Testing ALDL with a volt meter
08-18-2010, 05:20 PM
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Testing ALDL with a volt meter
I am having trouble getting interface cables to connect the ecm to my laptop since upgrading to the '165 ecm from the 1985 variant. Are there pins I can check for voltage on to test whether the ecm is sending a data stream?
08-19-2010, 12:27 AM
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Re: Testing ALDL with a volt meter
Here's a picture of the ALDL connector showing the data pins:
If you test pin M with the volt meter you should get a varying voltage. I'm not sure if it will show up on a digital voltmeter though, I know when I tested mine (also a '165 ECM) on an analog meter it only showed up as a small twitch on the needle.
Don't forget that you need the 10k ohm resistor between pins A & B to get the ECM to send the 8192 baud data stream. On mine you do not need to leave the resistor in place, it can be removed after initiating the data stream.
Hope that helps.
If you test pin M with the volt meter you should get a varying voltage. I'm not sure if it will show up on a digital voltmeter though, I know when I tested mine (also a '165 ECM) on an analog meter it only showed up as a small twitch on the needle.
Don't forget that you need the 10k ohm resistor between pins A & B to get the ECM to send the 8192 baud data stream. On mine you do not need to leave the resistor in place, it can be removed after initiating the data stream.
Hope that helps.
08-19-2010, 07:02 AM
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Re: Testing ALDL with a volt meter
What BlueIroc posted, and the ALDL data stream gets wired to both pin E and M. This is done as the '7165 does both 160 and 8192 baud rates.
RBob.
RBob.
08-19-2010, 11:20 AM
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Re: Testing ALDL with a volt meter
Use of a comm port "sniffer" can help resolve connection issues too.
There are a bunch of free ones online that display the requests and responses on the serial line.
Can help see if things are wrapping or overwriting data due to timing.
There are a bunch of free ones online that display the requests and responses on the serial line.
Can help see if things are wrapping or overwriting data due to timing.
11-28-2010, 10:43 AM
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Re: Testing ALDL with a volt meter
Can you tell me more about this software. I have been trying to track down why my i cannot communicate with my ecm. what software?
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