Door locks and window operation

Tiny
BUTCHRENO
  • MEMBER
  • 2004 JEEP GRAND CHEROKEE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 90,000 MILES
The driver door lock works from driver module the left driver window works and left passenger window works. But no right side windows or door locks or lift gate locks will work from master switch?
I have checked all door wiring and fuses.
Thursday, July 30th, 2020 AT 9:47 AM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

If the switches are all good and have power, the next concern is a breakdown in communication between the modules. The PCI bus signals the passenger side and opposite.

Basically, the modules are tied together via the a can bus system. CAN stands for computer area network. With it, the manufacturer can tie multiple modules together to communicate with very little wiring. They started using this as there was an increase of computer and modules in the vehicle. It was to eliminate weight from the massive amounts of wiring that was needed.

If you look at the attached pic, I highlighted the bus system between the modules. The way this needs tested is by scanning the CAN bus system. That checks all communications between all modules to see if there is a break down. It should indicate if there is an issue with this situation.

Here is a video that shows how it's done and what can be found doing it:

https://youtu.be/InIlnsjOVFA

Let me know what you find or if you have other questions.

I just spoke with the owner of the site about this. He indicated that 9 out of 10 times, the module itself is bad. He suggested replacing that first.

Take care,
Joe

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Thursday, July 30th, 2020 AT 1:33 PM
Tiny
BUTCHRENO
  • MEMBER
  • 6 POSTS
Found a module and installed but exactly the same results. Passenger side door locks and windows will not work. Any new suggestions?
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Sunday, September 27th, 2020 AT 8:08 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Were you able to scan the can bus system? At this point, I have a feeling that is where the problem is coming from.

Let me know.
Joe
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Sunday, September 27th, 2020 AT 6:20 PM
Tiny
BUTCHRENO
  • MEMBER
  • 6 POSTS
No, cannot locate anyone who has a scanner other than a dealer. They want a ton just to check. I rechecked power and ground for both doors they are good. I don't know if there is a way to check the remaining wiring?
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Tuesday, September 29th, 2020 AT 8:52 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
What makes this difficult is the can system. That really is where the sanner needs to come in to play. If you have power and ground, either a switch is bad or there is a break down in the can system. Have you checked each of the switch to see if there is both power in and out of that switch?

Joe
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Tuesday, September 29th, 2020 AT 7:09 PM
Tiny
BUTCHRENO
  • MEMBER
  • 6 POSTS
No, I haven't. Do I do this at the plug at the control module? Or do I need to go into the back of the plug with it connected to the control module?
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Friday, October 2nd, 2020 AT 4:52 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
When you check for power at the switch, you do it right where the plug is located. You can back probe the wires to see if there is power in. Once the switch is actuated, you can check for power out.

Joe
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Sunday, October 4th, 2020 AT 4:50 PM

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