Rear Hatch release not working
Thread Starter
Cruising
Joined: May 2012
Posts: 10
Likes: 0
Rear Hatch release not working
Not sure where to look next, any help much appreciated..
99 hardtop, rear hatch not releasing with key fob or dash switch.
Checked relay and fuse 26, both good.
If I jump terminals 30 and 87 Simulating power to the relay coil the rear hatch solenoid activates and hatch opens so I'm assuming that side of the circuit is not the problem.
When the hatch is manually popped the "hatch open" warning on the DIC illuminates so that circuit is good.
Next I pulled the hatch release switch from the dash (no fog light option on car). The orange wire is hot with 12.4 volts and the black reads resistance of 2.7ohms (meter set to 20k scale) to ground not sure of that's the correct reading or not.
Also checked and cleaned the grounds on both sides behind the headlights on the frame rails based on other posts I've read on the forum.
Any suggestions on how to proceed?
I'm hoping its not a BCM issue. All other electrical circuits in car work.
Thanks
99 hardtop, rear hatch not releasing with key fob or dash switch.
Checked relay and fuse 26, both good.
If I jump terminals 30 and 87 Simulating power to the relay coil the rear hatch solenoid activates and hatch opens so I'm assuming that side of the circuit is not the problem.
When the hatch is manually popped the "hatch open" warning on the DIC illuminates so that circuit is good.
Next I pulled the hatch release switch from the dash (no fog light option on car). The orange wire is hot with 12.4 volts and the black reads resistance of 2.7ohms (meter set to 20k scale) to ground not sure of that's the correct reading or not.
Also checked and cleaned the grounds on both sides behind the headlights on the frame rails based on other posts I've read on the forum.
Any suggestions on how to proceed?
I'm hoping its not a BCM issue. All other electrical circuits in car work.
Thanks
Thread Starter
Cruising
Joined: May 2012
Posts: 10
Likes: 0
Thanks
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
The FOB interacts with the BCM via the serial bus for the trunk. The trunk switch has the ground side go to the BCM which then interacts internally to ground a separate circuit to activate/ground the relay 39 coil.
The serial bus input activates the same internal BCM circuit to activate/ground relay 39.
I think the BCM is the issue, or you have an issue in the wiring from the BCM to relay 39. This assumes you ARE getting voltage to relay 39.
The BCM interacts with relay 39 from Pin B9 in BCM connector C1, it is a Light Blue wire. This connector is the center one at the BCM. Here is the pin out.
I can scan the schematic later for you if you want it. If you want to avoid replacing the BCM or trying to fix it now, you could just temporarily take relay 39 to a switch to activate the trunk.
Please let me know if you need anything else. Mr. Sam
Also try disconnecting the battery for a few minutes to reboot the BCM. It's free. Also, if you don't know how to remove the pins from the connectors for testing circuits let me know.
The serial bus input activates the same internal BCM circuit to activate/ground relay 39.
I think the BCM is the issue, or you have an issue in the wiring from the BCM to relay 39. This assumes you ARE getting voltage to relay 39.
The BCM interacts with relay 39 from Pin B9 in BCM connector C1, it is a Light Blue wire. This connector is the center one at the BCM. Here is the pin out.
I can scan the schematic later for you if you want it. If you want to avoid replacing the BCM or trying to fix it now, you could just temporarily take relay 39 to a switch to activate the trunk.
Please let me know if you need anything else. Mr. Sam
Also try disconnecting the battery for a few minutes to reboot the BCM. It's free. Also, if you don't know how to remove the pins from the connectors for testing circuits let me know.
Last edited by dadaroo; May 5, 2014 at 09:49 AM.
Thread Starter
Cruising
Joined: May 2012
Posts: 10
Likes: 0
The FOB interacts with the BCM via the serial bus for the trunk. The trunk switch has the ground side go to the BCM which then interacts internally to ground a separate circuit to activate/ground the relay 39 coil.
The serial bus input activates the same internal BCM circuit to activate/ground relay 39.
I think the BCM is the issue, or you have an issue in the wiring from the BCM to relay 39. This assumes you ARE getting voltage to relay 39.
The BCM interacts with relay 39 from Pin B9 in BCM connector C1, it is a Light Blue wire. This connector is the center one at the BCM. Here is the pin out.
I can scan the schematic later for you if you want it. If you want to avoid replacing the BCM or trying to fix it now, you could just temporarily take relay 39 to a switch to activate the trunk.
Please let me know if you need anything else. Mr. Sam
Also try disconnecting the battery for a few minutes to reboot the BCM. It's free. Also, if you don't know how to remove the pins from the connectors for testing circuits let me know.
The serial bus input activates the same internal BCM circuit to activate/ground relay 39.
I think the BCM is the issue, or you have an issue in the wiring from the BCM to relay 39. This assumes you ARE getting voltage to relay 39.
The BCM interacts with relay 39 from Pin B9 in BCM connector C1, it is a Light Blue wire. This connector is the center one at the BCM. Here is the pin out.
I can scan the schematic later for you if you want it. If you want to avoid replacing the BCM or trying to fix it now, you could just temporarily take relay 39 to a switch to activate the trunk.
Please let me know if you need anything else. Mr. Sam
Also try disconnecting the battery for a few minutes to reboot the BCM. It's free. Also, if you don't know how to remove the pins from the connectors for testing circuits let me know.
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
If you want to discuss just PM me with your phone number. Talking instead of "texting" is typically better on issues like this.
Just thought about this: If you have another FOB see if you can get it to release the trunk. More info is better. I'll bet it does not work either, but it could.
Just thought about this: If you have another FOB see if you can get it to release the trunk. More info is better. I'll bet it does not work either, but it could.
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
Thread Starter
Cruising
Joined: May 2012
Posts: 10
Likes: 0
If you want to discuss just PM me with your phone number. Talking instead of "texting" is typically better on issues like this.
Just thought about this: If you have another FOB see if you can get it to release the trunk. More info is better. I'll bet it does not work either, but it could.
Just thought about this: If you have another FOB see if you can get it to release the trunk. More info is better. I'll bet it does not work either, but it could.
So I guess bad news is BCM?
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Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
To use the hatch/trunk lid release on vehicles with an
automatic transmission, your vehicle must be in
PARK (P) or NEUTRAL (N). For manual transmissions,
set the parking brake. See “Parking Brake” in the Index.
You can't find this info in the FSM and there is no direct input to the BCM.
I have a manual and I am curious if I can actually pop the trunk without setting the parking brake. Wish my car was at home.
Le Mans Master
Joined: Oct 2003
Posts: 6,126
Likes: 19
From: Streamwood illinois
My vert will not pop trunk unless ebrake is on on the 6 spd . If contact is bad at ebrake switch in tunnel area trunk will not open. Does ebrake light illuminates when ignition on and brake on? If not, that's your issue.
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 302
From: Columbia SC
Thread Starter
Cruising
Joined: May 2012
Posts: 10
Likes: 0
At this point I'm inclined to go with the inexpensive fix you suggested.
If I re-route the light blue wire on connector c-1 directly to the dash trunk release switch will that work? I understand I will bypass the BCM completely and key fobs will not open trunk should I go this route and trunk will open anytime that switch is pushed, parked or moving.
I do not have the fog light option and the dash trunk switch has six wires; orange, orange/brown, yellow, black, brown and white.
Haven't checked yet but I assume the black is to ground so just need to figure out which of the other wires to splice into.
Does that sound like a workable solution?
Thanks again for all the great insight and advice.