Volt

DTC B3121

The rear fascia aerial 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 aerial.

B3121 02

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

B3121 05

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

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

Schematic Reference

Remote Function Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Keyless Entry System Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Vehicle in Service Mode.
2. Verify that DTC B3122, B3123, or B3124 is not set.

⇒	If any of the DTCs are set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle .

⇓	If none of the DTCs are set

3. Refer to Circuit/System Testing.

1. Vehicle OFF, disconnect the harness connector at the T10G rear fascia keyless entry aerial, Vehicle in Service Mode.
2. Test for less than 1 V between the signal circuit terminal 1 and ground.

⇒	If 1 V or greater

2.1.	Vehicle OFF, disconnect the harness connector at the K84 keyless entry control module, Vehicle in Service Mode.

2.2.	Test for less than 1 V between the signal circuit and ground.

⇒	If 1 V or greater, repair the short to voltage on the circuit.

⇒	If less than 1 V, replace the K84 keyless entry control module.

⇓	If less than 1 V

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

3. Vehicle OFF, install a DMM between the signal circuit terminal 1 and ground. Set the DMM to capture DC voltage using the MIN MAX function.
4. Lock the vehicle doors using the keyless entry transmitter. Activate the aerial by pulling the driver exterior door handle. Activate the aerial by pressing the rear closure touch pad.
5. Verify the MAX voltage captured by the DMM is greater than 0.5 V.

⇒	If 0.5 V or less

5.1.	Vehicle OFF, disconnect the harness connector at the K84 keyless entry control module.

5.2.	Test for infinite resistance between the signal circuit and ground.

⇒	If less than infinite resistance, repair the short to ground on the circuit.

⇓	If infinite resistance

5.3.	Test for less than 2 Ω in the signal circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K84 keyless entry control module.

⇓	If greater than 0.5V

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

6. 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.
7. Lock the vehicle doors using the keyless entry transmitter. Activate the aerial by pressing the rear closure touch pad.
8. Verify the MAX voltage captured by the DMM is greater than 0.5 V.

⇒	If 0.5 V or less

8.1.	Vehicle OFF, disconnect the harness connector at the K84 keyless entry control module.

8.2.	Test for less than 2 Ω in the low reference circuit end to end.

⇒	If 2 Ω or greater, repair the open/high resistance in the circuit.

⇒	If less than 2 Ω, replace the K84 keyless entry control module.

⇓	If greater than 0.5V

9. Replace the T10G rear fascia keyless entry aerial.
10. Lock the vehicle doors using the keyless entry transmitter. Activate the aerial by pressing the rear closure touch pad.
11. Verify DTC B3121 is not set as current.

⇒	If DTC B3121 is set as current

Replace the K84 keyless entry control module.

⇓	If DTC B3121 is not set or is set as history

12. All OK.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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