What should I check on a used semi truck before I buy it?

Check six things: engine codes, brakes, tires, frame, leaks and paperwork. Most costly surprises show up in one of these.

1. Engine computer codes

A scan of the engine computer (ECM) shows active and past fault codes. Old codes can point to repairs the seller did not mention.

2. Brakes and tires

• Brake linings should not be thin or cracked.
• Steer tires need at least 4/32" of tread. Other tires need at least 2/32".

3. Frame and leaks

Look for cracks, welds and rust on the frame rails. Look under the truck for oil, coolant or fuel leaks.

4. Paperwork

Match the VIN on the title to the VIN on the truck door and frame.