• 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.

The keyless entry transmitter is part of the vehicle key. The keyless entry system will unlock the vehicle doors or open/unlock the rear compartment when a corresponding button on the keyless entry transmitter is pressed. This is accomplished by the keyless entry transmitter sending a radio frequency to the remote control door lock receiver, which then sends the signal to the body control module (BCM). The BCM interprets the signal and activates the requested function. A low transmitter battery or radio frequency (RF) interference from aftermarket devices such as 2-way radios, power inverters, cellular phone chargers, computers, etc. may cause a system malfunction. High RF traffic areas, such as gas stations which use pay-at-the-pump RF transponders, may also cause interference that could lead to a malfunction.

• Unwanted or inadvertent door lock/unlock activation may be requested by the OnStar® Remote Link app. It is possible that a customer may be unaware of account usage, result in an unwanted or phantom door lock/unlock. If normal system diagnosis does results in an inability to verify the customer’s concern, contact Technical Assistance Center (TAC).
• If available, the EL 43241 Keyless Entry Tester may be used to diagnose a low transmitter battery or a malfunctioning transmitter. To test, place the transmitter on the test pad of the EL 43241 and press each transmitter button one at a time, holding each button for three seconds. If the green light on the tester does not illuminate and a tone does not sound, first replace the transmitter battery and retest. If the malfunction continues after replacing the transmitter battery, replace the transmitter.
• When using the EL 43241 Keyless Entry Tester, first inspect the keyless entry transmitter part number to determine that it is the correct model for the vehicle. An incorrect part number transmitter may pass the test, but it will not activate the keyless entry system.
• When the vehicle key is in the ignition, the keyless entry functions are disabled from all keyless entry transmitters.

Remote Function Schematics

Master Electrical Component List

Keyless Entry System Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for K9 Body Control Module scan tool information

EL 43241 Keyless Entry Tester

1. Verify the Tire Pressure Monitoring System is functioning by adding air to one tire to see the air pressure display increase.
• If the pressure does not increases

  Refer toSymptoms - Tire Pressure Monitoring

• If the pressure increases
2. Verify the VIN information for the vehicle transmitter is correct using theEL-52545 .
• If the VIN is blank

  Refer to Remote Control Door Lock and Theft Deterrent Transmitter Programming.

• If the VIN is incorrect

  This transmitter is not for this vehicle, it may already be programmed to work with a different vehicle but cannot be programmed to this vehicle.

• If the VIN is correct
3. Verify the frequency of the transmitter matches the frequency of the tire pressure monitoring system and the remote control door lock receiver using the EL-52545 .
• If the transmitter frequency is incorrect

  Replace the vehicle transmitter.

• If the transmitter frequency is correct
4. Verify the part number information for the vehicle transmitter is correct using the EL-52545 .
• If the vehicle transmitter part number is incorrect

  Replace the vehicle transmitter.

• If the vehicle transmitter part number is correct
5. Verify the transmitter output is above 20% on theEL-52545 signal strength meter by pressing a button on the transmitter ten times.
• If the transmitter output is lower than 20%

  Replace the transmitter battery.

Note: Before replacing the transmitter, inspect the transmitter battery contacts for any corrosion or damage. If no corrosion or damage is found, replace the transmitter battery and retest before replacing the transmitter. For transmitter battery replacement refer to Remote Keyless Entry (RKE) System Operation in the owner manual.

• If the transmitter output is higher than 20%
6. Using the scan tool read the number of transmitters learned in the K9 Body Control Module. Using theEL-52545 read the number of transmitters learned in the transmitter.
• If the transmitters learned is less than the number programmed

  Program the transmitter. Refer to Remote Control Door Lock and Theft Deterrent Transmitter Programming.

• If the transmitters learned is equal to the number programmed
7. Lock the vehicle using the keyless entry transmitter.
• If either the doors or the rear compartment do not unlock/unlatch and open

  Refer to Circuit/System Testing.

• If both doors and the rear compartment unlock/unlatch and open
8. The concern may be caused by temporary RF interference. Discuss the conditions in which the concern occurs with the customer. RF interference from aftermarket devices such as 2-way radios, power inverters, cellular phone chargers, computers, etc. may cause a system malfunction. High RF traffic areas, such as gas stations which use pay-at-the-pump RF transponders, may also cause interference that could lead to a malfunction.

1. Ignition OFF and all vehicle systems OFF, scan tool disconnected, disconnect the harness connector at the K77 Remote Control Door Lock Receiver. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 30 Ω between the low reference circuit terminal 1 and ground.
• If 30 Ω or greater
1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the K9 Body Control Module.
• If less than 30 Ω
3. Ignition ON.
4. Test for greater than 11.5 V between the B+ circuit terminal 4 and ground.
• If 11.5 V or less
1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If Infinite resistance.
3. Test for less than 2 Ω in the B+ circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the K9 Body Control Module.
• If greater than 11.5 V
5. Test for 0.001–12 V between the serial data circuit terminal 2 and ground.
• If less than 0.001 V
1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the serial data circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 Ω in the serial data circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the K9 Body Control Module.
• If greater than 12 V
1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 0.001 V between the serial data circuit and ground.
• If 0.001 V or greater, repair the short to voltage on the circuit.
• If less than 0.001 V, replace the K9 Body Control Module.
• If between 0.001–12 V
6. Ignition OFF, disconnect the X1 and X2 harness connectors at the K9 Body Control Module, ignition ON.
7. Test for less than 0.001 V between the K9 Body Control Module serial data circuit terminal 26 X1 and ground.
• If 0.001 V or greater

  Repair the short to voltage on the circuit.

• If less than 0.001 V
8. Ignition OFF.
9. Test for infinite resistance between the K9 Body Control Module serial data circuit terminal 26 X1 and ground.
• If less than infinite resistance

  Repair the short to ground on the circuit.

• If infinite resistance
10. Test for less than 2 Ω between the K9 Body Control Module serial data circuit terminal 26 X1 and the K77 Remote Control Door Lock Receiver serial data circuit terminal 3.
• If 2 Ω or greater

  Repair the open/high resistance in the circuit.

• If less than 2 Ω
11. Replace the K77 Remote Control Door Lock Receiver. Refer toRemote Function Actuator Module Replacement
12. Verify the keyless entry functions operate.
• If the keyless entry functions do not operate

  Replace the K9 Body Control Module

• If the keyless entry functions operate
13. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

• Key with Integrated Transmitter Programming
• Control Module References for module replacement, programming, and setup