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DTC B3121

DTC B3121

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.


DTC Descriptors

DTC B3121 02

Keyless Entry Antenna 3 Short to Ground

DTC B3121 05

Keyless Entry Antenna 3 High Voltage/Open

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Keyless Entry Antenna - Rear Compartment Signal

B3121 02

B3121 05

B3121 05

-

Keyless Entry Antenna - Rear Compartment Low Reference

-

B3121 05

-

-



Circuit/System Description

The rear compartment keyless entry antenna is used to establish low frequency communications with the keyless entry transmitter. As a vehicle with a closed rear compartment lid is approached with a keyless entry transmitter, known as an user identification device, and the rear compartment lid release switch is pressed, the keyless entry antenna transmitter broadcasts a challenge to the transmitter in an approximate 1 m (3.28 ft) range. If the response from the transmitter via radio frequency is valid, the latched rear compartment will be passively unlocked/unlatched, allowing the rear compartment area to be opened.

Conditions for Running the DTC

The handle or touch pad used to open the rear closure is activated.

Conditions for Setting the DTC

B3121 02

The keyless entry control module detects a short to ground on the rear compartment keyless entry antenna circuit.

B3121 05

The keyless entry control module detects a short to B+ or an open on the rear compartment keyless entry antenna circuit.

Action Taken When the DTC Sets

Rear closure will not open when rear closure touched pad is pressed.

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 40 malfunction-free ignition cycles.


Reference Information

Schematic Reference

Remote Function Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Keyless Entry System Description and Operation (With ATH) Keyless Entry System Description and Operation (Without ATH)

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

Note

Verify that the pins are correct for all of the antennas. Make sure to fix any problems with the interior antennas first, before proceeding to the following diagnostics below regarding the exterior antennas. If any of the interior antenna DTCs B3122, B3123, B3124 is set, the diagnostic procedures on the exterior antennas will not work.



1. Ignition OFF, disconnect the harness connector at the T10E Keyless Entry Antenna - Rear Compartment.

2. Ignition ON, verify a test lamp does not illuminate between the signal circuit terminal 1 and ground.

3. If the test lamp illuminates, test the signal circuit for a short to voltage. If the circuit tests normal replace the K84 Keyless Entry Control Module.

4. Verify a test lamp does not illuminate between the low reference circuit terminal 2 and ground.

5. If the test lamp illuminates, test the low reference circuit for a short to voltage. If the circuit tests normal replace the K84 Keyless Entry Control Module.

6. Connect a DMM, set to capture alternating voltage using the MIN MAX function, between the signal circuit terminal 1 and ground.

7.
Note

Use DC voltage because comparing to vehicle ground.


Activate the rear compartment antenna by manually pressing the rear closure touch pad. After pressing the MIN/MAX button looking for any voltage, verify the DMM captured a DC voltage signal.

8. If the DC voltage was not captured, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal replace the K84 Keyless Entry Control Module.

9. Connect a DMM, set to capture alternating voltage using the MIN MAX function, between the signal circuit terminal 1 and the low reference circuit terminal 2.

10. Activate the rear compartment antenna by manually pressing the rear closure touch pad. After pressing the MIN/MAX button looking for any voltage, verify the DMM captured a DC voltage signal.

11. If the DC voltage was not captured, test the low reference circuit for a short to ground or an open/high resistance. If the circuit tests normal replace the K84 Keyless Entry Control Module.

12. If all circuits test normal, replace the T10E Keyless Entry Antenna - Rear Compartment. Clear DTCs and then press the tailgate touch pad and check for any DTCs. If DTC B3121 returns, replace the K84 keyless entry control unit.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for keyless entry control module replacement, setup and programming