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Hi ,l have a nissan np300 yd25 engine that has been driving just fine ,recently got the pump serviced ,it run for 2 days just fine then it just cut whilst driving. The engine will crank but not start .The pump seems to be producing enough pressure ,The problem is it's not showing the engine management light and key light which normally beeps even if the key is not in the ignition. The diagnostic machine wont read the ECU ,l have tried a different Ecu but still same problem diagnostic wont get in to read the ecu,l have checked all the fuses and they seem to be ok ,can anyone please with information on what could be the problem, Thank you
 

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Discussion Starter #3
Thanks
I had another Ecu installed but still could not read which leaves me think maybe its electric problem
 

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That sounds to me like it is likely to be a databus problem. If the ECU was at fault then when you swapped it still wouldn't start but you would have communication. A high speed databus/network issue can affect communication between modules preventing starting and also preventing OBD port communication.

You need to find someone who understands databus/networks to diagnose and fix.
 

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You can't just put another ECU in, it is linked to the Nissan security system so needs some coding using Nissan consult.
 

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Discussion Starter #6
That sounds to me like it is likely to be a databus problem. If the ECU was at fault then when you swapped it still wouldn't start but you would have communication. A high speed databus/network issue can affect communication between modules preventing starting and also preventing OBD port communication.

You need to find someone who understands databus/networks to diagnose and fix.
I will
That sounds to me like it is likely to be a databus problem. If the ECU was at fault then when you swapped it still wouldn't start but you would have communication. A high speed databus/network issue can affect communication between modules preventing starting and also preventing OBD port communication.

You need to find someone who understands databus/networks to diagnose and fix.
Ok l will do ,but still cant get an explanation why the key light isn't showing on the dashboard display ,thanks
 

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You can't just put another ECU in, it is linked to the Nissan security system so needs some coding using Nissan consult.
Correct if l am wrong, from my understanding ,it should read /or show an Ecu is plugged but wont start ,but it wouldn't when another ecu was installed
 

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I will

Ok l will do ,but still cant get an explanation why the key light isn't showing on the dashboard display ,thanks
The security on your car will be controlled by the BCU (or similar, all manufacturers refer to this as something different but it's the same thing). It will send information to the dash, sometimes to a separate ECU, sometimes a direct feed to a bulb (depends on vehicle) telling it the status of the locks etc. It also communicates with the PCM (engine computer) to allow/prevent starting. If the high speed network (communication network between various ECUs) is interrupted then it can't do this.

The task now is to find what is causing the failure of communication on the high speed network. This can be within a component, within an ECU or within the databus/network wiring somewhere in the vehicle.
 
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