Is it defined as a commercial vehicle under federal code? Then you must submit to inspection. State statutes have similar requirements for state officials.
IANAL, but the Fifth Amendment says that a person cannot be compelled to be “a witness against himself”. I’m sure there are numerous rulings and precedents about what it means to be a “witness” but I believe this is about making statements, not about performing actions. Otherwise, you could refuse to open the door for officers with a valid warrant, on the grounds that it would lead to your incrimination.
IANAL. The law linked by Loach states that a driver has to “stop and submit to inspection”. It seems to me that submitting does not include assisting with the inspection, beyond what’s necessary to allow the officer to perform the inspection himself. So give him the keys to everything, produce the required records, and you’re within the requirements of the law.
But you’ve now annoyed the officer who is going to actually perform the inspection, without in any way limiting his ability to do so. It’s not like the case if an officer asks if you consent to him searching your private vehicle and you say “No”, and he has no further legal power to do so. He’s going to turn those switches on himself anyway, so you’re going to get dinged for the same penalties regardless of whether you assist in the inspection or not.
Plus the inspection will now take longer, and you’re less likely to get away with a warning for any minor infractions.
(What I meant was, being able to say in court “This is wrong, I can’t be required to testify against myself, if no one will testify against me then I should go free” is very obviously useful to the accused, and it changes a potentially unfair situation into one that’s much more fair. But being able to say “This is wrong, I can’t be required to turn my truck lights on, if they are broken the police should find out for themselves” brings no one any advantage, and doesn’t fix any unfair situation at all.)
When stopped by officials in most countries the “attitude test” is vital. A polite, cooperative driver is far more likely to get off a minor offence (“Get that stop lamp fixed ASAP”) than a surly, uncooperative, “I know my rights” driver who will get a ticket for the stoplight as well as the dubious tyre and the too-dark privacy glass.
If you don’t assist the DOT officer with your vehicle inspection, then your vehicle will be stopped. Your vehicle will not be going anywhere. Operating a vehicle isn’t a right.