TEST 1: Checking The MAP Sensor Output
To get our MAP sensor diagnostic on the way, the first thing we need to do is check the output of the MAP sensor, using a scan tool (with Live Data capability).
If the MAP sensor has failed; we'll be able to see the wrong pressure value it's reporting on the scan tool display.
This a very easy and simple test and I'll show you how to do it.
In case you don't have a scan tool with Live Data capability, check out my recommendation: Actron CP9580 Scan Tool Review
This is what you need to do:
Connect your scan tool to the OBD II connector and turn the key to the ON position.
Once your scan tool powers on, go to its Live Data mode and scroll down to the MAP PID (Parameter Identification). See the photo in the image viewer above.
NOTE: Don't start the engine. This test is done with the Key On Engine Off (KOEO).
Take a look at what the MAP sensor PID is registering.
What is your scan tool showing for the MAP sensor value?
The MAP PID should register 29 "HG (± 1 "HG) on your scan tool.
NOTE: "HG stands for inches of mercury.
Let's take a look at what your test results mean:
CASE 1: The MAP sensor PID showed the indicated value. This tells you that the MAP sensor is OK at this time and that the problem is intermittent.
I'll explain: If the problem with the MAP sensor, and which is causing the P0107 Manifold Absolute Pressure (MAP) Circuit Low Voltage diagnostic trouble code (DTC), were present... you would have seen any other value but 29 "HG (± 1 "HG) on your scan tool.
If the P0107 DTC won't go away or keeps coming back, take a look at this subheading: MAP Sensor Is Good But Code Doesn't Go Away! for further testing tips/suggestions.
CASE 2: The MAP sensor PID DID NOT show the indicated value. This test result indicates a bad MAP sensor or a fault in the sensor's circuit. Why? Because with the Key On Engine Off (KOEO), the MAP sensor should only be measuring the ambient (outside) air pressure (known as barometric pressure).
Unless your car is parked on the summit of Mount Everest in the Himalayas... the pressure of the outside air is usually 29 "HG (± 1 "HG). So, when the scan tool indicates a big deviation from this number... it's usually due to a bad MAP sensor.
The next step is go to: TEST 2: Verifying The MAP Sensor Has Power.
TEST 2: Verifying The MAP Sensor Has Power
The MAP sensor, like any other electrical/electronic device on your Honda, needs power and Ground to work.
So, in this test step, we're gonna' make sure the MAP sensor is getting power.
We'll be using a multimeter to test for this power since it comes in the form of 5 Volts DC (and provided by PCM directly).
NOTE: This test can be done with the MAP sensor connected or disconnected to its electrical connector.
Alright, this is what you'll need to do:
Place your multimeter in Volts DC mode.
If you don't have a multimeter or need to upgrade yours, check out my recommendation here: Abe's multimeter Recommendation (at: easyautodiagnostics.com).
Probe the wire that connects to the pin labeled with the number 1, in the image viewer, with the red multimeter test lead.
NOTE: Do not probe the front of the connector with the multimeter's test lead or you'll damage the connector's metal terminal. You should back-probe the connector or use a wire-piercing probe on the wire.
Ground the multimeter's black test lead on a clean and unpainted metal surface on the engine or better yet, on the battery's negative post.
Turn the Key On (but engine off).
Your multimeter should show you 5 Volts DC.
OK, now that the testing part is done, let's take a look at what your results mean:
CASE 1: The multimeter registered 5 Volts. This is the correct result. The next step is to check that the MAP sensor is getting Ground. For the Ground test, go to: TEST 3: Verifying The MAP Sensor Has Ground.
CASE 2: The multimeter DID NOT register 5 Volts. This results lets you know that the MAP sensor is not bad, since without these 5 Volts DC, the MAP sensor can not function.
Although it's beyond the scope of this article to troubleshoot the cause of these missing 5 Volts, you have now eliminated the MAP sensor as bad. Resolving the issue that is keeping these 5 Volts from being supplied will solve the MAP sensor issue on your Honda vehicle.