The illuminated check engine light is always a source of concern. When the code Fault Code P1395 appears on your diagnostic tool screen, it is crucial to understand that it is a manufacturer-specific code. Its meaning varies significantly depending on your vehicle’s make and model. This article guides you through understanding, diagnosing, and resolving this issue.
Meaning of Code P1395
The Fault Code P1395 is a generic OBDII (On-Board Diagnostics II) code, but its precise definition is determined by the automobile manufacturer. There are two main, almost opposite, interpretations:
- Camshaft Position Sensor (CMP) Problem – The most common:
- Definition: “Intermittent Camshaft Position (CMP) Sensor Signal Error” or “CMP Sensor Circuit Performance Problem”.
- Function: The CMP sensor informs the engine control unit (ECU) of the exact position of the camshafts to perfectly synchronize fuel injection and ignition spark.
- Oxygen Sensor (O2 Sensor) Problem – Specific to Honda/Acura:
- Definition: “Incorrect signal from the secondary oxygen sensor (downstream sensor) – Bank 1, Sensor 2”.
- Function: This sensor, located after the catalytic converter, monitors its efficiency. An abnormal signal triggers the code.
⚠️ Warning: The first essential step is to consult the repair manual or a reliable database specific to your vehicle (make, model, year, engine) to know the exact definition.
Symptoms of Code P1395
Symptoms vary radically depending on the underlying cause.
If the problem is with the CMP Sensor (Camshaft):
- Hard starting or failure to start: The ECU no longer knows when to trigger injection or ignition.
- Engine stalling: The engine may stall unpredictably, at idle or low speed.
- Irregular idle and rough engine: The engine shakes and runs very erratically.
- Loss of power and hesitation during acceleration.
- Check engine light illuminated.
If the problem is with the Oxygen Sensor (for Honda):
- Check engine light illuminated (often the only symptom).
- Increased fuel consumption (slight).
- Failure of emissions test.
- Engine performance is often normal.
Possible Causes of Fault P1395
Causes related to the CMP Sensor (most frequent):
- Faulty CMP Sensor: The most common cause. The sensor is worn out or burnt.
- Wiring problem: Damaged, chafed, cut wires, or wires chewed by rodents between the sensor and the ECU.
- Faulty connector: Oxidized connector (moisture, salt), loose, or with bent or corroded pins.
- Dirty or damaged target or reluctor wheel: The toothed wheel read by the sensor may be damaged, dirty, or have a missing tooth.
- Timing problem: Misaligned timing belt or one that has jumped a tooth (less frequent).
Causes related to the Oxygen Sensor (Honda/Acura):
- Faulty Oxygen Sensor (Bank 1, Sensor 2 – downstream sensor).
- Damaged sensor wiring or connector.
- Exhaust leak upstream of the sensor, distorting measurements.
Diagnosis and Solutions
General Diagnostic Steps:
- Clear the code and perform a road test: Use your diagnostic tool. If the code returns immediately, the problem is persistent. If it returns after several kilometers/miles, it is intermittent (often related to wiring).
- Visual Inspection (CRUCIAL):
- Locate the component in question (CMP sensor or downstream oxygen sensor) using a repair manual.
- Disconnect the battery before any handling.
- Inspect the connector and wiring meticulously along their entire visible length. Look for signs of burning, corrosion, chafing, or damage.
- Cleaning connections: Clean the connectors with an electrical contact cleaner and reconnect them firmly.
Specific Tests:
For the CMP Sensor:
- Resistance test: Using a multimeter, measure the sensor’s resistance (Ω). Compare the obtained value with that specified in the repair manual. A value outside the norm indicates a faulty sensor.
- Signal test: Using an oscilloscope, observe the sensor’s signal. An irregular or absent signal confirms the failure.
For the Oxygen Sensor (Honda):
- Real-time data: Use an OBD2 scanner capable of reading live data. Observe the voltage of the downstream sensor (S2). A stable voltage that does not vary (e.g., stuck at 0.45V) indicates a dead sensor.
Solutions:
For a CMP Sensor problem:
- Replace the CMP Sensor: This is the most likely solution. Use a quality part.
- Repair the wiring: If wires are damaged, repair them with waterproof solder and use heat-shrink tubing.
- Clean the reluctor wheel target.
For an Oxygen Sensor problem (Honda):
- Replace the faulty oxygen sensor.
- Repair any exhaust leak.
Affected Car Models
- P1395 (CMP Sensor): Very common in Hyundai, Kia, General Motors (GM), and some Ford models.
- P1395 (Oxygen Sensor): Exclusive to Honda and Acura models.
Conclusion
The P1395 code is a serious fault when related to the camshaft position sensor (CMP), potentially leaving your vehicle inoperable. For Honda/Acura owners, it indicates a less critical emissions problem but one that needs fixing to pass the emissions test.
The key to diagnosis lies in identifying the exact definition for your vehicle. Always start with a thorough visual inspection of the wiring before replacing any parts. If you are not equipped or unsure, consulting a professional mechanic is the safest solution.