GM Service Manual Online
For 1990-2009 cars only

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 B3120 02: Keyless Entry Antenna 2 Performance Short to Ground

DTC B3120 05: Keyless Entry Antenna 2 Performance Short to Battery or Open

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Keyless Entry Antenna - Signal (4)

B3119 02

B3119 05

B3119 05

--

Keyless Entry Antenna - Low Reference (4)

--

B3119 05

--

--

Keyless Entry Antenna - Signal (5)

B3120 02

B3120 05

B3120 05

--

Keyless Entry Antenna - Low Reference (5)

--

B3120 05

--

--

Keyless Entry Antenna - Signal (3)

B3121 02

B3121 05

B3121 05

--

Keyless Entry Antenna - Low Reference (3)

--

B3121 05

--

--

Keyless Entry Antenna - Signal (2)

B3123 02

B3123 04

B3123 04

--

Keyless Entry Antenna - Low Reference (2)

--

B3123 04

--

--

Keyless Entry Antenna - Signal (1)

B3123 02

B3123 04

B3123 04

--

Keyless Entry Antenna - Low Reference (1)

--

B3123 04

--

--

Keyless Entry Active Antenna Supply Voltage

B3122 04

B3122 04

B3122 04

--

Keyless Entry Active Antenna Data Signal

B3122 04

B3122 04

B3122 04

--

Keyless Entry Active Antenna Clock Signal

B3122 04

B3122 04

B3122 04

--

Keyless Entry Active Antenna Low Reference

--

B3122 04

--

--

Circuit/System Description

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

Conditions for Running the DTC

A transmitter validation is requested.

Conditions for Setting the DTC

An improper voltage level is seen on the keyless entry antenna - signal (5) circuit.

Action Taken When the DTC Sets

The RF door handle antenna is ignored.

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 50 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

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

  1. Ignition OFF, disconnect the harness connector at the RF door handle antenna.
  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 RCDLR.
  4. Install a DMM between the signal circuit terminal 1 and the low reference circuit terminal 2. Set the DMM to capture AC voltage using the MIN MAX function.
  5. Pull the RF door handle. Verify the DMM captured an AC voltage signal.
  6. If an AC voltage was not captured, test the signal circuit and the low reference circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the RCDLR.
  7. If all circuits test normal, test or replace the LF door handle assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Front Side Door Outside Handle Replacement
    •  Control Module References for RCDLR replacement, setup, and programming