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Discussion Starter #21
Thanks for all the feedback. Looks like possibly the driver's MICU may be the place to start. You would not happen to know the part number for that by any chance? Just curious.
 

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Some more thinking out loud here...the more I think about it, if the driver's MICU doesn't know the doors are locked it would make sense that the tailgate wouldn't be locked because the tailgate control unit doesn't receive a lock signal, through the rear junction box, from the driver's MICU. If the MICU doesn't know the doors are locked the speed signal might continue to try and lock the doors when the speed is over 9 mph.

I think the "lock" signal is not making it's way out of the driver's MICU. I realized that would be something to try and look at with a scan tool while looking at Body Electrical. So, I broke out the Foxwell NT510 again and I went into Body Electrical >Door Locks and looked at some data on my van. You can see all the individual door lock positions but also a Door Lock command and Door Unlock command. When I lock my doors I see the Door Lock command go from OFF to ON momentarily then back to OFF. When I unlock I see the Door Unlock command go from OFF to ON momentarily and back to OFF. So, it's sending a momentary lock or unlock command out to all the modules it's communicating with. I'd be curious if all those lock commands are working properly on your van. Again, a scan tool is vital here.
 

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It would also make sense that when you disconnect the battery that the modules probably default to having seen a lock signal last and that's why the tailgate seems to be locked after that. If an unlock signal goes out via key fob or unlock button but a lock signal doesn't then the modules on that communication line would be stuck in the unlock status. This is all just my theory from studying the diagrams and analyzing the scan data.

The next hurdle would be verifying with scan data that a lock signal is being generated or not, and if not, figuring out why.
 

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I believe the part number is 38200-SHJ-S62. However, we don't know it's at fault yet. They are nearly $300. You might be able to find a used one at a wrecking yard and try it to see but I'd inspect the front and back of it first before spending any money. Look for signs of wiring damage or water damage in the connectors. I'd also want to see what the scan data shows on the lock/unlock commands. If you can see the commands on the scan tool that means they are being generated, just not being received by the tailgate control unit so that would be the next thing to figure out. If it's not being generated then you'd still have to figure out why. I know you said all the other doors lock and unlock but are they reporting that they are locked and unlocked? Lots to diagnose, before throwing parts yet.
 

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Discussion Starter #25
Thank you again. I do not mind picking up a scan tool as it would definitely help with this issue. Is the Foxwell one you would recommend?
 

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Yeah, I have more advanced tools than that one but it's a pretty good tool and quite a few here have purchased it. The Foxwell NT510 has bidirectional capabilities so you can activate outputs like AC compressor, fans, windows, doors, etc. It's most of what comes on a professional level scan tool. You can purchase it with Honda software and can add other manufacturers for around $60 each up to 5 manufacturers. It's a great tool for the price. You can pick it up on Amazon. That's where I got mine a few years ago.
 

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Discussion Starter #27
I have been meaning to order one for a while, so I put one on order today. Will probably be Friday before I get the tool and can start diagnosing this again. Will let you know what I have then.

Just curious what function under "body" did you use to see these readouts? Will save me time. Thanks.

It could be difficult to diagnose this without a scan tool that can read the switch inputs from the latch (tailgate closer unit.) I went out and looked at mine with my Foxwell NT510 tool. When closed all the switches are in the OFF position with exception of the Ratchet switch, which says ON when closed.

Tailgate close:
Neutral switch: Off
Release switch: Off
Full latch switch: Off
Ratchet switch: On
Half latch switch: Off

Tailgate open:
Neutral switch: Off
Release switch: On
Full latch switch: On
Ratchet switch: Off
Half latch switch: On
 

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Plug in tool and let it boot. Click on Honda icon (this tool comes preloaded with various individual manufacturers so make sure you get one with Honda preloaded.) Click on USA model. It will then ask you what module you want to scan. Choose Body Electrical. Then choose Door Locks. Then look at Live Data. It will give you options of what data PIDs you want to view. I just chose "select all" and then "View Data." You can look at codes and see if there is anything in there that is helpful but mine had a bunch of communication codes in there when I'm having no issues with my van so wasn't too helpful. Just view the live data for the door lock system.

If you want to view the power tailgate switch data, instead of choosing Door Locks, just choose Power Tailgate and go to the Live Data for that module. My guess is those are fine since that's what I'm guessing the dealer changed already. They likely could have viewed that data and realized all those switches were working and not replaced that latch but they are parts changers, not diagnosticians. Sad but it's the reality of dealer techs. Often they are the guys fresh out of tech school.
 

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Discussion Starter #29
Thanks. That sounds easy enough. Once the tool arrives, I will hook it up and grab some screen shots of the data at various intervals or actions.
 

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We indirectly verified the full latch switch is working even without the scan tool. I'd focus on the door lock info. That's where I think the problem lies. I think there is no door lock command being sent on the B-CAN line.
 

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Discussion Starter #31
We indirectly verified the full latch switch is working even without the scan tool. I'd focus on the door lock info. That's where I think the problem lies. I think there is no door lock command being sent on the B-CAN line.
Received the scan tool. It's a NT530, so took me just a minute to navigate. My tailgate open/close data was the same as you posted. With respect to the door lock data, all the driver, passenger, and sliding door data seem to operate as expected. For the Tailgate, I only see the "Tailgate Switch" and "Tailgate Knob Switch (UNLOCK)" When the tailgate is opened, the Tailgate switch is ON and when closed, OFF. The Tailgate Knob Switch (UNLOCK) never changes, it always reads OFF. Open the Tailgate from inside switch, key fob, or outside latch and it still reads OFF. Operate any lock mechanism in either LOCK or UNLOCK and it still reads OFF. According to the HELP function, that signal is received from the rear junction box. Any ideas what to check next? Thanks.
 

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There are individual door lock/unlock status pids. Your particular vehicle has no tailgate lock so it makes sense that would not show any changes. However, in the list of live data under Body Electrical >Door Lock there is a generic "door lock" and "door unlock" status. They normally read OFF and when you lock or unlock the appropriate status will momentarily change to ON then back to OFF. Did you check those? I was thinking it's possible you will see the "door unlock" status change to ON and then off when you hit the unlock button but the "door lock" stays at OFF when you hit the lock button and never sends an ON command.
 

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Discussion Starter #33
Yes, I did verify those commands and they work as I think they should. LOCK goes ON when initiated, then back to OFF. UNLOCK goes ON when initiated, then back to OFF. I snapped a picture with my phone if it would be helpful to attach. Of course, the scan tool does seem to freeze after 3-4 initiation, so you have to wait for it to reboot. But, otherwise, they seem very consistent.
 

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So that would seem to indicate the driver's MICU is communicating with the rear MICU with regards to the lock/unlock signals. It makes me suspect the tailgate control unit but that wouldn't explain the locking/unlocking while driving. It's uncommon for modules to fail and usually more likely that there is either some corrosion somewhere or a broken wire.

Again, the only way the tailgate locks is that something (presumably the lock signal) tells the power tailgate control unit not to open when any of the switches are pressed. So, that means that whatever signal does that is not making it to the tailgate control unit or the tailgate control unit is not doing what it's supposed to. It might be worth removing the D pillar trim on the driver's side and inspecting the tailgate control unit and it's connector for any visible signs of issues like moisture or wiring damage. I'm kind of running out of ideas.
 

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It might be worth running an all systems scan and get codes out of every module. There may be something that gives us some more clues there. Sometimes modules will "tell on" other modules.
 

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Rereading through the thread. Can you elaborate on what the car was doing with the locks, and what the locks were actually doing, when you were driving? Did all the doors actually lock when you start to drive but then continue to lock or did they unlock and lock? I know you disabled this system and solved that annoyance but it could be very helpful in determining the cause of this. It's very likely it's all related.
 

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Discussion Starter #37
All the doors will lock with exception of the Tailgate. When you slowed down around 10 mph it would sound like the locks were trying to actuate, although the doors were already locked. Honestly, I rarely noticed, the actuation noise was quieter, but my wife has exceptional hearing and notices everything. HaHa! They would not UNLOCK, just try to LOCK. I will take a look at the tailgate control unit on Friday, as I am at work tomorrow. When you say run all scan codes and get codes out of all modules, which specifically should I be looking for? Is there a way to save, then read all the codes on a printout? The scan tool is a bit cumbersome for too many codes. Thanks again.
 

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I think there is a Save option but I've not used it. The option to see all the codes in all modules is the Auto Scan menu.

Another thing I'd try is under Body Electrical >Security. Select all the items and view all the Security inputs. Sit inside the car and lock it and make sure all the data pid status in that list make sense. I'm thinking since the horn doesn't sound when you lock/arm the vehicle that maybe one of those inputs is not correct and will give us some direction.
 

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Discussion Starter #39
May have found the culprit this evening. Ran the security codes. Everything seems to work fine with exception of .... Driver's Door Lock Knob. UNLOCK always remains ON and LOCK always remains OFF even though it does travel up and down. All others rotate ON and OFF as they are locked and unlocked. The other oddity is the Driver's Door Key Cylinder Switch will not LOCK. I can use the key to UNLOCK, but it will not turn to the LOCK position. When you use to the key to UNLOCK, the switch will shift from OFF to ON. The key will not physically roll to the LOCK position, although the manual does say you can LOCK and UNLOCK with the Key. Since the system would never receive a lock signal from the Door Lock Knob, it is my thought that is why the system will not arm and the rear Tailgate will not (lock) deactivate. Any thoughts?

If that is the case, I imagine I should pull off the driver's door panel and look at those mechanisms. So, how hard is it to change out the Door Lock Knob? Can I change the Door Key Cylinder mechanism, or would it need to be rekeyed? What would you recommend?
 

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Bingo! You found it. You'd never have found that without the scan tool, either! Other than the fact that the key doesn't lock the door and I can't even remember the last time I put my key in the door.

So, the key physically won't rotate to the lock position? It sounds like something is mechanically stuck either in the door latch mechanism or the lock tumbler. My guess is something in the latch since the door lock knob status never changes with locking and unlocking the doors. Yes, I'd say it's time to break into the door and see what's going on.
 
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