Key Fob Not Detected. Cadillac STS 2005

GM Service Manual Online

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 Engine 🢒 Engine Electrical 🢒 Key Fob Not Detected

Step

Action

Yes

Schematic Reference: Keyless Entry Schematics

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Does the customer complain about other symptoms related to this, such as poor range when the key fob buttons are pressed or intermittent Tire Pressure Monitoring issues? (It’s possible the RF External Antenna at the RCDLR may have a poor connection.)

Go to Step 3

Go to Step 4

Inspect the external RF antenna connection at the RCDLR. First, gently pull on the coax connector at the module. If the coax comes out, then it wasn’t seated properly. Remove and carefully inspect the coax connection for bent blades or a bent center pin. Fix coax connection if necessary and re-seat connector until a "click" is heard. Gently pull on the coax connection to make sure it is seated properly. Was the inspection made?

Go to Step 4

Go to Step 3

Important: This condition may be caused by a low vehicle battery voltage. If the battery is not sufficiently charged (above 10 volts), the system will have difficulties detecting the fob and the NO FOBS DETECTED message will be displayed. Correct the low battery voltage condition to eliminate this condition.

With a valid key fob, attempt to start the vehicle.

Is the NO FOB DETECTED message displayed on the driver information center (DIC)?

Go to Step 5

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

Exit the vehicle with the key fob.
Lock the vehicle.
Attempt to enter both the driver and passenger doors passively with the key fob.

Are you able to enter the vehicle from both doors?

Go to Step 6

Go to Keyless Entry System Inoperative

Important: Areas of high radio frequency (RF) traffic may cause an intermittent NO FOB DETECTED message. This is a normal condition. If the vehicle is parked in an area of high RF traffic, move vehicle before continuing with diagnostics.

Move the key fob to various places within the vehicle and attempt to start.

Does the vehicle start?

System OK

Go to Step 7

Place the key fob in the limp home pocket located in the center console.
Turn ON the ignition with the engine OFF by pressing and holding the ACC button for 5 seconds.
Connect a scan tool to the vehicle.
Check vehicle for any DTCs.

Were any DTCs found?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 8

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

Disconnect the console antenna at the center console.
With the keyless entry transmitter held near the headliner antenna, press the ignition start button.

Does the vehicle start?

Go to Step 10

Go to Step 9

Important:

•	The voltage signal sent by the remote control door lock receiver (RCDLR) to the passive antenna is an 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.

Disconnect the headliner antenna.
With the DMM measure/capture for an AC voltage signal between the keyless entry signal circuit and the low reference circuit.

Was an AC voltage signal captured on the DMM?

Go to Step 14

Go to Step 11

Important:

•	The voltage signal sent by the RCDLR to the passive antenna is an AC voltage signal. The DMM must be set on AC voltage setting to record the voltage pulse to the console 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.

With the DMM, measure/capture for an AC voltage signal between the console passive keyless entry antenna signal circuit and the low reference circuit.

Was an AC voltage signal captured on the DMM?

Go to Step 15

Go to Step 12

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

Did you find and correct the condition?

Go to Step 19

Go to Step 13

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

Did you find and correct the condition?

Go to Step 19

Go to Step 13

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 19

Go to Step 14

Inspect for poor connections at the headliner antenna. 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 19

Go to Step 15

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