Codes U1000 and P0462

[w8lifter21]

Gotta love it when your car turns on lights for you for the holidays.

U1000 CAN Communication CircuitP0462 Fuel level sensor circuit low input

Anyone's Z/G throw these codes before? Aparently there is a TSB out for the U1000 that covers a wide range of Nissan/Infinity vehicles 2002-2006, TSB 06004.

A little debrief:Left a restaurant Xmas eve, VDC, Slip, AWD lights were on, gear indicator and tach did not work, car shifted a little harder than normal. Drove it the very short distance home, and proceeded to do the "Air Bag Light" reset. The lights went off but then the check engine light came on. Took the car for a quick spin and AWD, VCD, Slip worked normally. Xmas morning, fire it up, lights come on, do the air bag light reset and they go out, and I start the 4 mile drive to my parents. 1/2 way there, lights come on, CEL is still on. Leave Xmas night, start the car, only the CEL. Go home, then the video store, then back home, car drove fine, just the CEL. Get in the car today to go get breakfast, car just cranks, but does not run. Airbag light reset no longer works. Went and got two OBD2 scan tools, and pulled these codes.

Aparently CAN stands for Controller Area Network and it's basically two wires that all the other computers connect to when the car does a "system check" when the key is turned to IGN. Based on the TSB, just the ECM grounds that need to be cleaned and re-grounded. Only thing that concerns me is that I have tried two scan tools and neither one is able to clear the codes.

Help/Suggestions? Going to be checking fuses tomorrow morning.

[SteveTheTech]

Any of the U codes refer to a loss of connectivity or transmission capabilities through one of or both of the CAN lines. These wires are not only used to perform a rationality check but it also transmits vital signal information to all the major control units to keep the car operating correctly.

While I highly doubt that that bulletin applies to your incident (it has very specific verification criteria) I would not be surprised if you have a ground issue somewhere. The fuel level sensor uses both a power/signal wire and a detectable ground wire to set a code. If there was an incomplete ground causing a variance on the signal supplied to the ECM, thus the detection logic sets the code.

Not being able to erase the DTCs means they are current. This is not a diagnosis job for a rookie, I don't know your skill level but to properly diagnose this right without potentially damaging any of the control units. If you have a warranty I would strongly recommend taking it to them. If you are interested in doing this yourself I can try to help you but it will require you disassembling many things.

As a first quick check look at your battery cables. Are they clean and tight (wiggle them clockwise and counterclockwise), if they are dirty or loose, clean and re-tighten them. Also remove the battery cover and inspect the negative cable mounting on the passenger side inner fender. If the two 10mm bolts have any rust or corrosion on them remove them and clean the mating surfaces and re-install them.

(I would think about adding a layer or spray paint or some type of protective spray to the ground point, given your location)

There are several things that may cause this but checking these simple connections you will rule out the most common cause of the CAN dtcs.

Good Luck, and Happy New Year.

[NJ 666]

Clean and refasten all the grounds under the hood and for some reason it seems like the ground for the ABS actuator can cause a lot of problems for the CAN system.

[NJ 666]

Clean and refasten all the grounds under the hood and for some reason it seems like the ground for the ABS actuator can cause a lot of problems for the CAN system.

[w8lifter21]

Thanks all for the replies, I have done all of the above disconnected the ground and codes are still thrown. Off to the stealership I go...

[w8lifter21]

Is there anything behind the radio that could cause this light to trip? I recently installed an AVIC and my G has stock navi so it's a tight fit behind the radio, but I did my best to make sure all the wires are not pinched by anything back there.

[SteveTheTech]

That's definitely possible.

[w8lifter21]

Strange, wasn't aware that anything behind the radio would interfere with anything. I'll definitely pull it out again and inspect all the wires as well as the various module grounds before taking it in. Thanks for the info.