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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 Signal - Rear Fascia B3121 02 B3121 05 B3121 05 -
Keyless Entry Antenna Low Reference - Rear Fascia - B3121 05 - -


Circuit/System Description

The rear fascia antenna is located in the rear fascia assembly and is used to establish low frequency communications with the keyless entry transmitter. As a vehicle with locked doors is approached with a keyless entry transmitter and the exterior rear closure touch pad is pressed, the keyless entry control module communicates with the rear fascia keyless entry antenna.

Conditions for Running the DTC


• The rear closure touch pad is pressed.

• The scan tool activates a device control function to simulate the above action.


Conditions for Setting the DTC

B3121 02

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

B3121 05

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

Action Taken When the DTC Sets

Rear closure will not open when rear closure touch 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 (without ATH) Keyless Entry System Description and Operation (with 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 Verification

Verify DTC B3122, B3123, or B3124 is not set.

Circuit/System Testing


1. Ignition OFF, disconnect the harness connector at the T10G rear fascia keyless entry antenna.

2. Ignition ON, test for less than 1 V between the signal circuit terminal 1 and ground.

3. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K84 keyless entry control module.

4.
Note

When using the MIN MAX function, auto-range may not function on the DMM. To ensure accurate test results, turn off auto-range and manually set the DMM range to 000.0 V.


Ignition OFF, install a DMM between the signal circuit terminal 1 and ground. Set the DMM to capture DC voltage using the MIN MAX function.

5. Activate the antenna by pressing the rear closure touch pad. Verify the MAX voltage captured by the DMM is greater than 1.0 V.

6. If less than the specified range, 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.

7. Test for less than 1 V between the low reference circuit terminal 2 and ground.

8. If greater than the specified range, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the K84 keyless entry control module.

9.
Note

When using the MIN MAX function, auto-range may not function on the DMM. To ensure accurate test results, turn off auto-range and manually set the DMM range to 000.0 V.


Install a DMM between the signal circuit terminal 1 and the low reference circuit terminal 2. Set the DMM to capture DC voltage using the MIN MAX function.

10. Activate the antenna by pressing the rear closure touch pad. Verify the MAX voltage captured by the DMM is greater than 1.0 V.

11. If less than the specified range, test the low reference circuit for an open circuit/high resistance. If the circuit tests normal, replace the K84 keyless entry control module.

12. If the test results for all circuits are normal, replace the T10G keyless entry antenna in the rear fascia. Verify that DTC B3121 is not set.

13. If the DTC is set, replace the K84 keyless entry control module.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Ignition Lock Key Transmitter Antenna Replacement - Rear Bumper Fascia

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