Owner's Problem Description
The owner reports that the power windows and locks on their 2009 Nissan Altima flickered and then stopped working entirely. After replacing the fuses, the problem persists, with none of the windows operating and the locks stuck in the up position. The owner attempted to reset the system by disconnecting the battery, but this did not resolve the issue. They noted that there is no relay associated with the power windows and locks. The current condition is that all four doors remain non-functional.
Professional Technical Analysis
The 2009 Nissan Altima equipped with a standard power window and lock system can experience intermittent failures due to several interconnected components. With an estimated mileage of around 100,000 miles, the vehicle's electrical system may show signs of wear, particularly in the wiring harness and body control module (BCM). The initial symptom of flickering lights suggests a potential electrical issue, possibly stemming from poor connections or short circuits within the power window/lock system. Upon further investigation, the power window and lock failure could be traced back to the BCM, which manages the operation of these components. A common failure mode for the BCM is a software glitch or internal component failure, often indicated by the presence of Diagnostic Trouble Codes (DTCs) when scanned. The vehicle's current condition raises safety concerns, as non-operational windows and locks can impede emergency exits and theft prevention. Technically, the power window system operates at 12V, and proper voltage readings should be confirmed across the relevant circuits. The absence of relay involvement in this system means that direct wiring or the BCM is likely the source of the issue. Given the complexity of the integrated systems in modern vehicles, a systematic approach to diagnostics is essential for efficient troubleshooting.
Possible Causes
Most common causes (ordered by frequency):
- Body Control Module (BCM) Failure: The BCM manages the power window and lock functions. Failure can occur due to internal component issues or software glitches, commonly leading to the complete inoperability of these systems. Testing the BCM's power and ground circuits is critical, with expected voltage readings around 12V. If the BCM is found faulty, replacement (OEM P/N 284B1-9N00A) is necessary, typically costing between $200-$400 with labor estimated around 2-3 hours. - Symptoms include complete failure of all power windows and locks, no response from switches, and potential DTCs related to BCM failure. A scan may reveal codes such as B2610 (BCM Internal Failure).
- Wiring Harness Issues: Over time, wiring that connects the BCM to the power window and lock systems can become damaged due to wear, corrosion, or rodent activity. Resistance in these circuits should be checked, with acceptable resistance values typically under 5 ohms. If any wiring damage is found, repairs or replacements are necessary, which can cost between $100-$300 depending on the extent of the damage. - Flickering lights initially suggest poor connections; visual inspection may reveal frayed wires or corrosion at connectors. Testing for continuity in critical wiring should be done.
- Fuse Box Issues: The power windows and locks may not be functioning due to a blown fuse or poor connections within the fuse box. The main fuse for these systems is often a 40 amp fuse (P/N 24066-3TA0A). Testing the fuses for continuity and ensuring proper contact within the fuse box is essential, with replacement costs typically around $10-$20. - Owner reported replacing fuses but may not have checked all related fuses. Visual inspection of the fuse box could reveal burnt fuses or poor connections.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Initial OBD-II Diagnosis: Use a professional OBD-II scanner or GeekOBD APP to perform a complete scan of the BCM for any stored DTCs. Pay particular attention to codes related to the power window and lock systems, as these will guide further diagnostics. Check for freeze frame data that may provide context for the failures.
- STEP 2 - Electrical System Inspection: Visually inspect the wiring harness for any signs of wear or damage, particularly at connector points. Use a multimeter to check for continuity and proper voltage at the BCM input and output terminals, expecting around 12V. Repair any damaged wiring as necessary.
- STEP 3 - Fuse and Relay Check: Inspect the fuse box for any blown fuses and ensure proper connections. Test the main fuse (40 amp) for continuity with a multimeter. If the fuse is good, verify that there is no corrosion in the fuse box. Replace any faulty fuses with OEM replacements.
- STEP 4 - BCM Testing: If previous steps do not reveal faults, consider testing the BCM itself. Check for proper voltage supply to the BCM and use a scan tool to check for any internal failures. If the BCM is found to be faulty, replace it using OEM part (P/N 284B1-9N00A) and recheck the system operation.
