Chevrolet Colorado & GMC Canyon Forum banner
1 - 8 of 8 Posts

·
Premium Member
Joined
·
3,590 Posts
The control side of the relay is terminals 85 and 86. The relay operation is controlled by the BCM, which provides a ground for the control circuit at terminal 86. Terminal 85 is powered from the battery bus and is hot at all times. With the relay removed find the terminal sockets. When standing at the left front fender, terminals 30 and 85 will be on the right, towards the firewall with 86 and 87 on the left. Compare it with the relay.

With power off, light switch off, there should be 12 volts at terminal 85 and also at 30. With a meter, probe terminal 85 with the red lead and terminal 86 with the black. There should be no voltage present. If using a test light, it should not illuminate. If there is a voltage reading, it indicates that the BCM is keeping the relay turned on.

Let us know what you find.
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #7 ·
The control side of the relay is terminals 85 and 86. The relay operation is controlled by the BCM, which provides a ground for the control circuit at terminal 86. Terminal 85 is powered from the battery bus and is hot at all times. With the relay removed find the terminal sockets. When standing at the left front fender, terminals 30 and 85 will be on the right, towards the firewall with 86 and 87 on the left. Compare it with the relay.

With power off, light switch off, there should be 12 volts at terminal 85 and also at 30. With a meter, probe terminal 85 with the red lead and terminal 86 with the black. There should be no voltage present. If using a test light, it should not illuminate. If there is a voltage reading, it indicates that the BCM is keeping the relay turned on.

Let us know what you find.
There is voltage showing. Not sure what to do next.
 

·
Premium Member
Joined
·
3,590 Posts
The BCM provides the ground for the control side of the relay. Either that is happening all the time, or the wiring from the fuse box to the BCM has been chaffed through and grounded someplace. Try disconnecting the Black connector at the BCM and see if you still have voltage, in the fuse box, between the receptacles for 85 and 86. The Brown wire with White stripe in the Black connector is the relay circuit.
 
1 - 8 of 8 Posts
Top