Intermittent errors with Blind Spot Monitor

[RedlandRanger]

So you have to keep in mind that the code for the CHMSL may be a locked code and must be cleared for the BCM to allow power out, plus also since you have not mentioned it, the 3rd brake light will only be powered when brakes are applied, if the ground test is jumping around and not the same result as the cargo light test- then something is affecting that ground- either a bad ground or a short (between power and ground) - I would do the same test , you do not need the wire from battery (neg) just black lead to body ground and red lead to ground wire (ohms) scale - you should get close to (0) on the C3049 connector then between that connector and the light connector- determine which side of the connector has lost ground, or the light connector- jumper the black wire to ground and then go to the c3049 connector and ohm the black wire to body ground - I think this section is where the fault lies

I wasn't really testing the brake light - I was just making sure the puddle lamps were on - so if they were, the bed lights should have come on. Since I wasn't sure which wire powered the brake light vs the bed lights I just tried them both.

I think I understand what you are saying - you are thinking there is an issue in the ground somewhere between the C3049 connector and the connector to the CHMSL, right? Just thinking out loud, but couldn't I pin in a ground to the CHMSL connector to a good body ground and in theory it should work? (the bed lights, not the brake light) - or I might need to clear the DTC before they will come on? I can jumper the ground and then clear the DTCs and see what happens.

The only reason I did the ground from the battery was trying to eliminate any possible bad grounds - if I went straight to the battery, my thinking was that it HAS to be a good ground so that eliminates me choosing a poor ground spot.

I will experiment some more but it will most likely be a bit (next week maybe unless I squeeze in some time). I've got things the next few days and then we are headed out of town for a few days.

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[RangerBill]

I will experiment some more but it will most likely be a bit (next week maybe unless I squeeze in some time). I've got things the next few days and then we are headed out of town for a few days.

"I think I understand what you are saying - you are thinking there is an issue in the ground somewhere between the C3049 connector and the connector to the CHMSL, right?" Yes, it's possible.

"Just thinking out loud, but couldn't I pin in a ground to the CHMSL connector to a good body ground and in theory it should work? (the bed lights, not the brake light) - or I might need to clear the DTC before they will come on? I can jumper the ground and then clear the DTCs and see what happens." Yes. try that.

 

[airline tech]

So to confirm - you are disconnecting the connector at the light assembly and have the door opened - puddle lights powered and have also tried the cargo light switch , we need to know (eliminate) the light assembly as internally shorted - with it disconnected do you see power at the connector - or are you checking at the circuit board itself

 

[RedlandRanger]

So to confirm - you are disconnecting the connector at the light assembly and have the door opened - puddle lights powered and have also tried the cargo light switch , we need to know (eliminate) the light assembly as internally shorted - with it disconnected do you see power at the connector - or are you checking at the circuit board itself

That is a good call out. I don't think I've tested for power with it disconnected. When I get to this again, I will make sure it is disconnected and test for power at the connector. More to come.

Thank you again for all the suggestions - I keep thinking I've reached my limit and you keep offering ideas - I hope some smoking gun comes up soon so I can fix the issue myself.

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