disconnecting battery

[bill flyer]

hi to all I have just brought a narvara d40 2009 auto and i would disconnect the battery , it states in the book that you have to do certain things to reinstate the alarm system is this true, or can i just put the terminals on and all will be ok . i know its a strange question but i don't want any trouble first up . cheers

 

[Aussie Frontier]

Not 100% sure on later models but on my 07 D40 I disconnect the battery regularly to reset the ECU.To date never had any issues at all other than maybe having to reset the auto window for the drivers door

 

[Old.Tony]

Welcome aboard.

Same car here, no troubles with disconnecting the battery. Same caveat with the window too - easy enough to fix as well (hold it down so that it reaches the bottom, then bring it up to the top and hold it up for a decent 5-count).

ECU will still have a little stored power unless the battery's disconnected for 30+ minutes, but you can shorten that by stabbing the brake pedal (consumes any residual power in very short order).

The NATS (Nissan Anti Theft System) is self-restarting. If you have an after-market alarm that actually does something other than flashing a red light then you'd have to refer to their manual.

 

[Knickers]

as a newby, what is the reasoning for resetting the ECU? Is it something that needs doing occasionally to keep things running OK, or is there something that tells me it need a reset, i.e. loss or power, running rough or poor fuel economy?

 

[Old.Tony]

There are a number of reasons to reset the ECU, the most common being to reset the fuel learning map and to clear error codes that might have tripped up the ECU into a limp mode - for example, a dirty MAFS will trigger a code and put the car into limp mode, so you clean the MAFS, reset and worry no more.

 

[Knickers]

Should a reset be performed after doing an EGR blank?

 

[Old.Tony]

I don't see the need. The computer is blissfully unaware that it's choking on its own exhaust, and that's the way it ought to be!

 

[bill flyer]

to old tony and others re disconnecting the battery .thanks for all your help with this matter

 

[Tappet]

as a newby, what is the reasoning for resetting the ECU? Is it something that needs doing occasionally to keep things running OK, or is there something that tells me it need a reset, i.e. loss or power, running rough or poor fuel economy?

I to have wondered the same thing. Like I understand the reasoning for an ECU reset. However in a the Diesel powered D40's I wonder how the fuel, or injection timing is altered, or if it really is at all. On a petrol it is a very real thing and load points do change as the motor wears and becomes tired but it has an O2 sensor in the exhaust to give feed back to the ECU. What is called "closed loop". Simply put, sniff out what is coming out to ensure you have the right AFR going in. This only happens with a steadish throttle position in top or the higher gears in other situations the ECU disregards the output from the O2 sensor. If the engine is constantly running lean the ECU shifts the load point (MAP) to richer.
So in the Diesel version how does it do it? Does it look at the relationship of MAF to throttle position to engine speed, perhaps even road speed in the equation as well?? If it does reset to some predetermined value. Where is the gain? Fuel consumption could very marginally decrease but along with a drop in performance.

I to have done a couple of resets with no difference in performance and or fuel consumption at all. Not saying it didn't do anything but I could not detect anything.

 

[Old.Tony]

Supposedly - and while it might all be guff and bunkum, enough people have done ECU resets to counter the bunkum argument - the ECU learns your driving style and adjusts the fuel mapping accordingly.

In precise terms, I don't know what that actually means. Does it mean it varies the fuel rail pressure for a given throttle position/speed/load/gear? Does it fiddle with the timing based on those variables?

Here's a better question - why would it alter the fuel mapping from the most fuel-efficient to something else based on anything at all? Is it to anticipate the surge required when stopped at the lights beside a Hilux (and how does the car know it's a Hilux)?

All I do know for fairly sure is that after resetting the ECU, the car does seem to change back to a less fuel-hungry map until you teach it otherwise again. People have said - and I've repeated in the past - that this is the "factory default" mapping which is then modified to your driving style. Doing the ECU reset also removes the factory-shipped setting (not the default, but the mapping the vehicle is shipped with) which is supposedly quite rich, in order to let the engine run cooler while the components are all bedding in.

Fact or fiction? I don't know. Anyone good at Assembler want to reverse engineer the ECU?