P0108
Manifold Absolute Pressure/Barometric Pressure Circuit High Input
If your code reader dashboard displays the generic DTC error code P0108, your vehicle is currently experiencing an active failure related to "Manifold Absolute Pressure/Barometric Pressure Circuit High Input". Proper system troubleshooting is required to safely clear this warning.
Driver's Summary
P0108 is triggered when the PCM detects an abnormal condition associated with manifold absolute pressure/barometric pressure circuit high input. Drivers typically experience engine surging, rich exhaust smell, poor acceleration when this code is active. You can typically drive short distances, but ignoring this code long-term will cause accelerated component wear and higher repair costs.
Symptoms
Engine surging, rich exhaust smell, poor acceleration
Common Causes
- Faulty MAP sensor
- Short to battery voltage in MAP circuit
- Failed fuel pressure regulator causing high pressure
- Bad PCM
How to Fix
- 1 Test and replace MAP sensor
- 2 Inspect wiring harness for shorts
- 3 Test fuel system pressure
- 4 Reflash or replace PCM
Technical Explanation
Detection of P0108 occurs when the ECM cross-references multiple sensor inputs and determines that the reported values are physically inconsistent or out-of-range. Sensor output is cross-validated against complementary sensor data (such as MAF vs. MAP correlation, or upstream vs. downstream O2 comparison) to confirm the fault is genuine and not a result of a sensor reading an actual engine condition. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
Is It Safe to Drive?
Code P0108 allows for cautious short-distance driving, but the underlying cause — most likely faulty map sensor — will worsen with time. Fuel economy suffers, and ignoring the fault for weeks can turn a $80 fix into a much larger repair bill.
Mechanic's Pro Tip
The most common mistake with P0108 is replacing the sensor without verifying the reference voltage and ground integrity first. Use a scan tool to monitor the sensor's live output; a truly failed sensor shows a stuck, flatlined reading — a sensor that fluctuates but reads slightly off usually indicates a wiring or vacuum issue, not a dead sensor. Always spray electrical contact cleaner on the connector pins before condemning the sensor.
MAP sensor: $80 - $200; Labor: $100