B2798
DTC B2796 or B2798
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC B2796
- No Communication in Immobilizer System
DTC B2798
- Communication Malfunction No. 2
Circuit Description
Embedded in the vehicle key is a transponder chip. This transponder chip contains unique values (codes) that are read by the theft deterrent key transponder during vehicle starting. The vehicle key has two codes: The key code (immobilizer code) and the wireless code. Both of these codes need to be registered before vehicle starting will be allowed. The theft deterrent key transponder receives the two transponder chip codes through the theft deterrent key transponder amplifier, which acts as a power source and antenna, passively powering the transponder chip and receiving the transponder chip codes.
Conditions for Running the DTC
The key is inserted into the ignition cylinder.
Conditions for Setting the DTC
There is no communication between the transponder chip and the theft deterrent key transponder.
Action Taken When the DTC Sets
Engine starting will be disabled.
Conditions for Clearing the DTC
The DTC will clear when the conditions for setting the DTC have been corrected.
Reference Information
Schematic Reference
Immobilizer Schematics (Immobilizer Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Immobilizer Description and Operation (Immobilizer Description and Operation)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Important: When using this diagnostic, more than one vehicle key is required to ensure proper diagnosis. If more than one key is not available at the time of service, contact the customer and ask if any other keys can be provided for service. If unavailable, a new second key can be created.
While viewing the scan tool Transponder Key parameter, turn ON the ignition with each of the available vehicle keys. The parameter should read OK with all available keys.
If only one key results in the parameter reading Error, replace the appropriate key.
If all available keys result in the parameter reading Not Present, refer to Circuit/System Testing.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the theft deterrent key transponder and the theft deterrent key transponder amplifier.
2. Ignition ON, test for less than 1V between the following signal circuit terminals at the theft deterrent key transponder harness connector and ground:
* Signal circuit terminal 4
* Signal circuit terminal 15
• If greater than the specified range, test the signal circuit for a short to voltage.
3. Ignition ON, test for infinite resistance between the following signal circuit terminals at the theft deterrent key transponder harness connector and ground:
* Signal circuit terminal 4
* Signal circuit terminal 15
• If not the specified value, test the signal circuit for a short to ground.
4. Test for less than 1ohm between the following signal circuit terminals:
* Signal circuit terminal 4 at the theft deterrent key transponder harness connector and signal circuit terminal 5 at the theft deterrent key transponder amplifier harness connector.
* Signal circuit terminal 15 at the theft deterrent key transponder harness connector and signal circuit terminal 4 at the theft deterrent key transponder amplifier harness connector.
• If greater than the specified range, test the signal circuit for an open/high resistance.
5. Replace the theft deterrent key transponder amplifier.
6. Clear all DTCs and attempt to start the vehicle. The vehicle should start and DTCs B2796 and/or B2798 should not set.
• If the vehicle does not start or either DTC is set, replace the theft deterrent key transponder.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Immobilizer System Component Programming (Programming and Relearning)
* Theft Deterrent Key Transponder Amplifier Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for theft deterrent key transponder replacement, setup, and programming