If you are getting a message that says "Service 4 wheel drive" and the switch light blinks after attempting to make a shift then odds are about 60% that you have a faulty encoder sensor that's part of the shift motor on the transfer case or the push button switch on the dash is faulty. If you can get someone with a scan tool to read the service codes then the code will direct you to which one it is. You could also have some other problem but those two items are what I see fail most often.
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If you are getting a message that says "Service 4 wheel drive" and the switch light blinks after attempting to make a shift then odds are about 60% that you have a faulty encoder sensor that's part of the shift motor on the transfer case or the push button switch on the dash is faulty. If you can get someone with a scan tool to read the service codes then the code will direct you to which one it is. You could also have some other problem but those two items are what I see fail most often.