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(888) 312-8812 Login SignupThe Mack DEF Level Sensor monitors diesel exhaust fluid level in the DEF tank, not the brake fluid reservoir. This correction matters because the part belongs to the emissions fluid system rather than the hydraulic brake system. Its sensor function helps the vehicle read DEF level information through the appropriate tank-mounted assembly. The Mack 23539923 is a 21-inch DEF level sensor for service work focused on diesel exhaust fluid monitoring.
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