Pre-Delivery Inspection (PDI)
- Verify that the trailer's physical components match the documented VIN and GVWR specifications.
- Perform a comprehensive mechanical and electrical systems check covering torque, pressure, and function.
- Document and sign off on all PDI readings to ensure accountability and customer satisfaction.
- Torque wrench — Check the torque on every lug nut to ensure wheel security.
- Tire pressure gauge — Measure cold tire pressure for comparison against the sidewall or placard.
- PDI sheet — Record all inspection readings and technician signatures for official documentation.
Check torque on every lug nut, tire pressure (cold) against the applicable trailer tire-information placard and manufacturer instructions, and lights, brakes and breakaway function.
Verify the VIN tag, GVWR and tire sizes match the paperwork.
Operate every door, ramp, jack and hydraulic function through full travel.
Record readings on the PDI sheet and have the technician sign it.
How It Works
Verification of Identity and Capacity
Before mechanical testing begins, the technician must verify that the VIN tag, GVWR, and tire sizes match the trailer's paperwork. This ensures the customer receives the correct unit as ordered and that the trailer is legally and technically compliant.
Comprehensive Functional Testing
A PDI requires the operation of every moving part through its full travel. This includes doors, ramps, jacks, and hydraulic functions. Testing full travel identifies obstructions or mechanical failures that might not be apparent in a partial movement test.
Safety System Validation
Critical safety systems including lights, brakes, and the breakaway function must be tested. Additionally, wheel security is confirmed by checking torque on every lug nut, and tire safety is ensured by matching cold pressure to placard or sidewall specs.
Diagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Wheel lug nuts do not meet required tightness. | Check torque on every lug nut using a calibrated torque wrench. | Per the applicable manual | Factory oversight or loosening during transport. Basis: General shop practice (not from a downloaded manual) |
| Tire pressure is incorrect for the load rating. | Measure cold tire pressure and compare to the unit markings. | Match the sidewall or placard. | Environmental temperature changes or improper inflation during assembly. Basis: General shop practice (not from a downloaded manual) |
| Discrepancy between trailer and registration documents. | Verify the VIN tag, GVWR, and tire sizes against the paperwork. | Must match the paperwork. | Administrative error or incorrect unit selection. Basis: General shop practice (not from a downloaded manual) |
| Hydraulic or mechanical components bind during operation. | Operate every door, ramp, jack and hydraulic function through full travel. | Full travel without obstruction. | Mechanical interference, lack of lubrication, or component failure. Basis: General shop practice (not from a downloaded manual) |
At the Bay: Diagnose the Case
CASE 1 / 4
Wheel lug nuts do not meet required tightness.
- Test
- Compare
- Correct
Select the next check
Basis: General shop practice (not from a downloaded manual). A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Ignoring the VIN tag and GVWR verification against paperwork.
- ✕ Testing tire pressure when tires are hot from road use.
- ✕ Only testing doors or ramps through partial movement instead of full travel.
- ✕ Failing to record specific readings on the PDI sheet.
- ✕ Checking only a sample of lug nuts instead of every nut.
- ✕ Skipping the breakaway function test during the brake check.
Quick Check
Practice only — not scored.
Source: General shop practice (not from a downloaded manual)