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paulrice
User
May 5, 2012, 2:08 PM
Post #1 of 11
(2018 views)
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2001 nissan altima 129000 miles check engine light on when we go to read the code we cant it says check connections went to two places same thing and i checked it also same thing seams like it is not communcating with the computer? car runs fine
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nickwarner
Veteran
/ Moderator
May 5, 2012, 2:51 PM
Post #2 of 11
(2001 views)
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Check all the fuses. You have to have 12v at the terminal of the DLC for communication to be possible. Many times a circuit for an accessory like the cigarette lighter is fused with it. Blow the fuse and you have no communication. You will need to solve the communication problem before we can resolve the code issue obviously. If you need some more help to get this to work let us know.
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paulrice
User
May 5, 2012, 4:47 PM
Post #3 of 11
(1974 views)
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checked have 12volts constant at one of the connectors all fuses are good
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Discretesignals
Ultimate Carjunky
/ Moderator
May 5, 2012, 5:25 PM
Post #4 of 11
(1964 views)
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Check pin 16 of the data link connector for battery voltage.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on May 5, 2012, 5:28 PM)
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paulrice
User
May 6, 2012, 7:52 AM
Post #5 of 11
(1942 views)
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have 12voltson pin #16
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Discretesignals
Ultimate Carjunky
/ Moderator
May 6, 2012, 8:35 AM
Post #6 of 11
(1937 views)
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Make sure PIN 8 has battery voltage with ignition on.
Make sure PIN 5 has a good ground to battery negative.
Inspect the diagnostic connector wiring on the back of the connector. Make sure you don't have any broken or damaged wires.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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paulrice
User
May 6, 2012, 10:31 AM
Post #7 of 11
(1924 views)
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have good ground on #5 have 12volts with key on on #8 wires seem fine in back of connector?
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Discretesignals
Ultimate Carjunky
/ Moderator
May 6, 2012, 11:56 AM
Post #8 of 11
(1916 views)
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Just curious, but which places did you go to have codes read?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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paulrice
User
May 6, 2012, 12:05 PM
Post #9 of 11
(1910 views)
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I have a code reader and i went to advance auto parts store
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Discretesignals
Ultimate Carjunky
/ Moderator
May 6, 2012, 12:31 PM
Post #10 of 11
(1905 views)
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Should be able to communicate with the ECM with a generic code reader. Might have to take it to a shop to see if their enhanced scan tool can access the ECM.
I haven't seen very many data link failures with the ECU still operational. There is very limited service information on how to troubleshoot a data link problem. There are 3 circuits that deal with the data transmission. PIN 7 is K LINE and PIN 13 is SCIRX. These two circuits will have between 0-14 volts depending on the data transfer with the scan tool connected. PIN 12 SCITX and will have between 3-9 volts. You really need an oscilloscope to monitor the data transmission by back probing the connector at the ECM. I don't have any clue as to what this waveform should look like, but it is going to be a digital square wave signal and very fast.
If you can't get into the ECM with an enhanced scan tool on the OEM or generic side, your circuits to and from the datalink connector and ECM aren't shorted or open, and you have good power and ground to the ECM, you might have an internal problem in the ECM itself.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on May 6, 2012, 12:32 PM)
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paulrice
User
May 6, 2012, 12:38 PM
Post #11 of 11
(1900 views)
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where is the ecm located?
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