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Test Description

WARNING: This page is about a different car, the 2006 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  Verifies that DTC B3121 is a current DTC.
  2. 3:  Verifies that the exterior rear compartment lid release pad is operating properly. A valid input from the lid release pad is required by the RCDLR to authenticate the antenna.
  3. 4:  Testing for power and ground to the keyless entry antenna.
DTC B3121

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 B3121 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 trunk release switch parameter in the remote control door lock receiver (RCDLR) miscellaneous inputs data list.
  2. Operate the exterior rear compartment lid release pad.
Does the trunk release switch state display INACTIVE?		 Go to Trunk Release Inoperative (Interior Release Inoperative) or Trunk Release Inoperative (Exterior Release Inoperative) in Body Rear End 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 - rear compartment at the rear compartment latch area.
  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 Rear Fascia 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 - rear compartment. 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 10 
11 Replace the keyless entry antenna - rear compartment. Refer to Remote Control Door Lock and Theft Deterrent Receiver Replacement .
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
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