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Unread 03-28-2010, 01:30 PM   #1
lexinator02
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How can I tell if my ECU is shot? SHE STARTED!!!

I have a 90 yj with a 2.5L and a 5 speed and I am pretty sure my ECU is shot. Is there any ways I can use a mulitmeter to see if it is shot or do I just have to bite the bullet and buy a new one to see?

Dave

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Last edited by lexinator02; 03-31-2010 at 04:22 PM..
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Unread 03-28-2010, 04:35 PM   #2
laybackman
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Quote:
Originally Posted by lexinator02 View Post
I have a 90 yj with a 2.5L and a 5 speed and I am pretty sure my ECU is shot. Is there any ways I can use a mulitmeter to see if it is shot or do I just have to bite the bullet and buy a new one to see?

Dave
When you turn your ignition to the ON (not START) position and your various dash gauges light, up does your CEL come on also? If it does it is probably OK.
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Unread 03-28-2010, 04:57 PM   #3
Que89YJ
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Its a 1990 so it predates the SMEC or the SBEC so the CEL light isnt a good indicator. I guess the better question is why do you think the Engine controller is bad? Whats wrong with your jeep?
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Unread 03-28-2010, 06:20 PM   #4
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Its a 1990 so it predates the SMEC or the SBEC so the CEL light isnt a good indicator. I guess the better question is why do you think the Engine controller is bad? Whats wrong with your jeep?
Since it was a 2.5 I thought it was since it has TB injection. But you are right that all started in '91 didn't it? But the good question is what you asked the OP..why do you think it needs to be replaced?
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Unread 03-29-2010, 06:03 AM   #5
lexinator02
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http://www.jeepforum.com/forum/f12/a...st-lol-991642/

I have this thread going I just wanted an individual question about the ECU. I would love an answer like take a multimeter at all these plugs on the ecu harness and you should get this value. That way I would know if the inputs and outputs are normal.

Dave
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Unread 03-29-2010, 11:13 AM   #6
laybackman
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Originally Posted by lexinator02 View Post
http://www.jeepforum.com/forum/f12/a...st-lol-991642/

I have this thread going I just wanted an individual question about the ECU. I would love an answer like take a multimeter at all these plugs on the ecu harness and you should get this value. That way I would know if the inputs and outputs are normal.

Dave
You would need to know the electrical values of all the pinouts on the brain whether they be input OR out put voltages. A FSM is the best place for that information.
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Unread 03-29-2010, 11:21 AM   #7
lexinator02
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well for the heck of it I decided to open up the ECU and check it out. I found a capacitor/resister completely burnt and cracked and the backside of the board was burnt in that spot as well so I think its safe to say my ECU is shot lol

Dave
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Unread 03-29-2010, 02:24 PM   #8
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well for the heck of it I decided to open up the ECU and check it out. I found a capacitor/resister completely burnt and cracked and the backside of the board was burnt in that spot as well so I think its safe to say my ECU is shot lol

Dave
This link goes to one of several fixes for bad capacitors in a brain;
http://www.jeepforum.com/forum/f12/c...rs-ecu-492597/
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Unread 03-29-2010, 03:03 PM   #9
Que89YJ
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He has the renix controller on the Renix controller on the inside of the vehicle. Its the first time I heard of this happening. Pics would be appreciated. I agree though. It should be similar in the issues as the Sbec and it should be repairable. The cao should be on the input pin for power and should be easily replaced. A resistor would be a new one for me too.
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Unread 03-29-2010, 03:13 PM   #10
lexinator02
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Here are some pics of what I found. I could not tell if it was a resistor or capacitor...










Dave
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Unread 03-29-2010, 03:39 PM   #11
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Originally Posted by lexinator02 View Post
Here are some pics of what I found. I could not tell if it was a resistor or capacitor...










Dave
I think it is a big resistor. What you need to know is what was it's value. Can you see the stripes on it? That gives you the value.

Resistor Color Code Table And Calculator
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Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

"If we cannot afford to take care of Veterans, then we should stop making them."
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Unread 03-29-2010, 04:15 PM   #12
lexinator02
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no its solid black from being burnt. It does look a lot like the resistor in the 2nd pic though...
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Unread 03-29-2010, 04:26 PM   #13
wrangler76
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Does the "R125" on the board specify anything useful?
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Unread 03-29-2010, 04:32 PM   #14
JOExFROMxNY
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Does the "R125" on the board specify anything useful?
R=resistor
D=diode
C=capacitor

Look for a number underneath it. That "R" might be for the resistor next to it.
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Unread 03-29-2010, 04:33 PM   #15
laybackman
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no its solid black from being burnt. It does look a lot like the resistor in the 2nd pic though...
That was my thought also it does look quite similar. I wouuld look inder the burntt one also and see if you can see any hint of the stripe(s) on it OR find one that is the same size and see what it's value is. Then buy one and swap out the bad one for the new one....What have you got to lose at this point?
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Chicks dig me.....Fish fear me

Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

"If we cannot afford to take care of Veterans, then we should stop making them."
David C. Wilker Jr. USAF (RET)
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