P0108 Trouble code definition: Manifold Air Pressure (MAP) Barometric Pressure Sensor Circuit High Voltage Input Problem
When the MAP sensor sends an abnormally high voltage input to the PCM, P0108 will set and cause a check engine light. There are three wires on a MAP sensor: a 5-volt reference wire that goes from the PCM to the sensor, a ground, and a signal wire that sends information to the PCM from the sensor.
At idle, the MAP sensor should read 0.5-1 volt, and with the throttle wide open it will reach 4.5-5 volts. So when the computer gets a signal from your sensor that’s greater than 5 volts, it will cause P0108 to set.
Causes
- Most common cause is a bad MAP sensor
- Vacuum leak
- A short in the wiring either to or from the PCM
- Bad ground
- Low fuel pressure
- Engine misfiring or running rough
- Internal engine issues like a burned valve
- Faulty ECU or PCM
Symptoms
- Check engine light will illuminate
- Poor fuel economy
- Rough idle
- Erratic acceleration when driving
- Backfire due to TPS and MAP sensor not sending proper signals
How to Fix P0108
An OBD-II scanner is required to diagnose P0108 and fix the problem. You should start by clearing the code, driving the vehicle, and seeing if it comes back. Pay attention to the live data on your scanner to see if the issue is constant or intermittent.
Recommended scanner with live data: Launch CRP123 Scanner
If it’s intermittent, try to monitor the voltage and wiggle the wires while the vehicle is running. This will allow you to see if it’s a wiring issue. At this point, you should also be checking for a vacuum leak.
Try disconnecting the sensor, cleaning the connection, and reconnecting it.
Common repairs made to fix P0108
- Replacing faulty MAP sensor
- Fixing or replacing damaged wiring
- Cleaning the electrical connector and reinstalling
- If MAP sensor isn’t defective and all other causes have been investigated, then it’s time to test the ECU
