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Home › Cadillac › 2007 › XLR Base › Repair and Diagnosis › Body & Frame › Door Locks › Keyless Entry System And Remote Functions › Diagnostic Information and Procedures › DTC B3121 › Test Description

Test Description

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

  1. 2:  Verifies that DTC B3121 is a current DTC.
  2. 3:  Testing for power and ground to the keyless entry antenna.
DTC B3121

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 B3121 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.
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 exterior rear compartment pad must be pressed to produce the 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 power circuit and the ground circuit.
Was an AC voltage signal 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. 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 - rear compartment. 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 - rear compartment. Refer to Ignition Lock Key Transmitter Antenna Replacement - Rear Compartment .
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
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