TEST 3: Verifying The Ground Circuit
So far, your MAP sensor diagnostic has confirmed two things:
- One: The MAP sensor is not producing a decreasing/increasing MAP voltage signal as you apply/release vacuum to it.
- Two: The MAP sensor is getting fed with power (in the form of 5 Volts DC).
The next step, and the last one, to confirm that it's bad is to make sure it's getting Ground.
A word of caution: Since this circuit is directly connected to the PCM, be very careful and don't short this wire to battery power (12 Volts), or you WILL FRY the PCM.
Alright, this is what you'll need to do:
- 1
Disconnect the MAP sensor from its connector.
- 2
Connect the red multimeter test lead on the battery's positive (+) post.
- 3
Set your multimeter to Volts DC mode.
- 4
Turn the key to the ON position (but engine OFF).
- 5
Probe the front of the terminal that connects to the wire labeled with the number 2 with the black multimeter test lead.
- 6
Your multimeter should register 10 to 12 Volts DC.
OK, let's take a look at what your results mean:
CASE 1: The multimeter registered 10 to 12 Volts. This is the normal result.
This also means that the MAP sensor is fried and needs to be replaced if you have confirmed:
- The MAP sensor is not producing the correct values when you applied vacuum (TEST 1).
- The MAP sensor does have power (TEST 2).
- In this test step you have confirmed that the MAP sensor does have a solid path to Ground.
CASE 2: The multimeter DID NOT register 10 to 12 Volts. Double check your multimeter connections and repeat the test.
If your multimeter results still do not indicate 10 to 12 Volts, then the MAP sensor is not fried and not the cause of the MAP diagnostic trouble code (DTC) issue.
Here's why: Without a good path to Ground, that the PCM provides internally, the MAP sensor will not work. With this test result, you have eliminated the MAP sensor as bad.
MAP Sensor Code Won't Go Away
Quite a few things can fool the PCM, on your Chrysler/Dodge mini-van, into thinking that the MAP sensor is bad when it isn't.
If you have already tested and/or replaced the MAP sensor but the trouble code keeps coming back (after erasing it and road testing the mini-van), then these suggestions might inspire your next diagnostic move:
- O-Ring failure: The MAP sensor's O-rings, the ones located on its vacuum inlet port are missing or are too old and they're not sealing properly. Visually check the O-rings and replace if necessary.
- Engine compression issue: The engine has several cylinders with very low engine compression causing it to idle rough and thus producing low or erratic vacuum. For this I suggest a compression test.
- Intermittent MAP sensor failure: The MAP sensor is failing intermittently. Which means that it works fine most of the time, but every now and then it doesn't:
- I have found that the best way to test these intermittent problems, is to slightly tap the MAP sensor with the handle of a screw-driver and see if this tapping screws up the voltage readings as I apply vacuum.
- Damaged connector: The MAP sensor's connector is bad, usually the locking tab is broken and the connector has worked itself loose, causing an intermittent false connection.
- Fuel pump failing: Your fuel pump is starting to go bad and is not sending enough fuel and/or fuel pressure up to the fuel injectors. I suggest a fuel pump test.
- EGR stuck open: The EGR valve is stuck open (on EGR valve equipped vehicles).
More 3.3L Chrysler, Dodge, And Plymouth Mini-Van Tutorials
You can find a complete list of tutorials in this index:
Here's a sample of the tutorials you'll find in the index:
- How To Test The MAP Sensor (2001-2004 3.3L V6 Chrysler And Dodge Mini-Van).
- How To Test The Alternator (2001-2007 3.3L Chrysler).
- How To Test Engine Compression (1991-2007 3.3L V6 Chrysler, Dodge, Plymouth Mini-Van).
- How To Test The Coil Pack 3.3L, 3.8L Chrysler, Dodge, Plymouth (at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!
