Fix P0105: Mechanic’s Solutions That WORKED!

The OBD2 code P0105 means there’s a problem with the MAP sensor circuit, which helps the car’s computer figure out how much air is going into the engine. If this sensor isn’t working right, the engine might not run as well as it should. This can affect how the car drives and how much gas it uses.

P0105 quick overview

Meaning	P0105: Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction
Is it serious?	Yes, it can cause engine and driving problems.
Possible causes	– Bad MAP sensor – Wiring problems – Vacuum leaks
How to diagnose?	Check the MAP sensor for damage or dirt. Look at the wires connected to the sensor for any breaks or loose connections. Test for vacuum leaks in the system that might mess with the sensor’s readings

How to fix P0105 – learn from mechanics

I looked into P0105 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Jaguar P0105

Vehicle Information 2004 Jaguar XJ8 4.2L

Issue + Repair History

• Recurring OBD2 trouble codes: P0105 (MAP barometric pressure circuit malfunction) and P0442 (evap leak – small).
• Previous attempts to resolve included smoke checking the MAP system and evap system for leaks, and replacing the MAP sensor, purge valve, and EGR valve. However, both codes persist.
• Car runs with no discernible issues; no rough idling or surging observed.

Other OBD2 Codes + Test Results

• No additional OBD2 codes detected.
• No abnormalities observed during system checks and smoke tests for leaks.

Mechanic Suggestions

• Inspect gas tank seals and storage canister for evap system leaks, especially considering the persistent P0442 code.
• Consider performing induction/injector service to improve fuel trim strategy and monitor fuel trim strategy during subsequent drives.
• Check if the vehicle has had the JOO4 recall completed, which involves ECM/TCM updates and addresses issues related to fault P0105. Perform necessary updates if not completed.
• If fault P0105 persists after updates, follow Jaguar’s SSM recommendations, including cleaning the engine cylinders with a top-end cleaner, using BG Air Intake System Cleaner, and clearing DTCs after the cleaning process.

Final Fix

• Updated the engine control unit as recommended for fault P0105.
• Identified a faulty gas cap for the P0442 code and replaced it, resolving the evap issue.

Case #2: Subaru P0105

Vehicle Information 1995 Subaru Legacy 2.2L

Issue + Repair History

• Persistent MIL (Malfunction Indicator Lamp) illuminated.
• OBD2 trouble code P0105 retrieved using a Snap-On 2500 Scanner, which is unusual for a vehicle equipped with a Mass Airflow Sensor.
• Constant TCS OFF light illuminated, potentially indicating a separate issue.
• Repair history from the dealer was not disclosed.

Other OBD2 Codes + Test Results

• No additional OBD2 codes mentioned.

Mechanic Suggestions

• Suspect erroneous information from the reader or potentially incompatible software cartridge causing the retrieval of incorrect codes.
• Consider using a different data scanner for further diagnosis to confirm the code.
• Investigate the connection between the constant TCS OFF light and the MIL.

Final Fix

• Determined that the reader was displaying erroneous information.
• Used another data scanner, which pointed to the EGR Sensor.
• Replaced the EGR sensor, resolving the problem associated with the MIL.

Case #3: Nissan P0105

Vehicle Information 1996 Nissan Maxima SE 3.0L

Issue + Repair History

• Intake manifold was removed to replace the knock sensor, resulting in a knock sensor code.
• Noticed a blocked EGR port during the intake manifold removal, which was cleaned.
• Now encountering OBD2 trouble code P0105 after reassembly.
• Verified battery voltage at the red wire and 0.3V at each of the other wires on the MAF connector.
• MAF voltage readings observed:
  • Before starting vehicle: 0.20V
  • Start vehicle cold: 1.50V
  • Idle at 900rpm: 1.20V
  • At 2000RPM: 1.83V
  • Snap throttle: 3.59V
• Attempted using another known good MAF sensor with similar results.
• Code would not clear despite troubleshooting efforts.

Other OBD2 Codes + Test Results

• No additional OBD2 codes mentioned.
• Manifold vacuum readings:
  • Idle: 20 in.
  • Cruise: 23 in.

Mechanic Suggestions

• Perform a drive cycle to clear the DTC (Diagnostic Trouble Code).
• Check for vacuum line reattachment on the throttle chamber firewall side, as it might not have been properly reattached during reassembly.
• Test the absolute pressure sensor as per the procedures outlined in Mitchell Ondemand5.

Final Fix

• Performed a drive cycle as recommended
• Drove the car approximately 100 miles, rescanned, and found that the P0105 code was no longer present, indicating a successful resolution of the issue.

Diagnostic Step	Brief Explanation
Inspect the MAP Sensor	Look at the sensor for any signs of dirt or damage that could interfere with its operation.
Examine Wiring and Connections	Check the electrical connections to the MAP sensor for breaks, wear, or disconnections.
Search for Vacuum Leaks	Use tools or listen for leaks in the system that might affect the sensor’s accuracy.