Wiring harness problem? (Not on my Chevelle.)

1293 Views 6 Replies 4 Participants Last post by chevguy, Dec 5, 2005

chevguy

Discussion Starter · Dec 3, 2005

First off, I’m sorry to have to post a non-Chevelle question here but I’m out of other options. I have a 97 Dodge Avenger that is throwing a misfire code. I’ve changed the plugs, wires, cap, rotor, and the Intake Air Temperature sensor. When none of those resolved my problem I ran some tests on the MAP sensor. I followed the instructions in my Chilton book to do them. The instructions are as follows:

On the Sensor Connector
Terminal 1 is the 5-volt power supply
Terminal 2 is the Sensor Ground
Terminal 3 is the Map Sensor Signal

On the PCM plug
Terminal 36 is the MAP Sensor signal
Terminal 43 is the sensor ground
Terminal 61 is the 5-Volt power supply

1. check connector, etc.

2. Test the MAP sensor output voltage at the sensor connector between terminals 1 and 3.

3. With the ignition switch ON and the engine not running, the output voltage should be 4-5 volts. The voltage should fall to 1.5 - 2.1 volts with a hot, neutral idle speed condition. If OK, go to step 4 or 5. If not OK, go to Step 6 or 7.
when I tested the connector, my voltmeter read zero. When I dropped the meter down to the lower range (2V), my output is about .003

6. Test the MAP sensor ground circuit at the sensor connector terminal 1 and PCM terminal 43. If OK, go to Step 8. If not OK, repair as necessary.
this test comes out fine

7. This test is for a 95 only.

8. Test the MAP sensor supply voltage between the sensor connector terminals 2 and 1 with the ignition key in the ON position. The voltage should be about 4.5 - 5.5 volts.
This tests out fine

9. There should also be 4.5 - 5.5 volts at terminal 61 of the PCM.
This tests out fine

10. This test is for a 95 only.

11. If not, repair or replace the wire harness as required.

So as far as I can tell, the only problem that I found was a problem way up at step 3. Now, if my understanding is correct, the meter should be testing the circuit completeness between the supply and the signal on the PCM side. However, this still doesn’t make perfect sense to me how this can be a complete circuit. So, does this sound like a wiring problem? If so, how can this be fixed? Do I need to replace the entire harness? Any other suggestions?

Thanks for any help that you may be able to provide.

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vrooom3440

· #2 · Dec 3, 2005

I would wonder about the procedure... usually electrical circuit voltages are measured with respect to ground. Sounds like the got the wrong terminal. It would be a good procedure to test the map sensor to measure the signal against ground. Even better if they gave you vacuum numbers to correlate to the voltage numbers rather than the goofy ranges to allow for ranges of vacuum.

Just a question: are you doing this test with the connector in the MAP sensor or out of it? It needs to be tested with the connecter plugged in.

I would also expect that you should be able to get a better resolution than a generic "misfire" from the EFI computer.

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vrooom3440

· #5 · Dec 4, 2005

chevguy said:
I'm doing the test without the connecter plugged into the sensor (although I'm attempting as we speak to find a way to conect the sensor and the sensor connector and still be able to test it.

I actually get codes for mis-fires on cylinders 1 and 6.

This will not give you a valid result as the sensor output is "floating" at that point and not really connected to anything. You will need to measure the voltages with everything plugged in.

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