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2008 Jeep Patriot Limited. 2.4L CVT
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Discussion Starter #1
Hoping someone might be able to help me solve this mystery, my mechanic and I are struggling to track down the issue. I've seen a lot of similar problems posted but can't find anything with the same circumstances as me or a solution I haven't tried, please link if I've missed something!

Basically, I've been experiencing random stalls and inability to start that I suspect are being caused by a sudden loss of power to the ECU. This has been an on and off issue for a few months. It will happen once or a couple days back-to-back, then I'll have no issues for weeks. Yesterday it stalled 5 or 6 times while idling; first couple were in park outside my house while I was getting ready to leave, then another 3 or 4 times when I was in a drive-thru a few mins from my house. Prior to that my last issue was over 2 weeks ago (usually drive every 1-3 days)

Stalls: This happens mostly while idling both in park and drive, but it has happened once while I was driving slowly (around 30km/h). Basically out of nowhere the engine will shut off and I'll get a chime (typical lights come on as when the engine is off while the key is in the run position). I can usually restart the engine right away (after shifting into neutral of course), but sometimes I will have starting issues as I detail below. If I restart right away, sometimes the ESP and traction control warning lights come on. First time this happened it was driving in limp mode. Its happened once or twice since then and I just do a full power cycle (remove the key, open the door, wait a few seconds, the restart the engine) and it drives normally with no warning lights.

Starting Issues: Again, this usually is pretty random, but I have generally had it happen after my pat has sat overnight or for a day or two. I'll turn the key and all the accessories work, dash lights come on, etc. but the starter wont crank. Doesn't even try to turn over. I'll just try a few times and have gotten it to work with eventually every time with some persistence. I once was able to get it to work by literally shaking the jeep side to side by shifting in my seat.

I suspect a power supply issue somewhere: my battery is barely 3 months old so I know it isn't that. At first I thought the starter might be on its way out, but it doesn't struggle to start at all when it does work. That, and once the stalls started happening I ruled out an issue with the starter. I have cleaned up all of the easily accessible ground connections but it hasn't solved the issue (not that any of them were corroded, but I pulled them off and cleaned up the metal anyway).

I am convinced the ECU is losing power somehow as when the stall or starting issue happens it clears any engine codes (I have two permanent codes that keep the check engine lights on, details below, but they are cleared after restarting the engine). That, and after a stall the traction control and ESP lights come on. When this happens if I fully power off (that is, remove the key and open the door) the warning lights go off and it starts up just like normal.

Details:
2008 Patriot Limited
2.4L engine
CVT Transmission
254,000km

Other Notes:
  • The first time the jeep went into limp mode I had 4 codes, P0700, U0100, and B2AAA twice, but haven't gotten any codes since
  • I am up to date on all my regular maintenance and have always taken good care of this
  • I'm the second owner and have had it for the past 90,000km (~5 years)
  • I just replaced the spark plugs, air filter, and coolant (these issues were already happening when I did)
  • I generally don't tow anything, although I had a small trailer I took cross-country last summer. I have the tow kit though and it ran fine the whole way.
  • I occasionally get the sputtering acceleration issue other members have posted about, but its never been a major issue so I've just lived with it.
Known Issues:
  • Have had a code for the cat for quite some time (something along of the lines of running below efficiency threshold), my mechanic says maniverter is on its way out but since it drives fine I haven't bothered to do anything with it. That, and it would cost much more than the jeep is worth to fix it.
  • Have a code for fan 1 relay. The relay is corroded so its not getting power. It's on my list to fix, but its not that warm and the temps are always normal so its not a priority atm.
Please Help! I've been fortunate that I've never stalled in traffic, but I don't want to leave this to chance since it could cause an accident if I stall in traffic or on the highway. Has anyone had this to them? Anyone familiar with power issues related to the ECU? Any ideas on what I should try? Thanks in advance!
 

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First thing I'd do is check all of your grounds again. Especially the ones where several wires crimp into one ring terminal. There are quite a few posts on here that show where these are, and I'm reasonably sure that Sandstone or Ignatz will post their locations here... they're pretty awesome like that.

Also, there is a relay box in the front, between and below the battery & left headlight. Pop off the cover and pull the relays one at a time to check on their condition as well as the condition of the terminals that they plug into. It's quite common for the wires/relays there to corrode, which can kill power to the ECU. That happened to me a few weeks ago... about a dozen wires in mine corroded, taking out 3 relays. The typical fix for that is to bypass the box for the affected relays and just wire them up beside the box, because that box isn't a seperate part... it's integral to the wire harness, which would be super expensive to replace.
 

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I'm thinking maybe a ground, a bad connection to the battery, or a bad connection at the mains relay in the relay box.

If the main relay loses connection power will also be lost to the injectors (fuse 26), ignition coils (fuse 23), and PCM (fuse 32). You could test it by pulling fuse 18, replacing it and seeing if that recreates the problem.

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91768



Also, as mr_et2 mentioned, the grounds can corrode up inside the crimp on the ring lug under the insulation where you can't see it.

G110
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G111, G112
91769
 

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2008 Jeep Patriot Limited. 2.4L CVT
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Discussion Starter #4
Thanks to you both!

I'll go back around and take a closer look at all the ground connections this weekend and see if I can find anything there. Good to know the relay box could cause something like this too - last I checked it was just the one cooling fan relay that had corroded out but I didn't check the wires, just pulled the relays to look at them. I'll have a closer look there too.

Your comment on the battery connection got me thinking Sandstone, and I just went out and rechecked all the basic stuff. I was checking the negative terminal connection and it seemed tight at first, but if I really put some work into it I am able to rotate it slightly - I don't think that's supposed to happen so that might be the issue too.

I'm headed to the junkyard later today anyway so I'll see if I can track down connector for the battery wire and a couple relays in good condition, then go to work on checking all the grounds. I'll report back on what I find! Thanks again for your help.
 

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2008 Jeep Patriot Limited. 2.4L CVT
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Discussion Starter #6
Alright so I think I may have stumbled across the problem, fingers crossed!

It wasn't the battery connection: I removed the loose connection, filed down the pieces a bit and replaced the screw that tightens it down so I was sure I was getting a tight fit. Even after that it stalled on me while I was idling and getting the gps setup.

While I was sitting there I randomly remembered an article or something I read quite a while ago about a guy who had a wireless code reader plugged in to his OBDII port that was damaged over time and causing all sorts of electrical issues (if memory serves there were exposed wires on the reader that were shorting out). I have one of those wireless readers as well and had left it plugged in for the past while and got to thinking I may be having a similar issue.

While there is no visible damage to the reader, I unplugged it anyway and haven't had any issues the past couple days! I'm going to give it a couple weeks before I assume the issue is solved for good, but here's hoping that's all it is. I haven't gone through the ground connections again yet, so we'll find out with time if the reader was the issue or not. I'll update in a couple weeks!
 

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That's a new one on me! I never would have thought of that, and I have a bluetooth code reader that's always plugged into mine. Hopefully it won't give me issues.
 

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2008 Jeep Patriot Limited. 2.4L CVT
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Discussion Starter #8
Alright, I have some good and bad news. Bad news is that the code reader was not the issue. Was trouble-free for a couple days but I couldn't get it to start at all this morning. The good news is I found another potential source - the relay box.

When I was trying to start this am it was the same usual issue - accessories all come on and work fine, but I get absolutely nothing from the starter when I try to crank the engine. I read the codes and the only one was U0100 (Lost Communication With ECM/PCM 'A'). Even my other pre-existing codes were gone and I didn't clear them. I tried clearing the code and it wouldn't go away so I suspect the communication fault was persisting.

After some further googling, I found this video about a compass with very similar issues:
I know my cooling fan 1 relay is corroded out identically to the ones the guy shows in the video, but the rest look okay (one had some corrosion starting to form but it wasn't all that bad - I cleaned it up until I could track down replacements, haven't found any yet so I may have to bite the bullet and go to the dealer). My suspicion is that either a) one or more of the wires feeding the box have corroded, or b) another relay has gone bad (perhaps the main engine relay as he mentions in the video). It has been raining non-stop all week so maybe the added moisture sealed it's fate - lol.

It'll probably be a bit before I get to this repair since the forecast isn't looking great, but here's my plan. I'm thinking of moving that entire box further up in the engine bay, maybe mounting it beside the relays or something - has anyone attempted this before? I'm thinking I'll need to splice in new wires to make them long enough to do that - does anyone know what gauge of wire I should purchase. Is this even a good idea or should I just splice in the individual relays?

I did make a trip to the local junk yard and had no luck finding relays as all the patriots and compasses had the entire box removed, so there isn't any chance of finding a new one. By moving the existing box up I'm hoping to prevent any water penetration in the future (seems like its in an awfully stupid place currently). I plan to clean out any corrosion and move relays to the empty ports for any that are corroded too badly to clean.
 

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Discussion Starter #9
Just wanted to update, I've solved the problem! Turns out it was an issue in the relay box.

I knew I had an existing issue with the cooling fan 1 relay having corroded out, but I found that the wire that had corroded also connects to the other relays (i'll put pictures below). When I make my way to the dealer to get a new relay I'm going re-wire it to one of the spare ports, but for the time being I just soldered the two wires together and the starting/stalling issues have gone away!

Here's my fix:
91831

Here's the relay box with the cooling fan 1 relay removed (top-right spot), you can see the green corrosion in the one corner there.

91832

This is the bottom side of the relay box. These two wires I have twisted together were both feeding into the spot that was corroded in the previous image. Turns out that not having these connected is enough to prevent the engine from running and trip those communication codes. I pulled them out, cut out the corrosion, then stripped the wires and twisted them together as shown and she started right up.

91833

You can see my temporary fix here. I've soldered those wires together and taped them up, then I pushed them up into one of the ports to keep them out of the way. The jeep runs just fine like this, but one of the cooling fans doesn't work so I'll be watching temps.

All the other connections are good, so I plan to rewire a new relay into the middle-left port (shown in the first picture). It was easy enough to pull the connections out, they all have little tabs holding them in. To get them out, start by removing all the relays then remove the white tray (there are 4 tabs, one in each corner, holding it on). Once that's off, you can access the tabs holding the connectors in with a small screw driver. Push the tabs back with a screwdriver then pull the wires out the back. They're in there snug, but shouldn't require much force to remove so be careful not to break them. Once you have them out you can snap them into their equivalent spots in the new port. I bought a new connector to replace the corroded one that should fit so I'll wire that up once I have a new relay.

As a preventative measure I also put a coat of dielectric grease on all the connections - hopefully that will prevent any others from corroding out in the future! Hopefully this will help someone who runs into a similar issue (y)
 

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