GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 DTC 🢒 DTC B3120

Circuit Description

The keyless entry antenna - right is located in the right hand door pull handle and is used as a short range low frequency (LF) antenna. As a vehicle with locked doors is approached with a valid keyless entry transmitter, and the exterior door handle is pulled, the keyless entry antenna broadcasts a challenge to the transmitter in approximately a 1 meter range. If the response from the transmitter via radio frequency (RF) is valid, then the locked door will be passively unlocked/unlatched and allow the door to be opened.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B3120 Keyless Entry Antenna 2 Performance

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description in Vehicle DTC Information.

DTC Symptom

DTC Symptom Descriptor

02

Short to Ground

05

Short to Battery or Open

Conditions for Setting the DTC

The remote control door lock receiver (RCDLR) will set this DTC during antenna authentication if the keyless entry antenna - right is open, shorted to battery positive voltage, or shorted to ground. The RCDLR can only set a DTC when the vehicle system voltage is between 9-16 volts.

Action Taken When the DTC Sets

The RCDLR will set and store DTC B3120 Keyless Entry Antenna 2 Performance.

Conditions for Clearing the DTC
    • The RCDLR no longer detects an open, short to power, or short to ground on the antenna circuit.
    • The use of a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Verifies that DTC B3120 is a current DTC.

    2.

  2. Verifies that the passenger door handle is operating properly. A valid input from the passenger door handle is required by the RCDLR to authenticate the antenna.

    3.

  3. Testing for power and ground to the keyless entry antenna.

Step

Action

Yes

No

Schematic Reference: Keyless Entry Schematics

Connector End View Reference: Keyless Entry Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Important: To achieve service by pass mode, key ON, engine OFF, a programmed transmitter must be detected within the passenger compartment of the vehicle.

  1. Install a scan tool.
  2. Push and hold the ACC button for 5 seconds to achieve the service bypass mode, with the engine OFF.
  3. Select display DTCs function on the scan tool in the remote control door lock receiver (RCDLR) menu.

Does the scan tool display DTC B3120 as a current DTC?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3

  1. With the scan tool, observe the passenger door handle parameter in the passenger door module (PDM) data list.
  2. Operate the passenger exterior door handle.

Does the passenger door handle state display INACTIVE?

Go to Power Door Latch Inoperative - Passenger Door

Go to Step 4

4

Important: 

   • The voltage signal sent by the RCDLR to the passive antenna is a AC voltage signal. The DMM must be set on AC voltage setting to record the voltage pulse to the passive antenna.
   • Use a DMM to record the voltage pulse using the MIN MAX setting to capture the AC voltage pulse to the passive antenna.

  1. Disconnect the keyless entry antenna - right at the exterior door handle.
  2. With the DMM measure/capture for an AC voltage signal between the keyless entry antenna signal circuit and the low reference circuit.
  3. With the scan tool, go to the RCDLR special functions menu. Select Right Door Handle Antenna
  4. Authenticate the antenna using the scan tool.

Was an AC voltage signal captured on the DMM?

Go to Step 7

Go to Step 5

5

Test both the keyless entry antenna signal and low reference circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 6

6

Inspect for poor connections at the RCDLR. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 8

7

Inspect for poor connections at the keyless entry antenna - right. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 10

8

Test the keyless entry antenna signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 9

9

Replace the RCDLR. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 12

--

10

Test both the keyless entry antenna signal and low reference circuit for a short to power. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

11

Replace the keyless entry antenna - right. Refer to Front Side Door Outside Handle Replacement in Doors.

Did you complete the replacement?

Go to Step 12

--

12
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the conditions for running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 3

System OK