Contaminated or failed MAP sensor, especially from oil or carbon fouling on the sensing element; Vacuum leak between the intake manifold and the MAP sensor, or a cracked or disconnected MAP sensor vacuum hose; Wiring fault in the MAP sensor circuit, such as an open, short, or high-resistance connection at the sensor or ECM; Failed BARO sensor, or a BARO sensor that is integrated into the MAF sensor and has drifted; Restricted intake or air filter housing causing the MAP reading to be lower than actual barometric pressure; ECM calibration issue or faulty ECM, though this is the least likely cause and should be considered only after all sensor and wiring checks pass; Engine mechanical condition such as low intake vacuum from a worn camshaft or vacuum leak that lowers MAP without a corresponding BARO change

DTC codes / GM codes / P1108

P1108 · GMBARO to MAP Sensor Comparison Too High

Q: What does code P1108 mean?

BARO to MAP Sensor Comparison Too High. P1108 on a GM vehicle means the engine control module (ECM) has compared the barometric pressure (BARO) signal against the manifold absolute pressure (MAP) signal and found the BARO reading to be excessively higher than the MAP reading when the engine is running. The ECM expects the two sensors to track within a calibrated window, and this code sets when the BARO value exceeds the MAP value by more than the allowed threshold for a calibrated time.

P1108 on a GM vehicle means the engine control module (ECM) has compared the barometric pressure (BARO) signal against the manifold absolute pressure (MAP) signal and found the BARO reading to be excessively higher than the MAP reading when the engine is running. The ECM expects the two sensors to track within a calibrated window, and this code sets when the BARO value exceeds the MAP value by more than the allowed threshold for a calibrated time.

SystemPowertrain

Code typeGM specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Malfunction indicator lamp (MIL) illuminated, often with no other symptoms besides the warning light
Rough idle or unstable engine speed at idle
Hesitation or stumble during acceleration
Poor fuel economy or rich-running exhaust smell
Elevated or erratic idle speed
In some cases, the engine may stall or run poorly at high altitude

Common causes, most likely first

Contaminated or failed MAP sensor, especially from oil or carbon fouling on the sensing element
Vacuum leak between the intake manifold and the MAP sensor, or a cracked or disconnected MAP sensor vacuum hose
Wiring fault in the MAP sensor circuit, such as an open, short, or high-resistance connection at the sensor or ECM
Failed BARO sensor, or a BARO sensor that is integrated into the MAF sensor and has drifted
Restricted intake or air filter housing causing the MAP reading to be lower than actual barometric pressure
ECM calibration issue or faulty ECM, though this is the least likely cause and should be considered only after all sensor and wiring checks pass
Engine mechanical condition such as low intake vacuum from a worn camshaft or vacuum leak that lowers MAP without a corresponding BARO change

How to diagnose and fix it

Connect a scan tool and record BARO, MAP, and key-on engine-off MAP values to confirm the fault and check whether BARO reads close to actual altitude pressure
Inspect the MAP sensor vacuum hose and intake manifold fittings for cracks, disconnection, or blockage, and repair any vacuum leak found
Check the MAP sensor wiring and connector for corrosion, pushed pins, or chafed wires, and verify reference voltage and ground at the sensor
Clean or replace the MAP sensor if it is contaminated or fails a known-good comparison test against a hand vacuum pump and multimeter
Verify the BARO sensor reading against a known barometric pressure value for your altitude, and replace the BARO sensor or MAF sensor if it is skewed
Clear the diagnostic trouble code (DTC) and perform a road test with the scan tool recording BARO and MAP to confirm the values now track within specification
If all sensors and circuits test good, check for a restricted intake or engine mechanical issue that could lower MAP, then reprogram or replace the ECM only as a last resort

Before you replace the MAP sensor

A dirty or oil-fouled MAP sensor from a leaking intake or excessive crankcase vapor is a very common cause of P1108 on GM engines, and cleaning the sensor element often restores normal operation without replacement.
The BARO sensor on many GM vehicles is integrated into the mass airflow (MAF) sensor, so a skewed MAF sensor can set P1108 even though the MAP sensor is perfectly healthy.
A vacuum leak that lowers MAP pressure at idle can trigger P1108 because the ECM sees BARO higher than MAP, so always smoke-test the intake before condemning either sensor.
Technicians sometimes replace the MAP sensor only to find the code returns because the real problem was a chafed wire in the MAP signal circuit near the intake, which is easy to miss during a visual inspection.
P1108 does not always mean a sensor has failed; a restricted air filter or collapsed intake duct can reduce MAP enough to set the code, so check the intake path before parts replacement.

Can I keep driving with P1108?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration, towing, or sustained high-speed driving because the rich or lean fueling caused by the pressure mismatch can damage the catalytic converter over time. If the engine is stalling or running very poorly, stop driving and have it towed.

Tools that help

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Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.