The P1105 code is a manufacturer-specific diagnostic trouble code (DTC) that typically indicates an issue with the Manifold Absolute Pressure (MAP) or Barometric Pressure (BARO) switch solenoid valve. This code is commonly found in Nissan and Infiniti vehicles, but it can also appear in other makes. When your vehicle’s Engine Control Module (ECM) detects a problem with the MAP/BARO pressure switch or its circuit, it will trigger the P1105 code and illuminate the check engine light.

P1105 Code Meaning	P1105 Code Common Causes
MAP/BARO Pressure Switch Solenoid Valve Malfunction	Faulty MAP/BARO pressure switch solenoid valve
Voltage signal from MAP/BARO pressure switch is out of range	Damaged or disconnected wiring in the MAP/BARO circuit
ECM detects an issue with the MAP/BARO system	Vacuum leaks in the intake system
Problem with the MAP sensor or its circuit	Failed or malfunctioning MAP sensor
Issue with the pressure regulation in the intake system	Clogged or restricted vacuum lines

Symptoms of P1105 Code

When your vehicle sets a P1105 code, you may experience various symptoms that can affect your driving experience. It’s essential to be aware of these signs to address the issue promptly:

1. Illuminated Check Engine Light: The most common and obvious symptom is the check engine light turning on.
2. Poor Engine Performance: You might notice a decrease in engine power, especially during acceleration or when climbing hills.
3. Rough Idle: The engine may run roughly or unevenly when idling, sometimes accompanied by vibrations.
4. Reduced Fuel Efficiency: As the engine management system struggles to maintain proper air-fuel ratios, you may see a drop in fuel economy.
5. Stalling or Hesitation: In some cases, the engine might stall or hesitate during acceleration or when coming to a stop.
6. Hard Starting: You may experience difficulty starting the engine, particularly when it’s cold.
7. Inconsistent Engine Speed: The engine RPMs might fluctuate unexpectedly, even when maintaining a steady speed.
8. Increased Emissions: Although not immediately noticeable, the vehicle may produce higher levels of emissions due to improper fuel mixture.

Technical Explanation of the P1105 Code

To understand the P1105 code better, it’s crucial to know how the MAP/BARO system works in your vehicle:

The Manifold Absolute Pressure (MAP) sensor measures the pressure inside the intake manifold, which helps the Engine Control Module (ECM) determine the engine load. This information is crucial for calculating the correct air-fuel mixture and ignition timing.

The Barometric (BARO) pressure sensor, which is often integrated with the MAP sensor in modern vehicles, measures atmospheric pressure. This data helps the ECM adjust for changes in altitude and weather conditions that affect air density.

The MAP/BARO pressure switch solenoid valve is responsible for switching the airflow passage based on signals from the ECM. It allows the system to alternate between measuring manifold pressure and atmospheric pressure as needed.

When the ECM detects that the voltage signal from the MAP/BARO pressure switch is outside the expected range, it sets the P1105 code. This could be due to a problem with the solenoid valve itself, issues with the electrical circuit, or problems with the sensors providing incorrect data.

Step-by-Step Diagnosis of P1105 Code

To diagnose the P1105 code effectively, follow these steps:

1. Verify the code: Use an OBD-II scanner to confirm the P1105 code and check for any additional codes that might be present.
2. Visual inspection:

1. Check all vacuum lines connected to the MAP sensor and intake manifold for leaks, cracks, or disconnections.
2. Inspect the electrical connectors and wiring harness for the MAP sensor and MAP/BARO pressure switch solenoid valve for damage or corrosion.
3. Look for any signs of damage to the intake manifold or nearby components.
4. Test the MAP/BARO pressure switch solenoid valve:

1. Locate the solenoid valve, typically near the firewall or on the intake manifold.
2. With the engine off, disconnect the electrical connector from the solenoid.
3. Use a multimeter to measure the resistance across the solenoid terminals. Compare the reading to the manufacturer’s specifications.
4. Apply 12 volts to the solenoid and listen for an audible click, indicating it’s functioning.
5. Check the MAP sensor:

1. Locate the MAP sensor, usually on or near the intake manifold.
2. With the key on but the engine off, use a voltmeter to measure the sensor’s output voltage.
3. Start the engine and observe the voltage change. It should vary smoothly as you rev the engine.
4. Compare your readings to the manufacturer’s specifications.
5. Inspect the wiring:

1. Check the continuity of the wires between the ECM and the MAP/BARO pressure switch solenoid valve.
2. Look for any signs of shorts, open circuits, or high resistance in the wiring.
3. Perform a smoke test:
4. Use a smoke machine to pressurize the intake system and check for any leaks that might affect MAP sensor readings.
5. Check ECM grounds:
6. Ensure all ECM ground connections are clean, tight, and free of corrosion.
7. Use advanced diagnostic tools:
8. If available, use a oscilloscope to observe the MAP sensor signal and look for any abnormalities.

Solutions for P1105 Code

Based on your diagnosis, here are potential solutions for the P1105 code:

1. Replace the MAP/BARO pressure switch solenoid valve:
   If the solenoid fails the resistance test or doesn’t click when powered, it needs replacement. Ensure you get the correct part for your specific vehicle model.
2. Repair or replace wiring:
   If you find damaged, corroded, or open circuits in the wiring harness, repair or replace the affected sections. Always use the correct gauge wire and proper connectors.
3. Replace the MAP sensor:
   If the MAP sensor is providing incorrect readings or has failed, replace it with a new unit. Make sure to use an OEM or high-quality aftermarket sensor.
4. Fix vacuum leaks:
   Repair any vacuum leaks found during the smoke test. This may involve replacing cracked vacuum lines, tightening connections, or repairing the intake manifold if necessary.
5. Clean or replace electrical connectors:
   If you find corrosion on the electrical connectors, clean them thoroughly. If cleaning doesn’t resolve the issue, replace the connectors.
6. Update ECM software:
   In some cases, a software update for the Engine Control Module may resolve issues with sensor interpretation or solenoid control.
7. Replace the ECM:
   In rare cases where all other components check out, the issue may lie within the ECM itself. This should be considered a last resort and only done after thorough testing.

Cost Estimates for P1105 Code Repairs

The cost to fix a P1105 code can vary widely depending on the root cause and your vehicle’s make and model. Here are some rough estimates:

• MAP/BARO pressure switch solenoid valve replacement: $100 – $300
• MAP sensor replacement: $50 – $200
• Wiring repair: $50 – $300 (depending on the extent of damage)
• Vacuum leak repair: $50 – $500 (depending on the location and severity of the leak)
• ECM software update: $50 – $200
• ECM replacement: $500 – $2000 (this is a worst-case scenario)

These estimates include parts and labor. DIY repairs can significantly reduce costs, but ensure you have the necessary skills and tools before attempting repairs.

Warnings and Recommendations

Warning: Ignoring the P1105 code can lead to decreased engine performance, reduced fuel efficiency, and potential damage to other engine components over time.

Here are some important recommendations:

1. Always use high-quality replacement parts to ensure longevity and proper function.
2. If you’re not comfortable with automotive diagnostics and repairs, seek help from a qualified mechanic.
3. After repairs, clear the code and test drive the vehicle to ensure the problem is resolved.
4. Regular maintenance, including timely replacement of air and fuel filters, can help prevent issues that may trigger the P1105 code.
5. When replacing sensors or solenoids, be careful not to damage nearby components or overtighten fittings.
6. If you live in an area with extreme temperatures or high altitude, be aware that these conditions can affect MAP sensor readings and may require additional calibration.
7. Keep records of all repairs and diagnostic procedures for future reference.

In conclusion, the P1105 code, while specific to certain manufacturers, is a manageable issue when approached systematically. By following the diagnostic steps outlined above and implementing the appropriate repairs, you can resolve this problem and restore your vehicle’s performance. Remember, if you’re ever in doubt about your ability to diagnose or repair the issue safely, it’s always best to consult with a professional mechanic.

Frequently Asked Questions About P1105 Code

• Can I drive my car with the P1105 code?
  While you may be able to drive short distances, it’s not recommended. The code indicates a problem that can affect engine performance and fuel efficiency.
• How urgent is it to fix a P1105 code?
  It’s important to address this code promptly. Ignoring it can lead to decreased performance, poor fuel economy, and potential damage to other engine components over time.
• Will the P1105 code clear itself?
  The code may clear temporarily if the issue resolves, but it will likely return if the underlying problem isn’t fixed. Proper diagnosis and repair are necessary for a permanent solution.
• Can a vacuum leak cause the P1105 code?
  Yes, vacuum leaks can cause inaccurate MAP sensor readings, potentially triggering the P1105 code. A thorough inspection of the intake system is crucial during diagnosis.
• How often should I replace my MAP sensor?
  MAP sensors don’t have a specific replacement interval. They typically last the lifetime of the vehicle but can fail due to contamination or electrical issues.
• Can a bad oxygen sensor cause a P1105 code?
  While not directly related, a faulty oxygen sensor can cause the ECM to misinterpret engine conditions, potentially affecting MAP sensor readings and triggering related codes.
• Is the P1105 code covered under warranty?
  Coverage depends on your vehicle’s age, mileage, and specific warranty terms. Check your warranty documentation or consult with your dealer for information.
• Can extreme weather conditions trigger a P1105 code?
  Extreme temperatures or rapid altitude changes can affect MAP sensor readings. However, a properly functioning system should adapt to these conditions without triggering codes.