How to determine a bad ECU?
10-08-2006, 12:14 PM
#3
generally ECU's dont go bad. unless the ECU has been moddied or chipped. give us your symptoms and why you are saying your ECU is bad.
I've seen 1 ECU go bad in my life so far. it would throw a fault for the evap and when tested 1 out of 10 times it would fail throwing a light on. And there was a bullention with a concern about the value ranges on that particular ECU was set wrong.
I've seen 1 ECU go bad in my life so far. it would throw a fault for the evap and when tested 1 out of 10 times it would fail throwing a light on. And there was a bullention with a concern about the value ranges on that particular ECU was set wrong.
10-08-2006, 12:15 PM
#4
A dead ECU will result in a non-starting Maxima. EXTREMELY rare - maybe one in every 50'000 and usually from boosting a car whose electrical is screwed. Also, if your car received a jolt from a lighting strike or one near by, it will also fry the ECU if it can't ground the charge.
There are a lot of problems that can go in the Maxima engine that will take time to post a code.
Do a basic test on your ECU - pull the plug on an injector or the MAF sensor (grey plug just after the air box). It should throw those codes immediately (CEL). Pull the code and reset the ECU. If it doesn't CEL, then your ECU may be faulty.
Bad ECU's 99.9% mean a dead car.
There are a lot of problems that can go in the Maxima engine that will take time to post a code.
Do a basic test on your ECU - pull the plug on an injector or the MAF sensor (grey plug just after the air box). It should throw those codes immediately (CEL). Pull the code and reset the ECU. If it doesn't CEL, then your ECU may be faulty.
Bad ECU's 99.9% mean a dead car.
10-08-2006, 01:31 PM
#5
Ok so here is the story.
Today i changed the Coolant temp sensor. It was faulty cause my car kept overheating because the radiator fans would not turn on when the motor temp gauge got more than 1/2 way. I diagnosted everything from fuses to relays to both fan motors and they all checked fine.
After i changed the Coolant temp sensor everythiing worked on the first run. The fans came on when the temp gague showed more than 1/2. I go to church and come back and the car would not start. When i try to crank it i saw and smelled smoke comming from the gauge cluster. It smelled like something was shorted. First thing i did was change the battery because they said it was bad.
After i changed the battery the car started up fine, but when i started driving my guage lights started to flicker and my Tach is dead. Also the radiator fans do not turn on anymore and the car overheats.
I didnt touch anything but the coolant temp sensor and now all of a sudden the tach goes dead. The radiator fans do not turn on themselfs anymore.
My guess is that the ECU is bad because it is not sending a signal for the fans to turn on. Also my Tach is dead and lights on the gauge cluster flicker when i hit bumps.
Also after i reset the ECU no lights come on. Before i had code 0402 - fuel tank temp sensor.
So how do i know if the ECU is bad> Can i get it tested at Nissan? I cant think of any other reason why the car keeps overheating because the fans do not turn on.
Any help appreicated!!
Today i changed the Coolant temp sensor. It was faulty cause my car kept overheating because the radiator fans would not turn on when the motor temp gauge got more than 1/2 way. I diagnosted everything from fuses to relays to both fan motors and they all checked fine.
After i changed the Coolant temp sensor everythiing worked on the first run. The fans came on when the temp gague showed more than 1/2. I go to church and come back and the car would not start. When i try to crank it i saw and smelled smoke comming from the gauge cluster. It smelled like something was shorted. First thing i did was change the battery because they said it was bad.
After i changed the battery the car started up fine, but when i started driving my guage lights started to flicker and my Tach is dead. Also the radiator fans do not turn on anymore and the car overheats.
I didnt touch anything but the coolant temp sensor and now all of a sudden the tach goes dead. The radiator fans do not turn on themselfs anymore.
My guess is that the ECU is bad because it is not sending a signal for the fans to turn on. Also my Tach is dead and lights on the gauge cluster flicker when i hit bumps.
Also after i reset the ECU no lights come on. Before i had code 0402 - fuel tank temp sensor.
So how do i know if the ECU is bad> Can i get it tested at Nissan? I cant think of any other reason why the car keeps overheating because the fans do not turn on.
Any help appreicated!!
10-08-2006, 01:34 PM
#6
Originally Posted by TurTLe*
generally ECU's dont go bad. unless the ECU has been moddied or chipped. give us your symptoms and why you are saying your ECU is bad.
I've seen 1 ECU go bad in my life so far. it would throw a fault for the evap and when tested 1 out of 10 times it would fail throwing a light on. And there was a bullention with a concern about the value ranges on that particular ECU was set wrong.
I've seen 1 ECU go bad in my life so far. it would throw a fault for the evap and when tested 1 out of 10 times it would fail throwing a light on. And there was a bullention with a concern about the value ranges on that particular ECU was set wrong.
I had a evap code before this all happened, but it would come on and off once in a while. I would check the codes and it would throw 0302, but the light didnt come on. Could i possibly have a bad ecu?
10-08-2006, 02:04 PM
#7
hey, this is just a thought. i dont know the whole electrical system of a nissan but i work on VW's daily. and on VW's fans are controlled by the temp sensor and that sends signal to fan control module that turns on the fans. if your fans dont kick on then it can be either faulty fan control module or WATER PUMP!!.
check the flow of your coolant. when you changed your sensor did you top off coolant and boil out all the air pockets you could of caused? ECU's can not be tested, a simple way is to plug in a scan tool if it reads its not faulty.
the evap code has nothing to do with it. again i was talking in terms of VW.
from everything you said you have other issues and its not the ECM. it would not cause your car to crank slow, that is a starting, charging issue. maybe a bad cam/ crank signal. a tach not reading could be vechile speed sensors. most speed sensors should create AC volt when you spin the wheel.
i'm going with that fact that your ECM is operating fine and you need to look at all your problems one by one. i would go back to your coolant sensor first and make sure everything is working and you have strong coolant flow, since a car overheating could be fans, water pump, bad coolant, air pockets,
check the flow of your coolant. when you changed your sensor did you top off coolant and boil out all the air pockets you could of caused? ECU's can not be tested, a simple way is to plug in a scan tool if it reads its not faulty.
the evap code has nothing to do with it. again i was talking in terms of VW.
from everything you said you have other issues and its not the ECM. it would not cause your car to crank slow, that is a starting, charging issue. maybe a bad cam/ crank signal. a tach not reading could be vechile speed sensors. most speed sensors should create AC volt when you spin the wheel.
i'm going with that fact that your ECM is operating fine and you need to look at all your problems one by one. i would go back to your coolant sensor first and make sure everything is working and you have strong coolant flow, since a car overheating could be fans, water pump, bad coolant, air pockets,
10-08-2006, 02:22 PM
#8
Originally Posted by TurTLe*
hey, this is just a thought. i dont know the whole electrical system of a nissan but i work on VW's daily. and on VW's fans are controlled by the temp sensor and that sends signal to fan control module that turns on the fans. if your fans dont kick on then it can be either faulty fan control module or WATER PUMP!!.
check the flow of your coolant. when you changed your sensor did you top off coolant and boil out all the air pockets you could of caused? ECU's can not be tested, a simple way is to plug in a scan tool if it reads its not faulty.
the evap code has nothing to do with it. again i was talking in terms of VW.
from everything you said you have other issues and its not the ECM. it would not cause your car to crank slow, that is a starting, charging issue. maybe a bad cam/ crank signal. a tach not reading could be vechile speed sensors. most speed sensors should create AC volt when you spin the wheel.
i'm going with that fact that your ECM is operating fine and you need to look at all your problems one by one. i would go back to your coolant sensor first and make sure everything is working and you have strong coolant flow, since a car overheating could be fans, water pump, bad coolant, air pockets,
check the flow of your coolant. when you changed your sensor did you top off coolant and boil out all the air pockets you could of caused? ECU's can not be tested, a simple way is to plug in a scan tool if it reads its not faulty.
the evap code has nothing to do with it. again i was talking in terms of VW.
from everything you said you have other issues and its not the ECM. it would not cause your car to crank slow, that is a starting, charging issue. maybe a bad cam/ crank signal. a tach not reading could be vechile speed sensors. most speed sensors should create AC volt when you spin the wheel.
i'm going with that fact that your ECM is operating fine and you need to look at all your problems one by one. i would go back to your coolant sensor first and make sure everything is working and you have strong coolant flow, since a car overheating could be fans, water pump, bad coolant, air pockets,
The coolant flow is fine. Nissans work in the same way excpet the sensor tells the ECU to turn the fans on. A signal is sent from the ECU to the relay to turn on the fans. So it could possiblie be the ECU.
BUT, i just check the operation of the fans and they seem to be working now. The only problem i have left is figuring out what burned up in my car and why the Tach doesnt work.
10-08-2006, 02:47 PM
#9
Originally Posted by Fork
A dead ECU will result in a non-starting Maxima. EXTREMELY rare - maybe one in every 50'000 and usually from boosting a car whose electrical is screwed. Also, if your car received a jolt from a lighting strike or one near by, it will also fry the ECU if it can't ground the charge.
There are a lot of problems that can go in the Maxima engine that will take time to post a code.
Do a basic test on your ECU - pull the plug on an injector or the MAF sensor (grey plug just after the air box). It should throw those codes immediately (CEL). Pull the code and reset the ECU. If it doesn't CEL, then your ECU may be faulty.
Bad ECU's 99.9% mean a dead car.
There are a lot of problems that can go in the Maxima engine that will take time to post a code.
Do a basic test on your ECU - pull the plug on an injector or the MAF sensor (grey plug just after the air box). It should throw those codes immediately (CEL). Pull the code and reset the ECU. If it doesn't CEL, then your ECU may be faulty.
Bad ECU's 99.9% mean a dead car.
1. Engine speed will be limited to 3000 RPM.
2. Simultaneous fuel injection will be used instead of sequential.
3. The radiator fans will be on HIGH mode full-time when the engine is running.
* taken from the Fail-Safe Chart in the EC section of the FSM.
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