B3121

DTC B3121

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.



DTC Descriptors
DTC B3121 02
- Keyless Entry Antenna 3 Performance Short to Ground

DTC B3121 05
- Keyless Entry Antenna 3 Performance Short to Battery or Open




Diagnostic Fault Information






Circuit/System Description

The rear compartment keyless entry antenna is used as a short range low frequency (LF) transmitter. As a vehicle with a closed rear compartment lid is approached with a key fob and the rear compartment lid release switch is pressed, the keyless entry antenna transmitter broadcasts a challenge to the key fob in an approximate 1 meter range. If the response from the key fob via radio frequency (RF) is valid, the latched rear compartment will be passively unlocked/unlatched, allowing the rear compartment area to be opened.


Conditions for Running the DTC

A transmitter validation is requested.


Conditions for Setting the DTC

An improper voltage level is seen on the keyless entry antenna - signal 3 circuit.


Action Taken When the DTC Sets

The rear compartment keyless entry antenna is ignored.


Conditions for Clearing the DTC

* A current DTC will clear when the conditions for setting the DTC are no longer present.
* A history DTC will clear after 50 malfunction free ignition cycles.



Reference Information
Schematic Reference

Remote Function Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Keyless Entry System Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the rear compartment keyless entry antenna.
2. Ignition ON, verify a test lamp does not illuminate between the signal circuit terminal A and ground.

• If the test lamp illuminates, test the signal circuit for a short to voltage. If the circuit tests normal, replace the RCDLR.

3. Install a DMM between the signal circuit terminal A and the low reference circuit terminal B. Set the DMM to capture AC voltage using the MIN MAX function.
4. Press the rear compartment lid release switch. Verify the DMM captured an AC voltage signal.

• If an AC voltage was not captured, test the signal circuit and the low reference circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the RCDLR.

5. If all circuits test normal, test or replace the rear compartment keyless entry antenna.



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Ignition Lock Key Transmitter Antenna Replacement - Rear Compartment (Ignition Lock Key Transmitter Antenna Replacement - Rear Compartment)
* Control Module References (Programming and Relearning) for RCDLR replacement, setup, and programming