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Since the motor has been replaced and the BCM checked out fine. That means they would of also verified the multifunction switch signal to the BCM is good. Why they stopped there with there diag makes no sense, so it makes me wonder if there diag steps were even accurate. If it was then the wiper speed control relay is the next part that could be to blame.
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That indicates the BCM check out, possibly was not confirmed there was no issue with the BCM. Do you have a diagnostic tool and understand wire diagrams and electrical testing?
Great look over the wire diagram below.
At the multifunction switch, see the wipers to high and OHM test across the tan/black and light green. You should get no resistance. Let me know those results.
I have never had an air bag accidentally go off being I often have to do electrical testing in the steering column, though if your worried disconnect the battery prior to working and yes the steering column shrouds need to be removed.
The meters audible tone just responds with the presence of continuity it does not tell you if there is resistance, so it is not accurate for this test.
The key is off, the connector can be back probed or the connector removed and those pins tested on the switch.
Multi function switch is good with those results. Remove the wiper speed control relay. Pin 86 must be a ground when commanding the wipers on high with the key on, if its not then the BCM is bad.
Sorry I can not show you diagrams over the phone.
Use the link below, you remove the relay and OHM test this pin to ground to see if there is no resistance.
There should be a pin chart on the bottom or side of the relay.
That reading indicates teh BCM is not sending a ground to the relay meaning the BCM is to blame.
According to the diagram the dark green wire to the wiper motor is powered to achieve high speed.
The BCM is under the left side of the dash and requires a dealer equivalent diagnostic tool to program it.
Based on your tests results if done correct then I am 90% confident its the BCM. I can never gaurantee it, being I am not there. I am using your eyes and hands.
Its apparent the assistance I am providing is not of benefit, being this has gone on almost a month now. I feel its best to opt out and let someone else try to help you.
new expert here did you still need help ?