Rear Wiper keeps going offline

[DIYguybob]

Hi to all, having a problem with the rear wiper. It works for a few weeks to a month and then stops working. Pull fuses, reinstall fuses, works for another 3 to 4 weeks and then stops working. Motor is new, replaced twice. Ground and power is good. No rust on my vehicle, so it's not a rust issue. It seems to me that the BCM sees something it doesn't like and shuts it down. Pulling the fuses, resets everything and the BCM allows it to work again. At least that's my guess.
Anyone have this issue and have some suggestions? Thanks in advance.

 

[Mooseman]

Check the glass hatch switch. I had that when the switch had fallen off and reporting the hatch as open. The interior lights would also come on if interior lights are not disabled. Also check the tailgate wires in the rubber boot.

 

[TJBaker57]

seems to me that the BCM sees something it doesn't like and shuts it down

FWIW, the BCM cannot see anything from the rear wiper. The rear wiper is wired to the LGM in the hatch.

The switch is wired to the BCM and the BCM sends an appropriate serial data message to the LGM which the LGM then acts upon to activate or deactivate the rear wiper.

The messaging between the two, BCM and LGM looks something like the following highlighted message frames...

 

[budwich]

Pull fuses, reinstall fuses

which fuse numbers are you pulling?

 

[budwich]

Ground and power is good.

where are you checking those?

 

[DIYguybob]

where are you checking those?

I pulled the rear hatch cover off and checked them at the motor.

 

[DIYguybob]

which fuse numbers are you pulling?

I have been pulling fuse 3 and relay 6. They are under the rear seat.

 

[DIYguybob]

Check the glass hatch switch. I had that when the switch had fallen off and reporting the hatch as open. The interior lights would also come on if interior lights are not disabled. Also check the tailgate wires in the rubber boot.

Can you show me what the switch looks like and where it is located? Txs

 

[budwich]

I have been pulling fuse 3 and relay 6. They are under the rear seat.

ok... thanks for the info. Does the system response change if you only pull one or the other (ie. pull one and then replace it... does the system now work?) Trying to isolate which item might be an issue. First guess would be the "relay". Have you tried another relay?

Another potential issue is "poor contact" at the relay box. If you notice the pins on the fuse and relay are pretty straight. Over time, the box receptacle "fingers" lose some of the ability to hold a good contact (ie. they are somewhat "spread" / weakened). People have found that putting a "slight twist" on the pins of fuses and relays helps with contact.... kind of making the pin "virtually wider".

ADDED: what year vehicle are you working... sorry if everyone knows but me...

ADDED: it appear that the fuse that are pulling, resets the LGM while the "relay" is for the rear wiper motor.... if I understand correctly from the drawings, its a breaker... maybe the breaker is no good and is sticking / not resetting.

ADDED: Of course, as others have pointed towards the LGM.... maybe you have some marginal wiring at the LGM resulting it being "confused" or the signal wire that it sends to the motor is marginal.

 

[Mooseman]

Can you show me what the switch looks like and where it is located? Txs

It's right at the glass lock latch. If you have the hatch cover off, it should be really apparent with two wires. It's just a micro switch.

 

[DIYguybob]

ok... thanks for the info. Does the system response change if you only pull one or the other (ie. pull one and then replace it... does the system now work?) Trying to isolate which item might be an issue. First guess would be the "relay". Have you tried another relay?

Another potential issue is "poor contact" at the relay box. If you notice the pins on the fuse and relay are pretty straight. Over time, the box receptacle "fingers" lose some of the ability to hold a good contact (ie. they are somewhat "spread" / weakened). People have found that putting a "slight twist" on the pins of fuses and relays helps with contact.... kind of making the pin "virtually wider".

ADDED: what year vehicle are you working... sorry if everyone knows but me...

ADDED: it appear that the fuse that are pulling, resets the LGM while the "relay" is for the rear wiper motor.... if I understand correctly from the drawings, its a breaker... maybe the breaker is no good and is sticking / not resetting.

ADDED: Of course, as others have pointed towards the LGM.... maybe you have some marginal wiring at the LGM resulting it being "confused" or the signal wire that it sends to the motor is marginal.

Txs for your response. I have a 2006 Buick Rainier with 4.2L. I have replaced the relay and it made no difference. Initially pulling the relay would make the wiper work again. Now I have to pull both to make it work. I can try pulling just the fuse, but will need to wait until it fails again.
What color is the LGM wire? Where does it connect to and where are the components located?

 

[TJBaker57]

have been pulling fuse 3 and relay 6

Are you perhaps looking at the relay number upside down? I have checked like 5 or 6 references and they all say device 6 is NOT USED.

Guessing you are looking at device 9? And it is not a relay, it is a circuit breaker.

 

[TJBaker57]

What color is the LGM wire? Where does it connect to and where are the components located?

Trunk / Liftgate — 2006 Buick Rainier AWD L6-4.2L VIN S Service Manual | Operation CHARM

Detailed repair manual for the 2006 Buick Rainier AWD L6-4.2L VIN S.

charm.li

Power Trunk / Liftgate Control Module: Diagrams — 2006 Buick Rainier AWD L6-4.2L VIN S Service Manual | Operation CHARM

Detailed repair manual for the 2006 Buick Rainier AWD L6-4.2L VIN S.

charm.li

Wiper and Washer Systems — 2006 Buick Rainier AWD L6-4.2L VIN S Service Manual | Operation CHARM

Detailed repair manual for the 2006 Buick Rainier AWD L6-4.2L VIN S.

charm.li

 

[TJBaker57]

This may help in understanding how the whole business works...

Rear Wiper/Washer System — 2006 Buick Rainier AWD L6-4.2L VIN S Service Manual | Operation CHARM

Detailed repair manual for the 2006 Buick Rainier AWD L6-4.2L VIN S.

charm.li

 

[DIYguybob]

Are you perhaps looking at the relay number upside down? I have checked like 5 or 6 references and they all say device 6 is NOT USED.

Guessing you are looking at device 9? And it is not a relay, it is a circuit breaker.

Hi, the fuse panel under the rear seat has a fuse at #3 and a relay at #9. My mistake, not 6. Earlier vehicles had a circuit breaker. 2006 and later had a relay.

 

[mrrsm]

...and *IF* the final arbiter of having any Broken - Work Hardened Wiring that passes through the upper Roof Conduit are present... they might work intermittently if the broken wire segments occasionally manage to make contact either inside of the Plastic Insulation... or are randomly touching as the Bad Motor Mounts shake the vehicle enough to bring the segments momentarily together... comme ça...

 

[DIYguybob]

...and *IF* the final arbiter of having any Broken - Work Hardened Wiring that passes through the upper Roof Conduit are present... they might work intermittently if the broken wire segments occasionally manage to make contact either inside of the Plastic Insulation... or are randomly touching as the Bad Motor Mounts shake the vehicle enough to bring the segments momentarily together... comme ça...

View attachment 119090View attachment 119091

...and *IF* the final arbiter of having any Broken - Work Hardened Wiring that passes through the upper Roof Conduit are present... they might work intermittently if the broken wire segments occasionally manage to make contact either inside of the Plastic Insulation... or are randomly touching as the Bad Motor Mounts shake the vehicle enough to bring the segments momentarily together... comme ça...

View attachment 119090View attachment 119091View attachment 119092

Thanks for the wiring info. I did find a wire that was bent 90 degrees and poorly conducting, but there must be another wire or other issue causing my problem since I still have the issue.

 

[mrrsm]

That included Wiring Diagram shows where to perform your Continuity Checks between the Unplugged Harness Connectors at the Lift Gate Module...and where they end up at in the final destinations of the Wiper Motor and at the Class 2 Network connections affecting the Wireless FOB interactions. They can and do break -=INSIDE=- of the Finely Colored Insulation and thus make this Continuity Investigation both difficult...AND ...Definitive... ;>)

More On Topic from TV via "The Roadie"

LGM (or LCM) Schematic

Ok, I'm going to throw this out there and see if anyone might have a schematic for the Liftgate Control Module (LGM or LCM) for a 2002 Envoy. I'm looking for the schematic of the board itself, not just a wiring diagram for the connectors going to it (although that would be nice as well). I'm...

www.trailvoy.com

 

[mrrsm]

Here you go... THESE are MUCH Better...

 

[TJBaker57]

Earlier vehicles had a circuit breaker. 2006 and later had a relay.

Relays and circuit breakers are completely different devices. They cannot replace each other. A relay will have no less than 4 connections. A circuit breaker will have just 2.