OBD2 B2605: Immobilizer Disable Signal Open Circuit
The B2605 code indicates an open circuit in the disable signal wire of the vehicle's immobilizer or security module. This circuit carries the signal that allows or prevents engine starting, typically between the immobilizer module (NATS - Nissan Anti-Theft System) and the ECM/PCM. An open circuit means there is a break in electrical continuity, preventing the signal from reaching its destination. This can result in no-start conditions, intermittent starting, or the security indicator light staying on.
1. Commonly Affected Makes
2. Most Common Causes
- Damaged or corroded wiring in the disable signal circuit
- Loose, corroded, or disconnected immobilizer module connector
- Internal failure of the immobilizer module (NATS)
- Internal failure of the ECM/PCM receiving the signal
- Blown fuse in the immobilizer system power circuit
- Interference or modification in the wiring harness from previous repairs
3. Symptoms You Will Notice
- Engine cranks but does not start
- Intermittent starting issues
- Security indicator light stays on or flashes
4. Step-by-Step Diagnosis
Check for blown fuses related to the immobilizer system.
Inspect the disable signal circuit wiring and connectors for damage, corrosion, or looseness.
Test continuity of the disable signal wire between the immobilizer module and ECM/PCM.
Verify power and ground at the immobilizer module.
If wiring is intact, test the immobilizer module and ECM/PCM for internal faults using a scan tool.
5. Frequently Asked Questions
Is it safe to drive?▼
No, the vehicle may not start or may stall unexpectedly, posing a safety risk. It is recommended to have the issue diagnosed and repaired before driving.
How much does it cost to fix?▼
Repair costs typically range from $100 to $500, depending on whether the issue is a simple wiring repair or requires replacement of the immobilizer module or ECM.