My 2018 Nissan Rogue has code U0284 (on cheap code reader). I paid an independent shop for a diagnosis, they also said it has code U1040, U1044, U1051 and U1000 linked to the "...active grille shudder system..." (his words) and that the grille shutter assembly needs to be replaced.
Their repair price was $1k. I denied the repair.

I discovered if I close the shutter flaps manually and clear codes. I can drive around and turn the car on/off. No code returns. Normally the code appears instantly. I was very excited.

When I park the car for a few minutes, immediatly when I start it up the flaps fully open and the code returns. It seems manually closing the flaps delayed the code coming back.

This is confusing, because the motor does open the shutters. Maybe the code appears when it fails to close the flap when I start up the car? Does it even try to do that though?
If I unplug the shutter actuator, I still have the battery light on dashboard and U0284 code.

The other codes he mentioned are worrying. Mechanic stated no communication with assembly.

Has body delt with this before?

Thanks so much in advance for anybody's input and your time!

Have a great day!

The U0284 is for the grille shutter, but the rest of those codes are all for the alternator. The two devices share a LIN line to the ECM, so there's a very specific procedure to find out what the problem is:
1) Unplug the alternator and start the car, see if the U0284 changes from "current" to "past". If so, the alternator is bad.
2) Plug the alternator back in and unplug the grille shutter, see if the U10xx codes go "past". If so, the shutter is bad.
3) If neither one makes any codes go past, you most likely have pinched wires in the grille shutter harness from a road debris impact.

Thank you for the quick response! Here is a picture of the grille actuator connection I inspected.

It's interesting that you mention the alternator. Yesterday, I had the battery disconnected, and was checking connections, I put everything back together, started the car, and went to open the back trunk. It sounded very weak and the motor stopped lifting it. I had to lift manually, and it wouldn't lift itself multiple times I tried. I've never seen that. Until I let the car run for a little bit and it was back at full power working fine.

Unfortunatly I have a cheap reader, I'm not sure if I can check for current or past specifically. It shows 2 U0284 codes if I clear codes, and no CEL. If I start the car it shows 4 U0284 codes with the last 2 having gibberish charset things next to the U0284, and the CEL is on. I will post pictures and alternator results tomorrow.

That's a scanner problem and you may need to check with the manufacturer to see how their unit specifies codes. Nissan specifies their codes as "current", "past", and "permanent" (P-DTC), and various scanners handle them in different ways. You might be able to simply erase the codes with one or the other device disconnected and see which ones come back.

I edited my post right before you commented.

To do your test must I disconnect the red hot wire and the sensor connector going to the alternator? Then run the car on battery a few seconds? Clear codes in between? Is that satisfactory? Thanks for your replies and help again.

EDIT: I may have got some windshield washer fluid in there. Is it worth getting the alternator tested? Thanks for your input again.

Not the big terminal on the alternator, just the smaller plug. It won't charge because the fields will be disabled with the connector loose, so yes, only run it for a short time.

Alternators aren't supposed to mind getting wet, so if washer fluid did it in then there was something wrong with it anyway.

VStar650CL wrote: ↑

Sun Mar 05, 2023 5:56 pm

Not the big terminal on the alternator, just the smaller plug. It won't charge because the fields will be disabled with the connector loose, so yes, only run it for a short time.

Alternators aren't supposed to mind getting wet, so if washer fluid did it in then there was something wrong with it anyway.

I ran a few tests like you said. When I unplugged the alternator sensor like you said, the 2nd picture is the results I received for 2-3 start ups in a row. When CEL is off, it only shows the 2 codes with weird characters at the end (pic #2).

Here is an example of what my code reader shows normally. The CEL is ON and it show's this


Here is an example of what shows when I unplug the alternator sensor, put the shutter flaps in the down position. The CEL is OFF but the code reader shows these codes.


I am thinking buying a grille shutter assembly is the best move? Nissan Part #21421-4BC0A. There seems to be a few $200 new chinese aftermarkets available. A genuine OEM nissan is about $400-450. Do people have good experience with aftermarket versions of grille shutter assemblies other Nissans?

In your experience? Should the other codes the mechanic mentioned be showing up on my cheap code reader? It appears the grille shutter is the only one I can see.
Thank you so much for your input again!!

Since the U0284 remained even with the alternator disconnected, that's conclusive, the grille shutter is offline. I don't have any direct experience with the aftermarket units, but the ones I've seen all appear to be clones or unbranded gray market. I'd say it's likely they're all made by the same China manufacturer making Nissan's OE shutters, but probably with lesser QC/QA standards. Whatever you choose, I do suggest plugging it in first without installing it. If the codes don't clear then you'll know you have a wiring or ECM issue and you can return the shutter before you make any tool marks. Chances are it actually is a bad shutter, but it won't hurt to hedge your bets.

It seems the 2nd picture didn't post. Here it is.
These are the codes that always show, even after clearing codes when the CEL is off. Manually closing flaps, and the alternator trick you mentioned both helped keep the CEL off for a bit. It was false hope. Eventually when starting up after a few times/short drives, the flaps would fully open, and the code returns. I didn't drive the car with the alternator sensor disconnected, but unplugging it did keep the code off for multiple startups.

I only type all this for the record to help others in the future.
Thank you for your input again.

The shutter does seem to only work (open) when it wants to. I will order a new grille shutter and follow your advice. As OEM and local as possible, so It's one less thing to worry about if it doesn't work :p

Thank you.

Thank you again so much for your input. I've been doing some r&d the past few weeks :p

I am on the hunt for a decent mechanic. This is a good summary of the issue at this point.

"Paid diagnosis showed code U0284 causing check engine light.

In addition, passive codes U1040, U1044, U1051, U1000.
Front air grille shutter was replaced.
The same codes persist, with or without either of the 2 shutter assemblies connected.

The codes and battery light initially showed when battery ground was removed from battery overnight. Maybe a short or wiring issue.
Accurate diagnosis and help needed!"


My plates are now expired as of march, because I cant get in inspected, and I dont know what to do. The past 2 shops I've been to have ripped me off for diagnosis fees, telling me nothing more then what I knew when I dropped it off. Man, life is full of surprises.

Accurate diagnosis is hard without a scanner which accurately reflects the status of the DTC's. However, there are only two devices on the LIN, the shutter and the alternator. So at this point it's either a bad alternator or a wiring problem, that's all that remains. If there's no wiring damage near the shutter (which is common from road debris), then it's very likely your alternator is shot.

I'll test the battery and alternator. Thanks

Is there any chance that the alternator is able to keep the car/battery going but it's the additional small sensor attatched to it thats bad? The one that was mentioned to unplug for diagnosis.

If both the alternator/battery come back in OK condition, does it make sense to investigate wiring issues somewhere in between?

Grille shutter is replaced. Now I will get the alternator/battery diagnosed. I will keep updated!

Thank you!!!

beigmatt wrote: ↑

Sat Apr 15, 2023 4:49 am

Is there any chance that the alternator is able to keep the car/battery going but it's the additional small sensor attatched to it thats bad? The one that was mentioned to unplug for diagnosis.

The alternator will just self-regulate if it can't hear the ECM on the LIN line, so it won't normally cause charging problems, just codes. No to the second question, you'd be getting a P155x code (probably P1552) if the Battery Current Sensor was acting up. That's a voltage output and not associated with the LIN.