For 1990-2009 cars

### Circuit Description

Synchronization may be necessary under the following conditions:

• | If the immobilizer programming procedure has been performed.

• | If the transmitter is activated more than 255 times while the transmitter is out of range of the intelligent switching unit antenna.

• | Synchronization may be necessary due to the security method used by the remote keyless entry system. The transmitter does not send the same signal twice to the intelligent switching unit (ISU).

• | The ISU will not respond to a signal that has been sent previously. This prevents anyone from recording and playing back the signal from the transmitter.

• | The battery in the transmitter was replaced.

• | The battery in the vehicle has been in a low or no charge condition for an extended period of time.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC 024 Keyless Entry Transmitter Synchronization Failure

### Conditions for Running the DTC

Vehicle battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

• | The immobilizer programming procedure has been performed.

• | The transmitter is activated more than 255 times while the transmitter is out of range of the intelligent switching unit's antenna.

• | Synchronization may be necessary due to the security method used by the remote keyless entry system. The transmitter does not send the same signal twice to the ISU.

• | The ISU will not respond to a signal that has been sent previously. This prevents anyone from recording and playing back the signal from the transmitter.

• | The battery in the transmitter was replaced.

• | The battery in the vehicle has been in a low or no charge condition for an extended period of time.

### Action Taken When the DTC Sets

The remote function control will be inoperative.

### Conditions for Clearing the DTC

• | The ISU no longer detects an out of synchronization condition from the key fob.

• | A history DTC will clear after 40 consecutive ignition cycles if the condition for the malfunction is no longer present.

Step | Action | Yes | No
--- | --- | --- | ---
Important: You must obtain all the keys from the vehicle owner before testing any current keys. If a key needs to be replaced, any vehicle keys not programmed during the programming procedure will be inoperative after the programming sequence is completed. Ensure that the doors, hood and trunk/rear hatch are closed prior to starting the programming procedure. If the system is placed in program mode, then the ISU will erase all previously programmed transmitters upon the receipt of the first transmitter s programming signal. Do not operate or program the transmitters in the vicinity of other vehicles that are also in the keyless entry program mode. This prevents the programming of the transmitters to the incorrect vehicle.
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Perform the Transmitter Synchronization procedure to the suspect key fob. Refer to Transmitter Synchronization .
2. Test the key fob for proper operation. Refer to Keyless Entry System Description and Operation .

Did you find and correct the condition?

System OK

Go to Symptoms - Keyless Entry