P0108 medium Severity

P0108: Manifold Absolute Pressure/Barometric Pressure Circuit High Input

May cause rough idling, poor engine performance, decreased fuel economy, and potential stalling; driving with the fault present is not recommended.

Overview

P0108 indicates a high voltage input from the MAP or BARO sensor circuit, suggesting MAP/BARO sensor malfunction, wiring issues, vacuum leaks, or ECM interpretation errors affecting air pressure readings.

Common Symptoms

  • Check Engine Light (MIL) illuminated
  • Rough idling or unstable engine operation
  • Decreased fuel economy
  • Engine hesitation or reduced performance

Most Common Causes

Faulty MAP sensor or BARO sensor high

Internal sensor failure can send unusually high voltage signals that trigger the code.

Wiring harness issues (short, open, corrosion) high

Frayed wires or poor connections in the sensor circuit often lead to high voltage readings.

Vacuum leaks in intake manifold or hoses medium

Vacuum leaks can skew true manifold pressure, causing incorrect high signal from the MAP sensor.

ECM misinterpretation or fault low

Rare cases involve ECM software/hardware errors causing incorrect interpretation of sensor voltage.

Diagnostic Steps

  1. Connect OBD-II scanner and verify P0108 and any related codes.
    Expected: P0108 code stored; check for other air intake or MAP-related codes.
    Interpretation: Confirms MAP/BARO circuit high input condition.
  2. Visually inspect MAP/BARO sensor wiring and connectors for damage, corrosion, or loose terminals.
    Expected: No visible damage or corrosion; secure connectors.
    Interpretation: Damaged wiring may cause high signal or short to voltage.
  3. Measure MAP sensor output voltage with engine off and key on; compare to barometric pressure reading.
    Expected: Sensor voltage should match barometric pressure reading within specification.
    Interpretation: Voltage discrepancy suggests sensor malfunction.
  4. Start engine and monitor MAP sensor voltage at idle and with load.
    Expected: Voltage should drop at idle and vary with load.
    Interpretation: Static high voltage indicates sensor or circuit issue.
  5. Inspect intake manifold and vacuum lines for leaks using smoke test or visual inspection.
    Expected: No leaks detected; intact vacuum lines.
    Interpretation: Leaks can produce abnormal pressure readings.

Repair Solutions

Replace faulty MAP/BARO sensor easy
Estimated Cost: $50 - $200

Sensor cost varies by vehicle; replacement often resolves code when sensor is defective.

Repair or replace damaged wiring/connectors medium
Estimated Cost: $50 - $300

Addressing shorts, opens, or corrosion in the harness prevents erroneous signals.

Fix vacuum leaks (intake manifold gasket, hoses) medium
Estimated Cost: $100 - $400

Proper sealing of intake system ensures accurate MAP sensor readings.

ECM update or replacement (rare) hard
Estimated Cost: $300 - $1000

Consider only when sensor and wiring are verified good and code persists.

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Replacing MAP sensor without checking vacuum leaks or wiring
  • Assuming code indicates lean condition instead of high signal issue
  • Misattributing symptoms to mass airflow sensor problems

Frequently Asked Questions

What is the definition of the P0108 engine code?

Technically, the P0108 code represents Manifold Absolute Pressure/Barometric Pressure Circuit High Input. It usually points to a fault within the Air Intake.

Is it safe to drive with a P0108 code?

The P0108 code is considered medium severity. May cause rough idling, poor engine performance, decreased fuel economy, and potential stalling; driving with the fault present is not recommended.

What happens when the P0108 code is active?

You may experience the following: Check Engine Light (MIL) illuminated, Rough idling or unstable engine operation, Decreased fuel economy.

What causes the P0108 code?

Potential culprits include: Faulty MAP sensor or BARO sensor, Wiring harness issues (short, open, corrosion), Vacuum leaks in intake manifold or hoses. A proper diagnosis is recommended.

What is the price difference for fixing P0108?

The cost varies significantly based on the root cause. For example, replacing a Replace faulty MAP/BARO sensor typically costs between $50 and $200, while fixing a ECM update or replacement (rare) can range from $300 to $1000.

Does P0108 affect Ford, Toyota, or Honda?

The P0108 code is a generic powertrain code, meaning it applies to almost all makes and models, such as Honda, Toyota, VW, Ford, and Chevy.

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