GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2007 🢒 XLR 🢒 DTC 🢒 DTC B3122

Circuit Description

The keyless entry antenna - back up is located in the glove compartment area and is used as a short range low frequency (LF) transmitter. When a valid key fob is within the passenger compartment and the brake pedal is depressed and the ignition button is pressed the keyless entry antenna transmitter broadcasts a challenge within the passenger compartment to the key fob. If the response from the key fob via radio frequency (RF) is a valid response and all the security requirement are met the vehicles engine will start or be able to go into accessory mode.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B3122 Keyless Entry Antenna 4 Performance

Conditions for Setting the DTC

The remote control door lock receiver (RCDLR) will set this DTC during antenna activation if the keyless entry antenna - back up is open, or has a high resistance. The RCDLR can only set a DTC when it is the vehicle system voltage is between 9-16 volts.

Action Taken When the DTC Sets

The RCDLR will set and store a DTC B3122.

Conditions for Clearing the DTC
    • The RCDLR no longer detects an open or a high resistance 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. This step verifies that DTC B3122 is a current DTC.

    2.

  2. This step tests for power and ground to the keyless entry antenna.

Step

Action

Yes

No

Schematic Reference: Remote Function Schematics

Connector End View Reference: Remote Function Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Important: To achieve service by pass mode, key ON engine OFF, a programmed key fob 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 B3122 as a current DTC?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3

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.
   • The ignition start button must be pressed to produce the voltage pulse to the passive antenna.
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.

Important: Use a DMM to record the voltage pulse using the MIN MAX setting to capture the AC voltage pulse to the passive antenna.

Important: The ignition start button must be pressed to produce the voltage pulse to the passive antenna.

  1. Disconnect the keyless entry antenna - back up at the glove compartment area.
  2. With the DMM measure/capture for an AC voltage signal between the keyless entry antenna power circuit and the ground circuit.

Was an A/C voltage signal greater than 1.2 V captured on the DMM?

Go to Step 6

Go to Step 4

4

Test both the keyless entry antenna power and ground circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

Go to Step 11

Go to Step 5

5

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

Did you find and correct the condition?

Go to Step 11

Go to Step 7

6

Inspect for poor connections at the keyless entry antenna - back up. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.

Did you find and correct the condition?

Go to Step 11

Go to Step 9

7

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

Did you find and correct the condition?

Go to Step 11

Go to Step 8

8

Replace the RCDLR. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 11

--

9

Test both the keyless entry antenna power and ground circuit for a short to power. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

10

Replace the keyless entry antenna - back up. Refer to Ignition Lock Key Transmitter Antenna Replacement - Instrument Panel .

Did you complete the replacement?

Go to Step 11

--

11
  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