DTC P0109 – MAP Sensor Circuit High Voltage

DTC P0109 – MAP Sensor Circuit High Voltage


The OBDII Trouble Code P0108 has to do with your car’s Manifold Absolute Pressure (MAP) Sensor giving your ECU incorrect data, or more accurately too high of a voltage value that your ECU is used to. This can cause your car to go into limp mode, which will allow you to get the vehicle to help or an experienced mechanic who can troubleshoot your issue further.

To troubleshoot the circuit high issue, we’ll be looking at a 2003 Acura RSX Type S that is showing this code after the owner tried some Seafoam to clean the motor. As you will need to reference the data or circuit values in the ECU / PCM, you will want a datalogger or similar type scan tool.


  • Tip : Before ordering a replacement MAP Sensor, you will want to check the following steps to ensure that something else isn’t causing your OBDII code.
  • Check MAP Connector – Make sure the MAP sensor is connected and that there is no break or corrosion preventing contact.
  • Check Voltage and Alternator – Ensure your vehicle’s voltage is correct.
  • Check all Engine Grounds – As differences in the ground can cause spikes or lulls in voltage, recheck your vehicle’s grounds to make sure this isnt the problem

We’ll be taking a look at this trouble code in a 2003 Acura RSX Type S, and showing you how to fix your ODBII error code by testing your 37830-PGK-A01, MAP Sensor.


This sensor is connected by a 3 prong weather proof connector and is located on side of your throttle body assembly, to the right of your engine if you are looking from the front of the RSX.
Other OBDII codes that may be stored in your ECU could include DTC P1129 : MAP Sensor Signal Higher Than Expected.
To begin start your engine and hold engine speed ( RPM ) to 3000 until your radiator fans kick on and your engine has reached operating temperatures. You will now use your scan tool or datalogger to read the raw values provided to your ECU by your MAP Sensor.
The operating ranges you are looking for are values above 101kPa ( 760mmHg, 30in Hg ) or in voltage, you are looking for a value greater than 2.8V. If the value you see is lower than the values listed, your issue may be intermittent. Clear your DTC codes and try to replicate the conditions in which your DTC code first appeared.
If your values are greater turn off your engine, disconnect the 3 pin Manifold Absolute Pressure Sensor and jump Pin 2 and Pin 3 using a jumper wire. 
Now go back to your scan tool and take a look at your raw MAP values, with the same ranges as we tested with before. You are looking for values greater than 101kPa ( 760mmHg, 30in Hg ) or 2.8V. 
By jumping pin 2 and pin 3 you should definitely see values higher than those numbers. If your MAP sensor is still giving you values below this threshold, you need a replacement MAP sensor : 37830-PGK-A01, MAP Sensor.
If the values are higher, unplug your jumper now and grab your voltmeter and test the voltage between pin 1 and pin 3. Pin 1 is VCC1 a combination yellow/red wire and Pin 3 is SG1 a combination green/white wire.
Voltage here should be roughly 5 volts, if the voltage you read between these 2 pins is not 5 volts you need to replace pin 11 on the A connector of your ECU/PCM, as this wire may have a short in it.
If your voltage at the MAP sensor checks out, it’s time to check at your ECU/PCM. 
To test your Honda MAP sensor, unplug the 31 pin ECU connector “A” and using a jumper wire connect the MAP input ( Pin 19 ) and the SG1 pin which is Pin 11. You are going to be checking for values again, so plug in your datalogger and take a look at the values the ECU is reading now that the jumper wire is there. 
If your values are still lower than 101kPa ( 760mmHg, 30in Hg ) or 2.8V, then there is an issue with the wire between your PCM/ECU and the MAP sensor. The wire you will want to replace is A19 on your 31 pin A connector.
If the values are higher than the specifications provided, your ECU has failed or needs an update, either replace it or take it to Honda for service.
Happy Driving!