DTC U1000, U1001: CAN Communication Line - Nissan Murano Forum
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post #1 of 12 Old 08-31-2009, 08:05 PM Thread Starter
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Exclamation DTC U1000, U1001: CAN Communication Line

Since grounding issues seem to be common on the MO, and the answers are spread all over the board, I made a thread specific to the U1000/U1001 Diagnostic Trouble Code (DTC).

Usually this ends up being a loose grounding bolt holding the ECM to the dash bar, causing the ECM to lose ground temporarily. Many with this DTC complained of hesitation, stalling or the engine holding a lower than normal RPM. For me, I was cruising at about 45 MPH, the engine dropped to about 500 RPMs, began shuddering, and the SES light came on. The engine did not respond to the gas pedal and at about 15 MPH it stalled. I got over to the shoulder and tried to restart but it did nothing. It was like when you try to start with a completely dead battery; no sound. But I had full electrical power since the lights/radio/air was on. 5 minutes later, it started back up as if nothing had happened. Check Engine light remained on, and until it was looked at by a mechanic was a bit hesitant during acceleration.
Had my mechanic retighten the various connections. He left SES light on (didn't clear code). That way if he didn't fix the issue, a dealer would have the code to go by (dealers won't take your word, they need the code). About a week later the SES light turned off and the issue has not returned.

TSB EC06-001A
Relates to DTC U1000/U1001

Description
"CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are conected with 2 communication lines (CAN H line, CAN L line) allowing a high rate of information transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only."

DTC Detecting Condition
-ECM cannot communicate to other control units.
-ECM cannot communicate for more than the specified time.

Possible Cause
-Harness or connectors (CAN communication line is open or shorted).

When an issue with the CAN arises (at least twice in one trip), it triggers the Service Engine Soon (SES) light on the dash.

TSB EC06-001A Actions
When this code is brought on by a grounding issue, these are the steps the mechanic will follow to remedy.
-Clean/re-tighten ECM ground connections.
-Clean/retighten negative battery cable body connection and battery post connection.
-If needed, clean and ensure good contact between the steering member assembly and the left side instrument stay assembly.

__________________________________________________ _________________________________________________

Quote:
Originally posted by vistokid
"Found U1000 Can Com code. This code is caused by ECM not getting proper ground. This is due to ECM is grounded through dash bar to vehicle body and bolts connecting dash bar to body become loose and ground is temporarily lost. Retorqued bolts and erased code light."

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Quote:
Originally posted by njjoe
I had the C1000 (same as U1000) grounding problem three years ago. The fix was simple (tightened a grounding bolt under the dash) and took less than an hour. My records show they implemented Service Bulletin #EC06-001a... I was a bit skeptical when they claimed all they did was tighten a ground connection, so they printed out the SB as proof. The problem never returned. It was repaired under the bumper-to-bumper warranty.
Quote:
Originally posted by PearlMurano
I went to Nissan today and they checked the SES code. Turns out it was code U1000 communication failure, ECM ground failure. They removed the dash and cleaned contacts at ECM and harness and secured connections. All is going well so far. Seems to have fixed my problem. Tech said that the murano was well known to have electrical problems of this type.
This should be covered under the 3/36 bumper-bumper, although you might have to fight for it. This is NOT covered by the powertrain warranty.

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post #2 of 12 Old 08-31-2009, 08:13 PM Thread Starter
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post #3 of 12 Old 09-02-2009, 08:31 AM
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Like in the other thread, where exactly is this gounding bar located? I'd like to dive into the service manual and create a set of step by step instrucitons to fix this. There is no need for us to have to pay over $100 for something simple.

Anybody know?

After 142K miles, my MO is history. Now sporting a loaded silver 2012 Ford Edge Limited with 20" wheels.
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post #4 of 12 Old 09-04-2009, 06:56 AM Thread Starter
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Quote:
Originally posted by Warhammer
Like in the other thread, where exactly is this gounding bar located? I'd like to dive into the service manual and create a set of step by step instrucitons to fix this.

Anybody know?
njjoe,

You mentioned in a previous thread that the dealer circled the location of the bolt (on the grounding bar) that they tightened. Do you happen to still have the service invoice? I'd rather not have to take it to the dealership for this ridiculous adjustment.

Isn't it shown on the Service Manual?

Patrick

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post #5 of 12 Old 06-10-2010, 10:43 AM Thread Starter
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U1000/1001 Strikes Again!


Update:

Since my mechanic cleaned the terminals (NOTE: he didn't tighten the grounding bolt on the bar behind the dash), the MO has been drivable but sometimes acted strangely. In the last few months though, it's been acting up more frequently. When cruising, it will randomly rev the engine up, then drop back down to cruising revs. It happens intermittantly and without a obvious cause (constant pressure on gas pedal, flat terain, etc.).

A week ago, SES light popped up and it stalled out again while driving. I waited a bit, started it up but it was idling too low and rough, so I got it towed to my mechanic. Thank god for AAA! Mechanic pulled the U1000/1001 code again plus P1720 or P1704 (I can't remember), which was a speed sensor issue. He said the reving symptoms were consistent with that type of issue. Unfortunately, troubleshooting this type of communication issue is over his shop's capabilities and he advised me (gulp) to take it to a dealer. I've been too busy to drop it off. The SES light turned off in the mean time.

Last night I believe the BRAKE + ABS light came on at the same time and the engine went screwy. The warning lights were only on for about a second, then the engine seemed to have trouble transferring all power to the wheels. The engine was reving much higher than usual to get it/keep it moving. This symptom went away after about 30 seconds and the SES light never came on. I know BRAKE plus Battery is dying alternator, but what does BRAKE plus ABS mean? Could these all be symptoms of a dying speed sensor or an overall grounding issue? Any advice would be appreciated, thanks.

Patrick
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post #6 of 12 Old 06-10-2010, 03:24 PM
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Since a lot of people have had grounding issues, I am going to suggest that here.

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post #7 of 12 Old 03-01-2012, 08:42 PM
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Can anyone point out the bolts that get loose? Are they in the engine compartment? Or behind the dash?? This just happened to our MO.
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post #8 of 12 Old 03-01-2012, 09:30 PM
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Has anyone actually fixed this problem by themselves? I cant see a grounding bar behind the ECM or on the fire wall. Probably to much stuff in the way. LOL
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post #9 of 12 Old 03-03-2012, 09:17 AM
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I found the grounds. Both are behind the dash bolted to a bracket on the steering mount bar. One is above and just to the left of the steering column, The other is on the passenger side behind the air bag. You have to drop the column and remove just about the whole dash to get to them. PIA.

Code is cleared and problem is gone, hopefully for good.
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post #10 of 12 Old 03-28-2012, 11:24 AM
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Lightbulb Low power caused my issues

My '05 Murano started acting strange. To the point that nothing would happen when I press the accelerator after driving for 10 minutes. When I checked for codes, I got a handful that were all over the place: u1000, p0725, p0746, p0703, p0615, p0868. None of the codes seemd related at all (transmission pressure, speed sensor, one was for brake lights or something, etc...)

The u1000 code was the key. After 3 days of troubleshooting, I tested the battery. It was bad! Apparently, there was enough power to start the car, but in doing so, prevented some of the sensors from communicating properly.

Once I replaced the battery, the codes went away and haven't come back. I've been able to get a whole day of driving in so far with no recurring issues.

So, before you start to search for those pesky grounds behind the dash, test your battery!
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post #11 of 12 Old 03-28-2012, 02:00 PM
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Quote:
Originally Posted by effinay View Post
So, before you start to search for those pesky grounds behind the dash, test your battery!
Welcome to the forum!

Out of curiosity, was that the OEM battery that failed in your '05?

-njjoe

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post #12 of 12 Old 05-07-2012, 03:09 PM Thread Starter
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Lightbulb

My issue was resolved a while back but I just realized I didn't update this thread. My saga ended after 719 days (1.5 weeks shy of 2 years) and replacement of the CVT, transfer case, transmission control module, engine control module, anti-lock brake system module, primary speed sensor, intake duct, battery, addition of a grounding strap, servicing of the grounding points 6 times, 3 flatbed tows, 3 loaner cars, 16 trips to 2 different dealers, $24,000+ in warranty work and 41 total days in the shop. It turned out to simply be a loose harness in the IPDM. The harness connectors weren't damaged, and once clipped in properly, the MO started and never had another issue.

They believed the harness was in place but not (and possibly never been) properly clipped into place, creating resistance and intermittent power loss. The fluctuating power / corrupted data confused the ECM causing poor driveability. Acute power/data interruption would send the tranny into fail-safe mode and spit out a half dozen codes.

See this thread for more info: You're not going to believe this...
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