Common scenarios which often require more than one hour of diagnostic time:
- Intermittent problems: can be difficult to duplicate. See the PHAD policy on intermittent problems.
- Parasitic battery draws, shorted/open wires in harness: can be time-consuming to track down, especially if interior or exterior panels have to be removed for proper access.
- Aftermarket accessories: alarm systems, remote start, snow plow/brake controllers, lighting, tuners etc. may be interfering with stock vehicle operation.
- Improper previous repairs: faulty aftermarket components, improper harness routing, splicing, etc. may have to be repaired before the actual diagnosis can begin. Sometimes correcting improper repairs solves the initial problem!
- European vehicles: are generally more complex and require more disassembly to access components and wiring. Euro OEM information and wiring diagrams are at times difficult to obtain and use.
- Rare or classic vehicles: as with European makes, proper information (diagnostic procedures, wiring diagrams, etc.) is often difficult to obtain for classic or rare models.