G35 sedan 2003 won't crank or start in cold weather...help needed please

[Bernard V.]

As long as the engine is warm the car will start but once cooled off and in cold weather il will not crank or start. Other caracteristics of the problem: The headlights and tail lights were flicking really quickly as engine was off and no keys in ignition ( once ) . The same happenned ( once )with the indicators above the clock. When the engine starts ( milder weather) several indicators light up and gradually dissappear. (The engine service soon indicator as well. ) The codes results are ;can-comm circuit ( u1001)can comm circuit ( u1000) vent control valve ( p0447)nats malfunction (p1615)I need help figuring out what part needs to be replaced first...I should tell you as well that the car has a distance car starter wth no anti-start device. Can the broblem de related to it...Has anyone had this problem already and what was the solution...? Thanking you in advance

[audtatious]

Have you checked the voltage at the battery? Cold can cause issues with weak batteries and charging systems.

[SteveTheTech]

As long as the engine is warm the car will start but once cooled off and in cold weather il will not crank or start. Other caracteristics of the problem: The headlights and tail lights were flicking really quickly as engine was off and no keys in ignition ( once ) . The same happenned ( once )with the indicators above the clock. When the engine starts ( milder weather) several indicators light up and gradually dissappear. (The engine service soon indicator as well. ) The codes results are ;can-comm circuit ( u1001)can comm circuit ( u1000) vent control valve ( p0447)nats malfunction (p1615)I need help figuring out what part needs to be replaced first...I should tell you as well that the car has a distance car starter wth no anti-start device. Can the broblem de related to it...Has anyone had this problem already and what was the solution...? Thanking you in advance

There are several things that can cause the u codes. They all have different definitions with generic descriptions. The vent ctrl valve and NATS malfunction are not good. I would not suspect the components themselves.

The NATS code is most likely a by-product of either low reserve capacity in your battery and in the fraction of a second from the point when you turn the key and the time the RFID number is registered with the security unit (BCM) if the battery voltage is too low to support adequate signal transmission a DTC may set.

The vent control valve may be one or two of several possibilities. Given your location and vehicle age I would suspect the valve may indeed be bad they tend to rust when exposed to salt climates. This also may be a by-product of a bad ground, all of these DTCs may be set by a corroded or incomplete ground.

If there is no transmission from the combination meter or any control unit for that matter a U code can be set. These require slight above basic diagnostic skills and I do not know if it will be easy without a Consult handy.

[jwerty1]

most of the u codes ive had are negative battery terminals that are corroded, or not connected properly or a bad ground somewhere, i would highly suspect your battery before anything for those

as for the p0447 i would almost definently say bad vent control valve

as for the nats malfunction, take it to a nissan or infiniti dealer, your key may be bad, or if you have any spare keys that are not registered to the vehicle and you tried starting with those

i haven't seen bad keys unless they were aftermarket keys however

[Bernard V.]

Thank you for the reply,

When i put the key in the ignition the dashboard lights will go on no problem but car will not crank. Is it still possible that the problem be related to the battery....Thanks

[Bernard V.]

Thank you for the reply,

Checking the battery i noticed there is a lot of thick grease around the neg. pole....Can this be the problem....Thank you..

[jwerty1]

it could be, if the vehicle will flat out not crank, it is not getting enough power to engage the starter, the cables could be getting enough juice to power the dash lights, but not enough to engage the starter intermittently

i would start by removing both battery cables, cleaning them thoroughly, as well as the battery terminals themselves, also i believe there is an important body ground on these behind the battery by the firewall, not positive though, only can really get to it with the battery removed, but at least shine a light in there to see that it is connected properly

if the nats code was a problem the vehicle would crank and crank forever and not let the vehicle start, it will not keep the vehicle from cranking

a dead/weak battery, or bad connection will keep the vehicle from cranking

these are obviously best case scenarios, normally the only thing that keeps these cars from starting is a bad battery, if that doesnt fix it, you may want to take it to a respectable shop

[Bernard V.]

Thanks again for the reply,

having boosted the battery ( with a booster pack ) and getting no crank, does that eliminate the battery problem... Thank you

[jwerty1]

maybe, maybe not, did you clean and reconnect the cables?

[jwerty1]

making sure they don't twist and turn on the vehicle

[jwerty1]

making sure they don't twist and turn on the vehicle, if the vehicle ever does start, take it to autozone and have them test the battery for free