If the police officer is willing to say that you gave your consent (when you did not), then the mj won't be suppressed.
If the police officer is willing to say that he smelled mj, when he did not, then the mj will not be suppressed.
If the police officer is willining to say that he saw a baggie or rolling paper peeking out of your centre console, when in reality the baggie was out of sight in your glove box, then the mj will not be suppressed.
Refusing consent is one of the best options that you have (the best is don't drive with mj), but refusing consent doesn't mean that you will have any meaningful remedy if the policeman searches your car after you refuse consent. Your best hope is that the policeman just goes away after you refuse consent, but many will go ahead and search anyway.
The worst are the policemen who plant. Then you can be locked up even if you had no mj at all. Only a small minority of policemen plant, but you can't tell ahead of time which ones do plant mj in vehicles. If they plant there is nothing you can do because it is impossible to argue that a policeman planted evidence (at least without video, and even then it is difficult).