Experiencing a check engine light in your 2009 Subaru can be concerning. Fortunately, modern vehicles like your Subaru are equipped with an On-Board Diagnostic (OBD) system to help pinpoint potential issues. This system generates trouble codes that can be accessed using an OBD-II scanner, offering valuable insights into your vehicle’s health. Understanding these codes is the first step towards effective diagnosis and repair.
Decoding OBD2 Codes in Your 2009 Subaru
The OBD-II system in your 2009 Subaru monitors various components and systems, from the engine and transmission to emissions control. When a problem arises, the system stores a specific code, often referred to as a Diagnostic Trouble Code (DTC). These codes are standardized across most vehicles, but understanding the nuances for your 2009 Subaru is crucial.
Here’s a breakdown of common OBD2 codes you might encounter in your 2009 Subaru, along with potential causes:
| Code | Common Problems That Trigger This Code |
|---|---|
| P0010 | Variable Valve Timing Actuator Circuit (Bank 1): This could indicate issues with the Powertrain Control Module (PCM), a faulty variable valve timing actuator, or wiring problems affecting the actuator circuit. |
| P0011 & P0012 | “A” Camshaft Position – Timing Over-Advanced or Retarded (Bank 1): These codes often point to problems within the variable valve timing (VVT) system. Low engine oil level or pressure, incorrect engine timing, unsuitable engine oil, a failing VVT solenoid or actuator, or a worn timing chain can all contribute to these codes. |
| P0013 | Variable Valve Timing Actuator Circuit (Bank 2): Similar to P0010, but related to Bank 2 of the engine. Potential causes include PCM failure, a faulty VVT actuator, or wiring issues. |
| P0014 | “B” Camshaft Position – Timing Over-Advanced or System Performance (Bank 1): Mirrors P0011 and P0012, but may indicate issues with a different camshaft or a more severe timing discrepancy. Check for VVT solenoid or actuator problems, oil level/pressure, timing issues, incorrect oil type, or a worn timing chain. |
| P0101 | Mass Air Flow (MAF) Circuit Range/Performance: This code suggests a problem with the MAF sensor or the air intake system. Common culprits include vacuum leaks, a split intake air boot or PCV hose, defective intake manifold gaskets, a malfunctioning MAF sensor itself, wiring issues in the MAF sensor circuit, a faulty barometric pressure sensor, a dirty MAF sensor wire, or the need for a PCM software update. |
| P0102 | Mass Air Flow (MAF) Circuit Low Input: Usually indicates a problem with the MAF sensor circuit. Check for an unplugged or damaged MAF sensor, damaged wiring, loose or corroded terminals, or a faulty MAF sensor. |
| P0113 | Intake Air Temperature Circuit High Input: Points to a high reading from the Intake Air Temperature (IAT) sensor. This could be due to a defective IAT sensor, a dirty air filter restricting airflow, a defective MAF sensor (which often integrates the IAT sensor), or wiring/connection issues in the IAT sensor circuit. |
| P0128 | Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature): Indicates the engine coolant is not reaching the expected operating temperature. This is often caused by a defective engine thermostat, but could also be a faulty Engine Coolant Temperature Sensor, Intake Air Temperature Sensor, cooling system issues, low coolant level, dirty coolant, or a constantly running cooling fan. |
| P0135 | O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1): Signifies a problem with the heater circuit of the oxygen sensor. Potential causes range from a defective oxygen sensor itself, heater circuit issues, exhaust or intake air leaks, low fuel pressure, a faulty Engine Coolant Temperature Sensor, wiring problems, PCM software needing an update, or even a defective PCM. |
| P0171 & P0174 | System Too Lean (Bank 1 & Bank 2): These codes indicate that the engine is running lean, meaning there’s too much air and not enough fuel in the mixture. Common causes include vacuum leaks, a faulty MAF sensor, a plugged fuel filter or weak fuel pump, plugged or dirty fuel injectors, or the need for a PCM software update. |
| P0200, P0201, P0202, P0203, P0205 | Injector Circuit Malfunction (General & Cylinders 1, 2, 3, 5): These codes signal problems with the fuel injector circuits. This could involve a defective fuel injector, wiring or connection issues, a plugged injector, or dirt contamination in the fuel injector. |
| P0300, P0301, P0302, P0303, P0304 | Random/Cylinder Misfire Detected (General & Cylinders 1, 2, 3, 4): Misfires occur when one or more cylinders are not firing correctly. Numerous issues can cause misfires, including worn spark plugs, ignition wires, coils, distributor cap/rotor, incorrect ignition timing, vacuum leaks, low fuel pressure, EGR system problems, a defective MAF sensor, crankshaft/camshaft sensor issues, a faulty Throttle Position Sensor, or mechanical engine problems like low compression or valve issues. |
| P0401 | Exhaust Gas Recirculation (EGR) Flow Insufficient Detected: This code indicates insufficient EGR flow, often due to carbon buildup in the EGR passages. Other causes can be a defective EGR valve, vacuum or electrical signal problems to the EGR valve, a malfunctioning EGR vacuum supply solenoid, or issues with sensors that provide feedback to the computer about EGR system performance. |
| P0420 & P0430 | Catalyst System Efficiency Below Threshold (Bank 1 & Bank 2): These codes suggest that the catalytic converter is not functioning efficiently. This could be due to inefficient catalytic converters, defective oxygen sensors, or engine misfires. P0430 can also be triggered by internal engine damage leading to oil consumption and catalytic converter damage. |
| P0440, P0441, P0442, P0455 | Evaporative Emission Control System (EVAP) Faults: These codes relate to leaks or malfunctions in the EVAP system, which prevents fuel vapors from escaping into the atmosphere. Common causes include a missing or defective fuel cap, a damaged fuel filler neck, torn EVAP hoses, a defective fuel tank sending unit gasket, a split carbon canister, or issues with EVAP valves. |
| P0500 & P0501 | Vehicle Speed Sensor (VSS) Malfunction: These codes indicate problems with the Vehicle Speed Sensor or its circuit. This could be a defective VSS, speedometer issues, wiring or connector problems, CAN bus communication faults, or issues with the VSS drive gear in the transmission or differential. |
| P0505, P0506, P0507 | Idle Air Control (IAC) System Malfunction: These codes relate to the system that controls the engine’s idle speed. Potential causes include a defective IAC motor, vacuum leaks, carbon buildup in the throttle body, or a defective power steering pressure switch. |
| P0600, P0601, P0602, P0603, P0605 | PCM/ECM Internal Control Module Fault: These codes suggest internal problems with the Powertrain Control Module (PCM) or Engine Control Module (ECM). This can range from voltage supply issues, memory module failures, ground circuit problems, or CAN bus communication failures. These often require professional diagnosis and PCM replacement or reprogramming. |
| P0700, P0705, P0706, P0720, P0730 | Transmission Control System Malfunctions: These codes indicate various transmission-related issues. Common causes include defective shift solenoids, a faulty Engine Coolant Temperature Sensor (which can affect transmission operation), a defective valve body, dirty transmission fluid, or a defective Transmission Range Sensor. |
| P0841, P0842, P0845, P0846, P0847 | Transmission Fluid Pressure Sensor/Switch Circuit Range/Performance: These codes signal issues with the transmission fluid pressure sensor circuit. Low transmission fluid level, a faulty pressure sensor, wiring problems, or a TCM malfunction can be responsible. |
| P0901, P0935, P0942, P0944 | Clutch/Hydraulic System Faults: These codes are less common but can occur in specific Subaru models with specialized transmissions. They can indicate issues with the clutch master cylinder, clutch solenoid, hydraulic power unit, transmission filter, or transmission oil pump. |
| P0961 | Transmission Fluid Pressure Control Solenoid “A” Control Circuit Range/Performance: Points to a specific issue with the transmission shift solenoid control circuit. |
| P0A08, P0A0D, P0A0F, P0A7F, P0A80, P0B22, P0B24, P0B26, P0B28, P0B30, P0C00, P0C09, P0C11, P0C14, P0C15, P2000, P2002, P2004, P2006, P2101, P2122, P2135, P2138, P2181, P2210, P2213, P2237, P2238, P2251, P2302, P2303, P2305, P2308, P2310, P2401, P2402, P2422, P2431, P2432, P2500, P2501, P2503, P2509, P250C, P2601, P2607, P2609, P2610, P2614, P2706, P2711, P2714, P2716, P2723, P2803, P2806, P2809, P2810, P2815, P2A00, P2A01, P2A03, P2A04, P2BA8, P3000, P3100, P3400, P3401 | Various Powertrain Related Faults: This extensive range covers a multitude of less frequent powertrain related issues, from diesel particulate filter problems and intake manifold runner control to NOx sensor failures, ignition coil malfunctions, EVAP system leaks, and even hybrid/electric vehicle specific codes. These codes often require specialized diagnostic equipment for accurate troubleshooting. |
| B0081 | Driver Seatbelt Switch Circuit Malfunction: Indicates a problem within the driver’s side seatbelt system, potentially involving wiring, control module issues, or the airbag system itself. |
| C0040 & U0001 | Wheel Speed Sensor “A” Circuit Malfunction: These codes point to problems with a wheel speed sensor or its circuit, which is crucial for ABS and stability control systems. Causes can include a faulty sensor, wiring issues, reluctor ring problems, or ABS module faults. |
| U0073 | Control Module Communication Bus Off: Indicates a communication failure on the CAN bus network, which is used for communication between various vehicle modules. This can be due to a faulty control module or issues with the CAN bus wiring itself. |
| U0100 | Lost Communication With ECM/PCM “A”: Signals a loss of communication with the Engine Control Module (ECM) or Powertrain Control Module (PCM). This might be caused by a faulty PCM/ECM, circuit problems, or CAN bus issues. |
| U0107 & U0121 | Lost Communication With Throttle Actuator Control (TAC) Module / Anti-Lock Brake System (ABS) Control Module: These codes indicate a loss of communication with specific modules – the TAC module (responsible for electronic throttle control) or the ABS module. Potential causes include a dead battery, a faulty module, circuit problems, or CAN bus issues. |
When to Seek Professional Help for Your 2009 Subaru OBD2 Codes
While an OBD-II scanner provides a starting point, diagnosing and repairing your 2009 Subaru can sometimes be complex. Codes starting with “P1” are Subaru-specific and often require specialized knowledge and equipment to interpret accurately.
If you encounter any of the following, it’s best to consult with qualified Subaru technicians:
- **P1* codes: These manufacturer-specific codes often delve into deeper, Subaru-specific system nuances.
- Multiple codes: Several seemingly unrelated codes can indicate a more complex underlying issue.
- Unfamiliar codes: If you cannot find your specific code in readily available databases or online resources.
- Persistent codes after basic troubleshooting: If you’ve tried addressing the common causes for a code and it returns.
- Driveability issues: If your Subaru is experiencing performance problems like rough idling, stalling, or poor acceleration alongside the check engine light.
Our certified Subaru specialists at [cardiagnosticnearme.com] are equipped with advanced diagnostic tools and in-depth knowledge of 2009 Subaru models. We can accurately interpret your OBD2 codes, perform thorough diagnostics, and provide reliable repairs to get you back on the road with confidence.
Don’t let a check engine light concern you. Contact us today at 720-912-3655 or schedule a service appointment online to have your 2009 Subaru diagnosed and expertly serviced.
