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Old 06-25-2012, 11:48 AM   #1 (permalink)
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Default 2006 Outback Cruise Control problems

Hello all,

looking for advice/solutions regarding a recurrent problem with the cruise control on my Outback. It's a 2006 Outback, 2.5i Limited, auto transmission, ~83k miles now. The cruise has acted intermittently for some time now, but has worsened in its symptoms/severity lately. Here are the relevant details:

Cruise system- This light always comes on when activated, but will sometimes shut itself off, either when under cruise control or not

Set/coast- the majority of times now, the set button will not activate the cruise control. This practically never works immediately after turning on the cruise, but after some minutes it will eventually sometimes come on. When this switch actuall does something, at times, it acts correctly as it should- i.e., setting the speed and/or coasting. At other times, this setting will actually act to accelerate the speed, like the resume/accel switch normally does. When this happens, neither the resume switch or the cancel switch works, and I either have to deactivate via brake, or shut the entire cruise system off

Resume/accel- sometimes works normally (when the whole system is working normally), and sometimes does not work at all. When it doesn't work, then the "Set" setting is acting as described above (either not working at all, or acting as the "Resume" setting).

Cancel- sometimes works normally (when the whole system is working normally), and sometimes does not work at all. When it doesn't work, then the "Set" setting is acting as described above (either not working at all, or acting as the "Resume" setting).

So, in short, the "Set" setting dictates the cruise behavior with 3 conditions: 1) Does not work at all, 2) Works, but the "Set" setting acts abnormally as the resume/accel setting, 3) Works normally, in which case the whole system works normally. The most common frequency of the conditions are listed in order here. The last condition, 4) Periodically the entire cruise system will shut itself off (this seems to be independent of the "Set" being activated, or whether it's actually currently on cruise control or not).

As I mentioned before, this problem has worsened over time. I have notified Subaru about this problem in the past, and again more recently since the "Set" setting started acting as an accelerator. This really alarmed me and seemed like a safety issue to me, and something Subaru should cover. I haven't pressed this with them yet, as I was hoping to get some feedback of expertise/similar experiences here, to make sure I'm not unreasonable with this expectation.

With the symptoms above, it seems most likely to be an ECU issue, as it's hard to imagine a switch/connection causing this type of issue, though I suppose it's possible a bad steering column switch/connector could behave this way?

Your thoughts/ideas on how to proceed are much appreciated!

P.S.- I hope I chose the right forum for this thread. Let me know if the Models>Gen 3 forum or some other is the more appropriate place. Thanks!
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Old 06-25-2012, 11:57 AM   #2 (permalink)
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To me it seems that you have a bad connection in the wiring. If the wires are frayed + touching for resume/accel and the set function, you could get the results you are seeing. I would find it hard to believe that the ECU is getting worse over time when no other conditions are changing.
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Old 06-25-2012, 01:05 PM   #3 (permalink)
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Quote:
Originally Posted by Kaarmaa View Post
To me it seems that you have a bad connection in the wiring. If the wires are frayed + touching for resume/accel and the set function, you could get the results you are seeing. I would find it hard to believe that the ECU is getting worse over time when no other conditions are changing.

I suppose it's possible since they're all on the same switch lever and presumably all pass through the roll connnector in close proximity, but I have to say that this seems unlikely to me, given the range of behavoirs (set, resume, cancel, and even the cruise system activation all being affected) . I can see bad connections on a couple of wires, but not all of them, unless it's a bad ground or something, which I suppose could confuse all of the settings.

In my summary, I should have added the 4th condition which seems to be independent of the "Set" being activated, and that is periodically the entire cruise system will shut itself off. Will edit that in now.

Thx for your input!
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Old 06-25-2012, 02:46 PM   #4 (permalink)
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Disconnect the neg. cable at the battery for 5 minutes-reconnect to re-boot the ECU.
If that doesn't work, disconnect BOTH pos and neg and touch the connectors together away from the batt terminals.
This worked on my '06 and my Passat W8.
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Old 06-25-2012, 03:09 PM   #5 (permalink)
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Although there's four switches, (ON/OFF, Cancel, set/coast, and resume/accelerate), the overall control of the system is effected by only three wires from the lever through the roll connector, one of which is a ground common to all four, and another is exclusively for the ON/OFF function (push button at the end of the control). (See attached diagram.)

The remaining three switches, which are the ones that are showing the most related symptoms, use the same two wires (the third wire, and ground).

Set/speed control is effected by closing one of the remaining three switches, which applies a different resistance ranging from zero (for Cancel) to something less than when all switches are open (the total of the three resistors in the diagram) across the two wires. The ECM identifies which switch/command is being used according to the level of the resistance.

I wouldn't discount a problem in the roll connector (not unknown), or in the cruise control switch assembly itself. In the case of the switch, bad contacts, and contacts that don't "break" properly (due, in some cases, to protective grease that has changed characteristics -- seen often in the turn signal switch), could lead to the problems you have described.

EDIT: Codger's idea to reset the ECU is also something to try.
Attached Thumbnails
2006 Outback Cruise Control problems-cc.jpg  

Last edited by plain OM; 06-25-2012 at 03:11 PM. Reason: add edit
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Old 06-25-2012, 11:19 PM   #6 (permalink)
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Thanks for the suggestions guys, and the very useful diagram. I tried Codger's suggestion of resetting the ECU, but no such luck there.

I guess the next thing to look at is the switch lever that has all the CC functions on it. How difficult is that to troubleshoot, and what's the procedure?

Let's assume the switch lever is appropriately switching in the correct resistance values. Then would the next possibilities be 1) The roll connector, or 2) the ECM? Does ECM= part of the ECU, or there's a separate module (Electronic Cruise Module?) ?

I guess the ECM must also take into account the current speed, and from this (and the switch settings/user activations) send some feedback to a servo that controls the engine rpms? Could this servo also be a possibility? I was thinking due to the behavoir that this didn't seem like a likely suspect, but that's pure conjecture on my part since I don't really know how this operates. Any other ideas for likely possibilities?

Thanks again!
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Old 06-26-2012, 08:20 AM   #7 (permalink)
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After the switch assembly itself, the roll connector would be a good possibility, all the more so in view of the intermittent nature of the symptoms. As the steering wheel is turned, the roll connector' flat, wound, ribbon, which contains the wires for the cruise control (CC), horn etc winds and shifts, so a broken wire would likely change position and perhaps make and break contact at different times.

As others have noted, I also would doubt the Engine Control Module (ECM). On your 06, it's one single unit -- basically a small computer. The cruise control is but one function that the computer is charged with (similar to a desktop having a number of different programs it can run).

Your 06 uses a "drive-by-wire" speed control system. Whether driving manually or using CC, the position of electrically-controlled throttle on the engine itself is being set by signals from the ECM.

The accelerator pedal is connected by wires (not mechanical linkage or cables) to the ECM, and depending on the pedal's position, the ECM translates the electrical signal from the pedal into a desired throttle position. It sends electrical signals to the throttle (actually a motor that controls the throttle plate position) and receives signals from the throttle as to where the plate is actually positioned. As the accelerator pedal position is changed, the ECM changes the position of the throttle.

When the CC is "set", the computer memorizes the car's speed at that moment (based on signals from the vehicle speed sensor), and then continues to control the throttle position to maintain that same vehicle speed without reference to the accelerator pedal (except if the pedal is pushed down beyond the point where the set speed is, at which time the pedal takes over and the car can be accelerated above the set speed).

There is no separate servo or actuator involved for the CC.

While it's possible that any computer can develop an internal glitch, whether in the software, or a mechanical fault (bad connection) that causes unusual symptoms, this is extremely rare, especially with the ECM. Granted, not impossible, but the very last on a list of possibilities.

Access to the CC switch requires removal of the steering wheel, which also means first taking out the driver's airbag (in the center of the steering wheel). I've attached a page from my 07 manual (should be the same for 06) about accessing the switch. There are some serious considerations to take into account when working around the airbag, and consequently, if you have any doubts, I'd suggest leaving this to a professional.

Otherwise, the resistance measurements indicated on the attached page would be a start. I wonder if, instead of removing the steering wheel, you could find connector B68. In this case, with the battery disconnected for a while, then B68 and ST1 can be separated, and resistance measurements made at ST1. (I would check the resistances repeatedly, i.e. pressing and releasing the switches many times, to be sure that "good" readings are always that way.) This would include, of course, the roll connector, so when making each measurement, I would also turn the wheel back and forth to cause change in the roll connector ribbon. (I believe B68/ST1 are somewhere along or next to the steering column, probably lower down. Those connectors have 8 pins. I've attached a diagram that shows the shape of the B68 connector and its pin numbers. This is looking at the end of the connector. There would be corresponding pins on the ST1 connector.)

Other notes:

The electronic systems on the car have some sophisticated on-board-diagnostics (OBD) that are continuously monitoring the functions. If there is an unusual fault, the OBD can, in many cases, note and subsequently identify the area the fault occurred. This applies also to the CC. If the CC light(s) are on, or flashing, when they should not be, then a fault has been detected. A dealer can use the Subaru Select Monitor to connect to the ECM and read the "code" that identifies the area causing the fault.

Also, the CC is linked with the brake (stop light switch) and with the transmission control switch (inhibitor switch), both of which have to be in certain positions (e.g. the stop light switch should be in the off position and the inhibitor switch should not be in P or N) in order for the CC to function (or, looking at it differently, both can turn off/disable the CC.) This could lead to strange problems if either switch is intermittently changing state while the CC is being used.
Attached Thumbnails
2006 Outback Cruise Control problems-connector.jpg  
Attached Files
File Type: pdf 231398 Cruise Control Command Switch 5.pdf (37.5 KB, 47 views)
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Old 06-26-2012, 10:51 AM   #8 (permalink)
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Hi plain OM,

that is some great information, Thank You very much for that and the explanations! Yes, if it comes to it, I don't think I'll be removing the steering wheel, as I don't care to mess around with the airbag.

Good idea regarding the B68/ST1 connectors. I'll try to see if I can locate those. So, the B68 and corresponding ST1 connectors have 8 connections. How do I know the pin numbers that correspond to the CC switch in the document you provided? Is it safe to assume that pins 1-3 map directly to the CC switch pin numbers?
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Old 06-26-2012, 12:26 PM   #9 (permalink)
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The CC document in post #7 is about the CC switch. It has three connections. The three wires from the switch join five others and end at ST1 (8 pins). The pins that correspond to each of the three CC switch pins (1-3) can be identified in the diagram attached to post #5. So:

CC Switch pin 1, goes to ST1 pin 1; CC switch pin 2 goes to ST1 pin 5; and, CC switch pin 3 goes to ST1 pin 4.

Note, that the diagram of B38 is looking at the "business end" of the connector. For ST1, which mates with thatt the pin locations will be a mirror image. So, for example, where pin 1 of B68 is at the upper left when looking straight on, pin 1 of ST1 will be at the upper right, again, when looking at the business end of the connector. (This is the way the diagrams show it. We have found anomalies, where sometimes the locations differ, or the wire color is not the same as the diagram, but that's rare. At least this gives you a starting point, and more than likely will be correct.)

As noted earlier, I'd disconnect the battery when pulling connectors as there are live circuits, even with the ignition key out.
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Old 06-26-2012, 12:53 PM   #10 (permalink)
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Ah, yes, I should have caught that, but failed to tie it back to post #5. Thanks for pointing that out and clarifying. If I can find the connector, I should have enough to go on here to identify if I have a problem in the switch/roll connector, and potentially isolate it down to which one.

Gotcha with the mirror image & will be sure to disconnect the battery. Probably won't get to this before the weekend, but will let you know what I find when I do.

Thx again!
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