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Unread 11-14-2011, 11:16 AM   #1
nyurdrms
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Need Help with Rare Code Error - U0155

Hi all,

I've searched the Forum for about an hour now and although people have posted about this, I can't nail down a thread that's exactly like this.

Here's the problem. I take the 05 Wrangler X in for inspection, Jeep runs fine so I'm expecting no issues (check engine has never come on in 3 years). And, the guy rolls it out of the Bay and says my check-engine is on and reading a code U0155 (here is the meaning of this)

U0155 LOST COMMUNICATION WITH CLUSTER/CCN
U0155 LOST COMMUNICATION WITH CLUSTER/CCN (SKREEM)
U0155 LOST COMMUNICATION WITH CLUSTER/CCN
U0155 LOST COMMUNICATION WITH CLUSTER/CCN
U0155 LOST COMMUNICATION WITH CLUSTER/CCN

So, I tell him that it literally just came on when he hooked up the machine. Now, I've got the "Rejected" sticker up front and 60 days to cure the problem.

I cleared the code that night, drove it 200 miles and it never came on again. 2 weeks later (today) I roll the Jeep back to the same place, they plug it in and the light comes on! They swear they've never had this problem so its probably my Jeep.

Other posts/replies indicate everything from a bad PCM, a bad cluster, wiring shorts..etc. But why is it only coming on when they hook up to the Registry for Inspection?

I did buy it 3 years ago with a Gorilla alarm installed and no alarm-key and earlier this year (since last inspection) as I was driving the siren started blaring. So, I pulled over and yanked out the red/black wires from the Speaker and I suppose they're still just hanging there. Could the aftermarket alarm open wires be doing this? Or is there a better chance of a guage/PCM issue?

Any help would be GREATLY appreciated! If I don't have it fixed in 43 days Boston tows on the spot!

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Unread 11-15-2011, 01:12 PM   #2
Rubi4MyMrs
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I’m not an expert on this or anything but I have a couple ideas to try. I think the code is telling you there is a communication problem between the cluster & the PCM. It may be as simple as a bad connection at the connectors behind the cluster or maybe as bad as a bad PCM. Start with simple things first. Does the CEL light when you turn the key on? After you clear the codes (if any) does the display say “DONE”? Test the CEL by leaving the gas cap loose or off & starting the engine & see if it throws a code.

This will help determine if the basic system is working. Usually if you lose communication you will get a “no bus” in the display. I have no idea why their scanner is causing the code. You can also try the cluster actuator test. This is done by holding the odometer reset button down while turning the key on (no start) & releasing the button. That will start a series of functions & end with a failure code or a “no faults” message. You can find this procedure in the FSM in 8J INSTRUMENT CLUSTER section. If you don’t have the manual you can find a read only version here. http://www.jeep4x4center.com/knowled...ex.htm#service pick the TJ UNLIMITED option to get the ’03-’06 manual. Bring up the Instrument Cluster & go to page 10 & read from there.

The actual system diagnosis may need to be done with a DRB III scanner that the dealer & SOME independent shops have. I don’t think a standard OBD II scanner will do it for you.

In case you don’t know you find the codes by turning the key (without starting) on-off-on-off-on & reading the odometer display. Clear the codes by disconnecting the battery for a couple minutes.

I don’t see why the alarm would affect this but you could disconnect it from its power source to be sure.


If you find the cause, be sure to post results.
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Unread 11-15-2011, 01:18 PM   #3
Robert J. yates
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I've had that problem when trying to smog test my Jeep... I took it to another shop and and the problem went away.
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Unread 11-15-2011, 02:41 PM   #4
nyurdrms
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Last night I disconnected the battery for a half hour and used canned air on the PCM connectors. The doesn't come on at start up. In 4 years of ownership it only came on once when I had the gas cap off. So I know it works. It really does just come on when I go in for Inspection. I appreciate the input from you both - hoping the Robert is right and its the shop, not the Jeep. But if it is...I'll walk through your recommendations step by step.

Massachusetts requires 125 miles in between Failed Registration tests and re-applies. I've still got 100 miles to go, once done I'll roll it back up (the shop says they're replacing their equipment with new versions) and try it again.

I'll post back once done.
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Unread 11-15-2011, 03:11 PM   #5
Rubi4MyMrs
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Good that it worked then, I'm saying to test it now to make sure it is still OK. If not then you know you have more work to do before retesting.
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Unread 11-15-2011, 03:17 PM   #6
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It might sound strange, but when is the shop plugging in the diagnostic equipment (plugging into the OBDII port)?

Do they plug it in and then start the Jeep? Is the Jeep running and then they plug it in?

If possible, next time, make sure the Jeep is running, then plug in the diagnostic equipment. I had that code appear on another car, and that always prevented the code from appearing. But if the car wasn't running, and then I plugged in a scanner, the code always appeared.
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Unread 11-16-2011, 07:25 AM   #7
nyurdrms
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Hi again,

As previously mentioned, the battery was disconnected, cleaned and reinstalled. The PCM connectors were removed, blown with canned air and reinstalled. I had a JEGS power programmer installed (which has passed inspected twice already) so I also removed that.

As the Check Engine Light (CEL) illuminates in the "On" position I know its functional but as it only appears when running upon hook-up at the Inspection shop I purposely left the Gas Cap off this morning when I filled up. I drove it an additional 6 miles to work but the CEL did not come on. But, as I filled the tank completely I don't feel there isn't enough of a variance between the fuel and pressure to get it to register with the CEL just yet.

Getting to work I ran the key-test (on/off, on/off, on, within 5 seconds) and it immediately registered "done".

If you all agree that the Gas Cap would have caused the CEL to come on had I filled 1/2 tank, then it sounds like she should pass Inspection the next time I run it through.

Any thoughts? And thanks again for the help! This forum (and your replies) have saved me thousands in the past. I'll post a picture if I have one available here on the office system.
2010-02-21-16.06.32.jpg   2010-02-21-16.05.48.jpg  
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Unread 11-16-2011, 08:45 AM   #8
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Quote:
Originally Posted by nyurdrms

If you all agree that the Gas Cap would have caused the CEL to come on had I filled 1/2 tank, then it sounds like she should pass Inspection the next time I run it through.

Any thoughts?
I think the CEL should have lit with the gas cap loose no matter how much fuel was in the tank; the point of leaving the cap off was to test to see if your system is working correctly and it isn't.
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Unread 11-16-2011, 09:04 AM   #9
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Quote:
Originally Posted by flying_bosun View Post
I think the CEL should have lit with the gas cap loose no matter how much fuel was in the tank; the point of leaving the cap off was to test to see if your system is working correctly and it isn't.
The loose gas cap is only detected when the system does a leak test. I believe it only does that when the fuel gauge registers above 1/4 full and below 3/4 full. I'm a bit fuzzy on the exact parameters, but it's my understanding that it won't register a gross evap leak instantly with the cap off.
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Unread 11-16-2011, 10:54 AM   #10
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Quote:
Originally Posted by mrblaine View Post
The loose gas cap is only detected when the system does a leak test. I believe it only does that when the fuel gauge registers above 1/4 full and below 3/4 full. I'm a bit fuzzy on the exact parameters, but it's my understanding that it won't register a gross evap leak instantly with the cap off.
Thats correct the PCM would have to go into test mode open loop test. And the timing on that I'm not sure when the engine is up to normal temps. But cold fresh start it will go into open loop in most cases.
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Unread 11-16-2011, 11:13 AM   #11
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Quote:
Originally Posted by mrblaine View Post
The loose gas cap is only detected when the system does a leak test. I believe it only does that when the fuel gauge registers above 1/4 full and below 3/4 full. I'm a bit fuzzy on the exact parameters, but it's my understanding that it won't register a gross evap leak instantly with the cap off.
Just about the only thing I dislike more than being mistaken is giving bad advice. Thanks for correcting my error.

Quote:
Originally Posted by JWebber View Post
Thats correct the PCM would have to go into test mode open loop test. And the timing on that I'm not sure when the engine is up to normal temps. But cold fresh start it will go into open loop in most cases.
Would dis- and reconnecting the battery force a test loop initiation even with a warm engine?
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Unread 11-16-2011, 12:16 PM   #12
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I'll start it tomorrow morning with the Gas Cap off and see if it registers cold-engine. I've driven 15 miles since filling up this morning (engine at normal temp) and it has not illuminated the CEL.

I'll also swing by AutoZone tonight and have them plug in to see if its reading the Gas Cap and not illuminating the light, and see if the U0155 message (Lost Cluster Comms) is still here and also not illuminating the light.

What I don't get...say that both codes are there when I check it later...why does it illuminate @ inspection?

As I said, it instantly reads "done" when I check for codes. It's been 35-40 miles since they cleared off codes. It surely would have reset everything by now and be showing codes if there were some? Right?

This has got to be the most annoying Code problem I've ever had. And every Jeep I've had has given me reading issues....
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Unread 11-16-2011, 01:19 PM   #13
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I'd just want to see if it throws the code you plug in another reader. It only checks the evap system when the tank is lower the 3/4 and the engine cold. You'll have to put few more miles on it.
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Unread 11-28-2011, 11:04 AM   #14
nyurdrms
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Quote:
Originally Posted by Shakey View Post
It might sound strange, but when is the shop plugging in the diagnostic equipment (plugging into the OBDII port)?

Do they plug it in and then start the Jeep? Is the Jeep running and then they plug it in?

If possible, next time, make sure the Jeep is running, then plug in the diagnostic equipment. I had that code appear on another car, and that always prevented the code from appearing. But if the car wasn't running, and then I plugged in a scanner, the code always appeared.

Hard to believe but this suggestion solved the mystery U0155 code. The Jeep failed inspection once again after I had cleaned the ECU and dash wires. We cleared the codes, drove it 50 miles (so it would reset) and tried it again at the same place as I had been testing it. But, we ran the Jeep and then plugged in the equipment. She passed with no problems. Odd huh? Either way, thanks so much for the input from everyone! With my luck I'll be touching this thread again in 12 months...
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