Ecu resistor open circuit?
Thread Starter
Staging Lane
Joined: Apr 2023
Posts: 69
Likes: 7
From: Tx
Ecu resistor open circuit? having comm issues when scanning and reading vehicle with a obd2 scanner and with hpt editor, checked resistance from pin 6 and 14 on obd it reads at 80ish an slowly climbs up to 120ohm, i started unplugging things and noticed whenever i unplug my ecu and go check ohms there is no slowly climbing up to 120 it instantly reads 120ohms, is it unrealistic for me to just buy a new ecu or is there some more tests i should preform that i havent
Moderator
Joined: Aug 2010
Posts: 7,323
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From: Ann Arbor, MI
It sounds like your Ohm meter is simply charging a capacitor in the ECU; seems like very normal behavior. Pins 6 and 14 are the CAN bus high and low signal lines which go to places other than the ECU.
I don't know if your measured 80 or 120 Ohms is typical. CAN bus voltage is 2.5 Volts. Applied over 80 Ohms gives you 31mA, which is close to this info I found: "The typical CAN bus peak current consumption is about 30mA." But typical current is just 7mA. (2.5 Volts applied over 120 Ohms is 21 mA.)
It seems something else may be loading down your CAN bus to the point it doesn't work.
Why not tell us what is working and what is not. And what year your vehicle is.
I don't know if your measured 80 or 120 Ohms is typical. CAN bus voltage is 2.5 Volts. Applied over 80 Ohms gives you 31mA, which is close to this info I found: "The typical CAN bus peak current consumption is about 30mA." But typical current is just 7mA. (2.5 Volts applied over 120 Ohms is 21 mA.)
It seems something else may be loading down your CAN bus to the point it doesn't work.
Why not tell us what is working and what is not. And what year your vehicle is.
Thread Starter
Staging Lane
Joined: Apr 2023
Posts: 69
Likes: 7
From: Tx
09 g8 gt, and on my scan tool i cant see what is working or not, also simply havent been lucky finding a g8 ecu connector diagram so i could check voltage/resistance, also i unplugged my VCIM and i went to check ohms and it read O.L so a little stuck on what to do
Thread Starter
Staging Lane
Joined: Apr 2023
Posts: 69
Likes: 7
From: Tx
It sounds like your Ohm meter is simply charging a capacitor in the ECU; seems like very normal behavior. Pins 6 and 14 are the CAN bus high and low signal lines which go to places other than the ECU.
I don't know if your measured 80 or 120 Ohms is typical. CAN bus voltage is 2.5 Volts. Applied over 80 Ohms gives you 31mA, which is close to this info I found: "The typical CAN bus peak current consumption is about 30mA." But typical current is just 7mA. (2.5 Volts applied over 120 Ohms is 21 mA.)
It seems something else may be loading down your CAN bus to the point it doesn't work.
Why not tell us what is working and what is not. And what year your vehicle is.
I don't know if your measured 80 or 120 Ohms is typical. CAN bus voltage is 2.5 Volts. Applied over 80 Ohms gives you 31mA, which is close to this info I found: "The typical CAN bus peak current consumption is about 30mA." But typical current is just 7mA. (2.5 Volts applied over 120 Ohms is 21 mA.)
It seems something else may be loading down your CAN bus to the point it doesn't work.
Why not tell us what is working and what is not. And what year your vehicle is.
conclusion is i wonder if those two things not being connected would cause it to where i cant read the vehicle since they are the main power supply, and also i wonder if the negative and positive battery cables up front being connected and not disconnected like they should caused that mf to explode haha
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
@subeone - Thank you for telling us that 120 Ohms is normal.
@BrackenG8 - NOW you tell us what happened. Sorry to hear. I'm sure you have read the warning about how jump starting a car can damage the computer. Well, I suspect the huge voltage and current spikes caused by your short circuit likely did damage one or more computers, possibly the ECU.
@BrackenG8 - NOW you tell us what happened. Sorry to hear. I'm sure you have read the warning about how jump starting a car can damage the computer. Well, I suspect the huge voltage and current spikes caused by your short circuit likely did damage one or more computers, possibly the ECU.
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Thread Starter
Staging Lane
Joined: Apr 2023
Posts: 69
Likes: 7
From: Tx
okay just want to make sure we are on the same page, so it not allowing me to read my vehicle, could that be the reason alternator positive and starter negative not being connected, and you think with that huge spark from the battery blowing off the terminal end it could have messed something up and how would i even test something like that just test volts?
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