The OBDII Diagnostic Trouble Code P1129 signifies a problem with the vehicle’s Manifold Absolute Pressure (MAP) Sensor signal being higher than expected. When your Pressure sensor sends a signal higher than what your ECU expects, this trouble code will be triggered.
Because your PCM / ECU does not know the true real time value of the pressure entering the engine, it cannot properly orchestrate the fuel and spark events needed to operate the motor correctly. This DTC trouble code can cause sluggish performance and poor fuel economy, and in extreme cases can render your vehicle non-startable.
We’ll be showing you how to fix the OBDII DTC P1129 in a 2000 Honda Accord 4 cylinder. This 2.3 liter F23 engine is equipped with Honda’s VTEC variable timing system, and showing you how to service an Accord MAP sensor each step along the way.
Where is my Honda MAP Sensor located?
Your Honda Accord Manifold Absolute Pressure Sensor is located on your throttle body housing, and located on top of the motor.
Because these F23 motors and most Honda motors in general are speed density or pressure driven, this sensor must work properly in order for the engine to run. This sensor is the main centerpiece to your Honda or Acura EFI system. Without this sensor input, the ECU and engine will not know how much air the motor is ingesting.
So it’s important to know how to service an Accord MAP sensor, especially if you need to pass smog.
The ECU or PCM is preprogrammed with fuel and spark values that must be referenced once the pressure value is transmitted. When incoming air enters the throttle body the sensor will read real time pressure. At idle the manifold vacuum will read higher, and as more air enters the intake manifold, the voltage to your ECU will also rise.
In order to correct your P1129 DTC OBDII trouble code, you need to test that the MAP sensor is working, and replace if needed. You will need a multimeter or similar voltage reading device to perform this test, and you may need a phillips, but we’ll save that for later.
To begin, locate your Manifold Absolute Pressure Sensor on your throttle body. This sensor is a three pin sensor that consists of a switched 5 volt power, a chassis ground and the MAP sensor signal pin.
You will be leaving the MAP sensor connected and backprobing the three pins in question and testing each with your voltmeter. Put the key into your ignition and turn it to the “ON” position to send power to all your engine’s sensors. Reference the image below for the correct Honda Accord F23 MAP sensor pinout.
The first pin we’ll be testing is the 5 volt switched power that goes to pin 1 on your MAP sensor. This is the yellow wire with a red stripe running through it. Put the black ground of your voltmeter lead to a chassis ground and backprobe this wire, you should get 5 volts of switched power here.
Next up we’ll be testing the chassis ground, which is the middle wire on your weatherproof three pin MAP sensor connector. If the sensor does not register power or ground, make sure to restore these before continuing on with our How To Service an Accord MAP sensor.
And lastly and most importantly, we’ll be testing the MAP signal wire, which is red wire shown above. This wire should transmit the pressure and vacuum values directly to your ECU.
At idle you should see a definite value between .2 and .6 volts being sent from your MAP sensor. If you do not see this value, you will want to take your phillips screwdriver and undo the two screws that hold your MAP sensor in place. With these two screws removed, you can pull off the MAP sensor while it’s still connected.
Using your voltmeter, continue to monitor your MAP signal wire while blowing air into the opening of your MAP sensor. You should see a sweeping range of voltage once you send air into the MAP sensor. There should not be any gaps or voltage jumps in this range as you are testing the operation of your MAP sensor.
If your MAP sensor is bad, you must replace it in order for your P1129 check engine light to be resolved. The part number for this unit is 37830-P0G-S00, but can also be found with the following part numbers :
HONDA OE 37830-PAA-500
HONDA OE 37830-PAA-S00
HONDA OE 37830-POG-S00
This does it for our How To Service an Accord MAP Sensor Guide and How To Service an Accord MAP Sensor and fix your DTC P1129 OBDII Check Engine Light. Let us know if you have any questions or comments by leaving them below!