow Codes Worth Checking

• B3124 02: Indicates the Keyless Entry Control Module has detected a short to ground on the rear compartment keyless entry antenna signal circuit. (see via A professional scan tool capable of reading GM-specific symptom bytes, like a GDS2 or high-end aftermarket scanner.)
• B3124 05: Indicates the Keyless Entry Control Module has detected a short to voltage (B+) or an open circuit on the rear compartment keyless entry antenna signal circuit. (see via A professional scan tool capable of reading GM-specific symptom bytes, like a GDS2 or high-end aftermarket scanner.)

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Module Diagnostics > K84 Keyless Entry Control Module > Data Display — To view the status and any specific fault data related to all keyless entry antennas simultaneously. This helps confirm if the fault is isolated to Antenna 6 (B3124) or if other antennas are also malfunctioning.
• GDS2 (GM Global Diagnostic System 2): Clear DTCs — After performing a physical repair (like removing an obstruction or reconnecting the antenna), this command is used to clear the code from the module's memory. The system performs a self-check on the next key cycle to verify the fix.

Wiring & Ground Locations

• K84 Keyless Entry Control Module — In the trunk, located near the spare tire well area. You may need to remove the trunk floor covering/liner to access it.. This is the computer that directly communicates with and monitors the rear compartment antenna (Antenna 6). All diagnostic circuit tests for the antenna originate at the connector for this module.
• T10E Rear Compartment Keyless Entry Antenna — On the rear compartment floor, near the seat back, and centered under the trunk liner.. This is the specific component ('Antenna 6') that code B3124 refers to. Its location makes it prone to being blocked by cargo or having its connector dislodged.
• Underhood Fuse Block (X50A) — In the engine bay, on the driver's side.. This fuse block contains the PEPS (Passive Entry Passive Start) fuse, typically F27 in the instrument panel fuse block which is powered by the underhood block. A failure of this fuse would likely cause more codes but is a quick check for general keyless system issues.

Real Owner Repair Stories

• YouTube video on a 2017 Tahoe (similar GM system) (2017 Chevrolet Tahoe) — Dashboard message and code B3124 05 (short to voltage/open).
  ❌ Tried (didn't work) The video directly addresses the common failure, implying other diagnostics were unnecessary.
  ✅ What actually fixed it The connector for the rear antenna, located under the carpet behind the second-row seats, had come unplugged. The technician lifted the carpet, securely reconnected the plug, and the code cleared itself upon the next vehicle start cycle.
• YouTube video on a GM Tracker (similar GM system) (GM Tracker (year not specified)) — "Failure in the keyless start system" message on the dash and DTC B3124 (open circuit or short to battery). Keyless entry buttons on door handles did not work.
  ❌ Tried (didn't work) Checked for aftermarket trackers or wiring modifications.
  ✅ What actually fixed it The rear antenna, located near the spare tire next to the keyless entry module, was found disconnected. The connector's locking tab was broken, causing it to come loose. Reconnecting it solved the problem instantly, restoring keyless entry and clearing the message.

OEM Part Supersession History

• 13502554 → 13502554 (current) — This part number has remained stable and is used across a wide range of GM vehicles, including Buick, Cadillac, and Chevrolet models from approximately 2010-2020.

Model Year Variations Within This Range

• 2016: In 2016, GM sold two different cars named 'Cruze'. The 'Cruze Limited' was a continuation of the first-generation (2011-2015) model, and all information related to TSB PIC6149A and code B3124 applies to it. The 'all-new' 2016 Cruze was the first year of the second generation, featuring a completely different body, engine, and updated electronics. While it has a similar keyless entry system, part locations and specifics may differ.