Experiencing a no start, no crank, and no OBD2 communication issue with your 2010 WRX can be incredibly frustrating. When your Subaru WRX refuses to even crank, let alone start, and you can’t pull any diagnostic trouble codes because the OBD2 scanner won’t connect, it can feel like you’re facing a brick wall. This situation, particularly common in models like the 2010 WRX, points to a deeper electrical or sensor problem preventing the engine from even attempting to turn over. Let’s delve into the potential causes and troubleshooting steps for a 2010 WRX exhibiting these exact symptoms: no start, no crank, and no OBD2 connectivity.
Understanding “No Start, No Crank, No OBD2”
To properly diagnose this issue on your 2010 WRX, it’s crucial to understand what each symptom signifies:
- No Start: The engine fails to ignite and run. This is the overarching problem.
- No Crank: When you turn the ignition key, you hear absolutely nothing. The starter motor doesn’t engage, and the engine does not attempt to turn over. This immediately suggests a problem preventing the engine from even beginning the starting process.
- No OBD2 Communication: Your OBD2 scanner cannot establish a connection with the car’s computer (ECU). This is a significant clue, indicating a potential power or communication issue affecting the ECU and related systems.
The combination of these three symptoms in a 2010 WRX strongly suggests a problem that is fundamental to the vehicle’s electrical system or critical engine management components. It moves beyond simple ignition or fuel delivery issues and points towards problems that are preventing the car’s computer from even initializing the starting sequence.
Common Causes for a 2010 WRX No Start, No Crank, No OBD2 Issue
Several potential culprits can lead to a 2010 WRX experiencing a no start, no crank, and no OBD2 communication situation. Let’s explore the most likely causes:
Battery and Electrical System Problems
The most basic yet often overlooked cause is a dead or severely discharged battery. Without sufficient power, the starter motor won’t crank, the ECU won’t power up to communicate with the OBD2 scanner, and naturally, the engine won’t start.
- Dead Battery: Test the battery voltage with a multimeter. A healthy battery should read around 12.6 volts at rest. If it’s significantly lower, the battery might be dead or too weak to start the car.
- Loose or Corroded Battery Terminals: Check the battery terminals for secure connections and corrosion. Clean any corrosion with a wire brush and ensure the terminals are tightly fastened.
- Blown Fuses: Crucial fuses related to the ECU, ignition, and starter systems might be blown. Consult your 2010 WRX owner’s manual for fuse box diagrams and check fuses relevant to these systems. Pay close attention to the main fuses and those associated with the ECU and ignition.
- Faulty Ignition Switch: Although less common, a faulty ignition switch can prevent power from reaching the necessary circuits to start the car and power the OBD2 port.
Starter Motor Issues
If the electrical system seems sound, the next area to investigate is the starter motor itself.
- Faulty Starter Motor: The starter motor might be internally damaged or have a failing solenoid. Since you have a “no crank” condition, the starter motor’s ability to engage and turn the engine is directly in question.
- Starter Relay: A malfunctioning starter relay can prevent power from reaching the starter motor. Locate the starter relay (refer to your owner’s manual) and try swapping it with an identical relay from a less critical system (like the horn relay) to see if it resolves the no crank issue.
Crankshaft Position Sensor (CKP) Failure
The crankshaft position sensor (CKP) is a critical component for engine operation. It tells the ECU the position and rotational speed of the crankshaft, which is essential for ignition and fuel injection timing. A faulty CKP sensor can absolutely cause a no start and potentially a no crank condition in some systems, and it can also interfere with OBD2 communication in certain failure modes.
- CKP Sensor Malfunction: If the CKP sensor fails or its signal is interrupted, the ECU won’t know the crankshaft’s position and will prevent the engine from starting. In some cases, a faulty CKP can also disrupt the ECU’s ability to communicate, leading to no OBD2 connectivity.
- Wiring and Connections: Inspect the CKP sensor wiring and connector for damage, breaks, or corrosion. A wiring issue can also mimic a sensor failure.
Camshaft Position Sensor (CMP)
While less likely to cause a “no crank” condition directly, a faulty camshaft position sensor (CMP) can also lead to a no start situation. The CMP sensor works in conjunction with the CKP sensor to provide precise engine timing information.
- CMP Sensor Issues: A failing CMP sensor can disrupt the engine’s starting process. However, it is less likely to be the primary cause of a “no crank” and no OBD2 communication scenario compared to a CKP sensor or electrical issues.
Timing Belt/Chain Problems
Although less common, a jumped timing belt or chain can cause a no start condition. In severe cases, it might contribute to a no crank situation if the engine is mechanically locked up (though this is less likely with a jumped timing belt/chain and more likely with catastrophic engine failure).
- Jumped Timing Belt/Chain: If the timing belt or chain has jumped teeth, the crankshaft and camshafts will be out of sync, preventing the engine from starting. This is more likely to result in a no start crank situation, but it’s worth considering, especially if the vehicle has high mileage or the timing belt service interval is overdue.
ECU Issues and Green Diagnostic Connectors
The original forum post mentions “green connectors under the dash.” These are indeed diagnostic connectors used by dealerships and for ECU reflashing.
- Green Diagnostic Connectors Connected: If these green connectors are accidentally connected, it can cause unusual electrical behavior and potentially interfere with normal ECU operation, although it’s unlikely to directly cause a no crank and no OBD2 communication situation. It’s worth checking to ensure they are disconnected, but this is a less probable cause for the specific symptoms described.
- ECU Malfunction: While rare, the ECU itself could be faulty. However, before suspecting ECU failure, rule out all other more common causes. ECU failure is usually a diagnosis of last resort.
Immobilizer/Anti-theft System
In some cases, a problem with the vehicle’s immobilizer or anti-theft system could prevent starting and potentially OBD2 communication.
- Immobilizer Issues: If the immobilizer system is malfunctioning or not recognizing the key, it can prevent the engine from starting and cranking. This is less likely to cause no OBD2 communication, but it’s a possibility to consider, especially if any aftermarket anti-theft systems are installed or if there are issues with the key transponder.
Diagnosing the Issue Systematically
Instead of randomly replacing parts, a systematic diagnostic approach is crucial to pinpoint the root cause of your 2010 WRX’s no start, no crank, no OBD2 communication problem.
- Battery Check: Start with the battery. Use a multimeter to check the voltage and ensure terminals are clean and tight. Try jump-starting the car to rule out a dead battery definitively.
- Fuse Inspection: Thoroughly inspect all relevant fuses in both the engine bay and interior fuse boxes. Replace any blown fuses with the correct amperage rating.
- Starter System Check: If fuses are good and battery is charged, listen for a click from the starter solenoid when turning the key. If there’s no click, suspect the starter relay or the starter motor itself. You can try bypassing the starter relay (with caution and proper knowledge) to see if the starter motor engages.
- CKP Sensor Inspection: Locate the crankshaft position sensor (usually near the crankshaft pulley or flywheel). Inspect its wiring and connector for damage. Testing the CKP sensor often requires a multimeter or oscilloscope and understanding the sensor’s specifications, which might be best left to a professional if you’re not experienced.
- OBD2 Port Power and Ground Check: Use a multimeter to check if the OBD2 port is receiving power and ground. Pin 16 should have battery voltage, and pins 4 and 5 should be ground. If there’s no power or ground at the OBD2 port, trace back the wiring to identify the break or issue.
- Consult a Factory Service Manual (FSM): A Factory Service Manual for your 2010 WRX provides detailed wiring diagrams, diagnostic procedures, and component locations, which are invaluable for troubleshooting complex electrical issues.
Conclusion
Dealing with a 2010 WRX that exhibits no start, no crank, and no OBD2 communication requires a methodical approach. By systematically checking the battery, electrical system, starter components, and critical sensors like the CKP sensor, you can narrow down the potential causes. Remember to prioritize safety and consult a professional mechanic if you are not comfortable performing these diagnostic steps yourself. Avoid simply swapping parts blindly; a proper diagnosis is always the most efficient and cost-effective way to get your 2010 WRX back on the road.
