B1602 PATS Received Invalid Format of Key-Code from Ignition Key Transponder

Introduction:

The B1602 diagnostic trouble code (DTC) indicates a problem within a vehicle's Passive Anti-Theft System (PATS). Specifically, it signifies that the PATS module has received a key code from the ignition key transponder that is in an invalid or unrecognized format. This prevents the vehicle from starting, as the PATS module cannot verify the key's authenticity. Understanding the causes and troubleshooting steps for this code is crucial for resolving the no-start condition.

Comprehensive Table: B1602 PATS Received Invalid Format of Key-Code

Topic	Description	Possible Causes
PATS Overview	Electronic security system preventing unauthorized vehicle operation.	N/A - Background Information
B1602 Code Definition	PATS module received an invalid or unrecognized key code from the ignition key transponder.	N/A - Definition
Key Transponder Malfunction	The microchip embedded in the key that transmits the unique code to the PATS module is faulty.	Damaged transponder chip, Weak transponder signal, Incorrect transponder type, De-programmed transponder
Ignition Coil/Antenna Issue	The antenna surrounding the ignition switch that reads the key transponder signal is malfunctioning.	Damaged coil, Loose connection, Short circuit, Incorrectly installed aftermarket components
PATS Module Problems	The PATS module itself may be faulty, preventing it from correctly processing the key code.	Damaged module, Corrupted memory, Software glitches, Water damage, Electrical surges
Wiring/Connections	Wiring or connections between the key transponder, ignition coil/antenna, and PATS module are damaged or loose.	Corroded connectors, Broken wires, Short circuits, Open circuits, Poor grounding
Key Programming Issues	The key may not be properly programmed to the vehicle's PATS module.	Incomplete programming process, Using incorrect programming equipment, Key not compatible with vehicle
Aftermarket Security System Interference	Aftermarket security systems can sometimes interfere with the PATS system, causing communication errors.	Improper installation, Conflicting signals, Damaged aftermarket system, Incorrect wiring
Low Battery Voltage	Low battery voltage can sometimes cause erratic behavior in electronic modules, including the PATS module.	Weak battery, Faulty alternator, Parasitic drain, Loose battery terminals
Diagnostic Tools	Tools used to diagnose and reprogram PATS components.	N/A - Tools for troubleshooting
Troubleshooting Steps	Systematic approach to identify the root cause of the B1602 code.	Visual inspection, Key verification, Ignition coil testing, PATS module diagnostics, Wiring harness inspection, Battery voltage check

Detailed Explanations:

PATS Overview: The Passive Anti-Theft System (PATS) is an electronic security system designed to prevent unauthorized vehicle operation. It relies on a unique code embedded in the ignition key transponder, which must be recognized by the vehicle's PATS module for the engine to start.

B1602 Code Definition: The B1602 diagnostic trouble code (DTC) specifically indicates that the PATS module has received a key code from the ignition key transponder that is in an invalid or unrecognized format. This means the code transmitted by the key does not match the expected pattern or is corrupted in some way, preventing the vehicle from starting.

Key Transponder Malfunction: The key transponder is a small microchip embedded within the ignition key. This chip stores a unique code that is transmitted to the PATS module when the key is inserted into the ignition. A damaged transponder chip, a weak transponder signal (due to damage or interference), the use of an incorrect transponder type, or a de-programmed transponder can all lead to a B1602 code. Physical damage to the key, proximity to strong magnetic fields, or simple wear and tear can degrade the transponder's functionality.

Ignition Coil/Antenna Issue: The ignition coil, also sometimes referred to as the antenna, is located around the ignition switch. Its purpose is to read the signal emitted by the key transponder. If the coil is damaged, has a loose connection, a short circuit, or if incorrectly installed aftermarket components are interfering, it may not be able to properly read the key transponder signal, resulting in the B1602 code. Check the coil for physical damage and ensure its connection is secure.

PATS Module Problems: The PATS module is the central control unit of the anti-theft system. It receives the key code from the ignition coil/antenna and verifies its authenticity. A damaged module, corrupted memory within the module, software glitches, water damage, or electrical surges can all prevent the module from correctly processing the key code, leading to a B1602 code. These issues often require professional diagnosis and potentially module replacement or reprogramming.

Wiring/Connections: The wiring and connections between the key transponder, ignition coil/antenna, and PATS module are critical for proper communication. Corroded connectors, broken wires, short circuits, open circuits, or poor grounding can disrupt the signal flow and cause the B1602 code. Carefully inspect all wiring and connectors for any signs of damage or corrosion. Use a multimeter to check for continuity and proper voltage.

Key Programming Issues: The key must be properly programmed to the vehicle's PATS module for the system to recognize it. An incomplete programming process, using incorrect programming equipment, or attempting to use a key that is not compatible with the vehicle can all result in the B1602 code. Key programming typically requires specialized equipment and software. Consult a qualified locksmith or dealer.

Aftermarket Security System Interference: Aftermarket security systems can sometimes interfere with the PATS system, causing communication errors and triggering the B1602 code. This can be due to improper installation, conflicting signals between the two systems, damage to the aftermarket system, or incorrect wiring. If an aftermarket security system is installed, try temporarily disabling it to see if the B1602 code disappears. Ensure the aftermarket system is properly installed and compatible with the vehicle's PATS system.

Low Battery Voltage: Low battery voltage can sometimes cause erratic behavior in electronic modules, including the PATS module. This can be due to a weak battery, a faulty alternator, a parasitic drain on the battery, or loose battery terminals. A voltage drop can prevent the PATS module from operating correctly, leading to the B1602 code. Check the battery voltage and charging system to ensure they are functioning properly. A fully charged battery should read around 12.6 volts.

Diagnostic Tools: Various diagnostic tools are used to diagnose and reprogram PATS components. These include:

OBD-II Scanners: Read and clear diagnostic trouble codes (DTCs).
Key Programmers: Program new keys to the vehicle's PATS module.
Multimeters: Test voltage and continuity in wiring circuits.
Oscilloscopes: Visualize electrical signals to identify problems.

Troubleshooting Steps: A systematic approach is essential for identifying the root cause of the B1602 code:

Visual Inspection: Check the key, ignition switch, wiring, and connectors for any obvious signs of damage.
Key Verification: Try using a different key, if available, to see if the problem persists. If the second key works, the original key may be faulty.
Ignition Coil Testing: Test the ignition coil/antenna for continuity and proper resistance using a multimeter.
PATS Module Diagnostics: Use a diagnostic scanner to read any other DTCs related to the PATS system.
Wiring Harness Inspection: Carefully inspect the wiring harness for any signs of damage, corrosion, or loose connections.
Battery Voltage Check: Check the battery voltage to ensure it is within the normal range.

Frequently Asked Questions:

What does the B1602 code mean? It means the PATS module received an invalid key code from the ignition key transponder, preventing the vehicle from starting.
Can I fix the B1602 code myself? Simple issues like loose connections or a weak battery can be addressed, but more complex problems like a faulty PATS module or key programming usually require professional assistance.
How much does it cost to fix the B1602 code? The cost varies depending on the cause, but it can range from a simple key replacement to a more expensive PATS module replacement or reprogramming. Expect to pay anywhere from $50 to $500 or more.
Can I bypass the PATS system? Bypassing the PATS system is generally not recommended as it compromises the vehicle's security and may be illegal in some areas. It's best to address the underlying issue.
Will a dead battery cause the B1602 code? A severely low battery voltage can sometimes cause the PATS module to malfunction and trigger the B1602 code. Ensure your battery is properly charged.

Conclusion:

The B1602 code indicates a communication problem between the key transponder and the PATS module. A systematic troubleshooting approach, starting with basic checks and progressing to more advanced diagnostics, is crucial for identifying and resolving the underlying cause. If you are not comfortable performing these repairs yourself, it is best to seek the assistance of a qualified automotive technician or locksmith.