Testing the map is the most efficient way to find out if the map is still working, or maybe the PCM is reading it wrong. Testing requires that you connect a multimeter to the MAP signal lead, then apply vacuum manually through the vacuum pump and check to see if there is any change in the reading on the MAP sensor voltage sensor.
In an event MAP sensors damaged, it would essentially be unable to react to any vacuum applied to it. If this happens, don’t worry too much. Here are clear steps on how to do it.
1). Verifies if there is power going to the MAP sensor
The first step to achieve this is to check if the sensor is being supplied with power. Note that power is in the form of 5 volts DC and is supplied to the sensor by the PCM.
After checking to see if power is reaching the sensor, the next step is to make sure it is grounded.
Please note that this can be done whether the map sensor is connected to or removed from its electrical connector.
A). Put your multimeter in DC volts mode
If you do not have a multimeter or it requires an upgrade for you, it is recommended that you use the Sino MS8268 meter.
B). Investigate the cable connecting to the pin labeled number 1, in the image viewer.
C). Place the multimeter’s black test lead on a clean metal surface on the engine or the battery’s negative pole.
D). Turn on the key but turn off the machine
The multimeter should now read 5 volts DC
Interpret results
Now that you are done with testing, the next step is to interpret what the results really mean.
If the multimeter shows 5 volts it means you are on the right track as this is the expected reading.
On the other hand, if the multimeter doesn’t read 5 volts, double check your connections and do the test again. Through this test you find out if the sensor is bad, because without 5 volts the MAP sensor cannot work.
2). Verifies if the map sensor is grounded
Checking your Honda map sensor ground circuit is pretty much the same test procedure for a 5 volt signal.
The only difference here is that you will now connect the red lead of the multimeter to the positive pole of the battery and the black lead to the MAP sensor’s ground circuit.
If the results give a positive indication that your sensor is grounded, the next step is to verify that the sensor is producing a true signal.
Remember to be very careful when performing this test. Since ground is provided directly by the PCM, care is advised not to short this cable to 12 volts of battery power or you will damage the PCM.
Here are the steps that will be asked of you:
- The multimeter should remain in volts mode and the button is on but the engine is off
- Probe the center of the sensor connector with the black multimeter lead.
- Connect the multimeter’s red lead to the positive terminal of the battery.
- The multimeter should now read 12 volts.
Interpreting results:
- If the multimeter shows 12 volts, this is the correct result to be expected.
- On the other hand, if it fails to register 12 volts, double check your multimeter connections and do the test again. If the multimeter doesn’t show 12 volts, then the MAP isn’t bad. This indicates that the problem is not caused by a MAP diagnostic trouble code.
- This is the explanation why, without a good ground path that the PCM provides internally, the map sensor won’t work.
Always be vigilant during the testing process as some mistakes can lead you to misread and lead to wrong conclusions. Make sure your cables and sensors are working optimally as this means that what you end up with is fairly accurate.
