I had a failing rear wiper motor, so I replaced it. I started the TB up and ran through all of the switch settings and the rear wiper worked like a charm. However, after turning the TB off and letting it sit for a few minutes, when I opend up the driver door, the rear wiper made one swipe. I let it sit a few more minutes, and opened up the passenger door and the wiper made another swipe. I was able to replicate this random swipe with the TB off by opening the rear hatch, and even the liftgate glass (which was quite dangerous as it almost swiped my head). It seems like when it sits for a few minutes, any electrical current makes the rear wiper make one swipe. I removed the fuse for now, but am at a loss for what is going on. Any suggestions? Thanks in advance.
SOLVED! Rear wiper random swipes when TB is off and key removed
- Thread starter timmanz
- Start date
Mooseman
Moderator
The rear wiper motor is directly controlled by the liftgate module which received a signal from the BCM which receives the commanded wiper speed. Sounds like the LGM is sending erroneous signals to the wiper motor as it's being used via opening the liftgate.
Are there other liftgate functions that aren't working right like the key fob or locking mechanism?
quote: "had a failing rear wiper motor, so I replaced it." what does this mean... what was it doing? It appears that your "home position" is not being detected.... hence the question. check the wiring going towards the lgm.
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No, everything else seems to be working. The doors lock, the keyfob works, the wipers work at the correct speed and intermittence when I have the switch turned on. It is just that phantom swipe when the TB is off that is the issue.
The motor had completely stopped working. I bought a replacement motor and replaced it. Everything seems to work such as keyfob, locks, and the wiper works correctly when the switch is on. It is that phantom swipe after the car is off that is the issue. It will do this up to at least 30 minutes after I turn off the TB.
Mooseman
Moderator
Now I do know that the wiper will park itself if left on when you shut off the truck. It could do one last swipe before parking itself. Maybe you got a bad new motor and makes the LGM think it's not parked. Was it a new Dorman by any chance? Their reputation for anything electrical is dubious at best. For this, I would have gone with a used one.
It parks itself when the vehicle is turned off. Then, after it sits for a while, if I open a door or the rear lift glass it will swipe again. If it sits for a while again, it will do the same thing. I can replicate this multiple times with the TB off, so it is not a one time deal. Unfortunately, I bought a knockoff brand from eBay. Could that be the issue?
Mooseman
Moderator
Yes! It could be interpreting different signals as a "wipe" signal. The motor is always powered. Normally, the LGM sends different signals so the motor might be interpreting them as a Wipe and Park signal. It seems to take any signal from LGM. It's also possible that the LGM is sending bogus signals to the motor. I have no idea as to what type of signals it sends.
Without proper equipment, you can't check the LGM signals. Maybe @TJBaker57 can assist there.
In prior posts concerning Electrical Problems related to either the LGM OR the Wipers and ancillary Lift Gate issues... THIS has been brought up by @Mooseman as yet another concern:
The Wires passing from the Body LGM Harness through the Upper Roof Cavity and into the Lift Gate itself will WORK HARDEN and fracture; either completely ...or hidden and separate within the thin Plastic Insulation and wreak its havoc on anything dependent upon their proper circuits AND their Class 2 Communications.
ANY damaged or inoperative Class 2 Network Module can have a telling, negative affect upon the entire Class 2 Network.
gmtnation.com
gmtnation.com
If you need to Probe the Wiring for Continuity between the Lift Gate Module and its "extremities" and its Plug-In Connector to figure out What goes to Where... THIS Diagram may prove useful:
The Wires passing from the Body LGM Harness through the Upper Roof Cavity and into the Lift Gate itself will WORK HARDEN and fracture; either completely ...or hidden and separate within the thin Plastic Insulation and wreak its havoc on anything dependent upon their proper circuits AND their Class 2 Communications.
ANY damaged or inoperative Class 2 Network Module can have a telling, negative affect upon the entire Class 2 Network.
rear wiper phantom sweep
Have a '06 TB Ext that has a weird problem. The rear wiper will do a phantom sweep engine off key out of the ignition. At first motor stopped, replaced it. Work for a day or two then stopped and the phantom sweeps started. Replaced the the LGM and programmed, wiper worked of several days then...
gmtnation.com
NEED HELP - Liftgate electrical problems
It all started with a defogger that did not work. Same thing happened on my 04, turned out to be a broken wire. Took a look but couldn't find anything. Didn't have time to mess with further. The next day I found that the rear wiper wasn't working either. Also the remote fob didn't seem to...
gmtnation.com
If you need to Probe the Wiring for Continuity between the Lift Gate Module and its "extremities" and its Plug-In Connector to figure out What goes to Where... THIS Diagram may prove useful:
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The weird thing is that everything works as normal when the vehicle is on. Then, if I turn the TB off and let it sit for 5+ minutes and then open any door, the rear wiper will swipe one time. Then, it has to sit for another 5+ minutes, and if I open any door, the liftgate, or the rear glass it will swipe one more time. It is not jsut opening one location that will cause this. Any door will do it. It will not do it back to back without sitting for a few minutes.
In some instances... having any Class 2 Network "Shorts to Ground" or "Shorts to Positive" happening INSIDE of certain Modules can stimulate the Network to "Wake Up" instead of staying asleep. The mere action of opening ANY Door can cause this to occur if the system has never actually gone completely "To Sleep" in the first place.
General Motors OBD2 Class 2 Networks function on what is called a "Star Topology" where ALL of the Modules are using One Single Wire actuated by using Pulse Width Modulations that will vary between 0 and 7 Volts DC. This the Weakness in the Single Network Wire Plan.
If any one or more of the Myriad Modules have broken or frayed wires that are being stimulated when they should NOT be Active... these kinds of phenomena can act like "The Ghosts in The Machine" as they interact with each other and exhibit these strange behaviors...even to the point of bringing down the entire Network.
Spend some time observing the investigation procedures being followed below in this very worthwhile "Primer on Class 2 Network Diagnostics" and you should be able to use Will Robinson's *** Approach in discovering exactly which Module is the one actually giving you the trouble.
Please note that even though it presently manifests with the Windshield Washer Motor Odd ACTION here, it does NOT necessarily HAVE to be related directly with the Tailgate LGM Module... but it MIGHT be if you DO manage to PROVE it out in the following manner:
*** Will learned HOW to Solve This Problem courtesy the Instructions and the Training he received from Keith DeFazio from "New Level Auto".
General Motors OBD2 Class 2 Networks function on what is called a "Star Topology" where ALL of the Modules are using One Single Wire actuated by using Pulse Width Modulations that will vary between 0 and 7 Volts DC. This the Weakness in the Single Network Wire Plan.
If any one or more of the Myriad Modules have broken or frayed wires that are being stimulated when they should NOT be Active... these kinds of phenomena can act like "The Ghosts in The Machine" as they interact with each other and exhibit these strange behaviors...even to the point of bringing down the entire Network.
Spend some time observing the investigation procedures being followed below in this very worthwhile "Primer on Class 2 Network Diagnostics" and you should be able to use Will Robinson's *** Approach in discovering exactly which Module is the one actually giving you the trouble.
Please note that even though it presently manifests with the Windshield Washer Motor Odd ACTION here, it does NOT necessarily HAVE to be related directly with the Tailgate LGM Module... but it MIGHT be if you DO manage to PROVE it out in the following manner:
*** Will learned HOW to Solve This Problem courtesy the Instructions and the Training he received from Keith DeFazio from "New Level Auto".
Well, I figured out what my problem was. I sent the wiper motor back and got a replacement. That one is working fine. Go figure.
Mooseman
Moderator
It was an eBay off-brand from Total Auto Parts. I will say they replaced my bad motor with no questions asked, so I was very happy about that.