Seven Step Diagnostic Process
The Seven Step Diagnostic Process is a structured approach to diagnosing and repairing equipment problems. Following this process ensures thorough diagnosis, prevents unnecessary part replacement, and results in complete, documented repairs.
Step 1: Verify Operator Concern
Perform operational and functional tests to verify the customer's concern.
- Don't assume the condition of a component or system - check it out!
- Record the failure in a snapshot file
- If unable to duplicate the failure, ask the operator or consult your team leader
Questions to Ask
- When does the problem occur? How often?
- Under what conditions? Speeds, loads, functions, temperatures?
- How long ago did the symptoms start?
- Did the problem begin gradually or suddenly?
- Is the problem intermittent?
- What happened, and in what order?
- Is the equipment being used in the right application?
- Does the customer perceive a problem that is really normal operation?
Summarize your factual findings and write a detailed "Concern" section in your service report. Include information on how you duplicated the concern.
Important: Any diagnosis made without verifying the customer's concern is nothing more than SWAG - "Scientific Wild-Ass Guess."
Step 2: Inspect the Machine
Complete a thorough inspection of the machine. Use this inspection as an opportunity to start your diagnosis.
During Inspection
- Take mental note of systems on the machine that DO work
- Try out the machine options and all control patterns
- Can you focus the failure to machine systems like hydraulic versus electrical?
- Could the problem be software settings?
- Can you isolate a hydraulic problem between pressure/flow or pilot system?
Document Everything
- Note active codes and warning icons from displays
- Note active and logged codes and events from the Service Log
- Save Service Log
- Save screen capture of ECU and DCU codes
- Save ECU or DCU Snapshot of active failure
- Save all code information, then clear codes, test operate, and see what reoccurs
Don't Forget the Basics! Take note of what DOES work on the machine. This information may help isolate parts of the machine systems.
Step 3: List Possible Causes
Use factual findings from Steps 1 and 2 to generate a list of possible causes.
- Use schematics and service information to identify all possible components that may cause the problem
- List from most likely and easiest to test, to most unlikely and difficult
- Is the cause likely warranty? Research Warranty Requirement Articles now
Use All Your Resources
- Service Manuals and Schematics
- TSBs (SNFT, Quality Alerts, Service Letters, Knowledge Articles)
- Troubleshooting Guides
- RTC: Service Support Insights and Community
- Cases
- Technical Information Bulletins
- Install Instructions
- Training Resources
Step 4: Determine Root Cause
Make a plan. What are the least expensive, easiest to test components you can eliminate first?
- Perform diagnostic tests and adjustment procedures to eliminate items from your cause list
- Splitting the system may help narrow down the cause
System Splitting Strategies
- Low pressure or High pressure (Pilot or Work Circuit)
- Electrical, Hydraulic, or Mechanical
- Machine Control (computer), Software, or Battery Circuit
- Relay (control or power circuit)
Multiple Symptoms
If more than one symptom exists, look for common causes. Or choose the easiest to diagnose and diagnose it to its root cause. When you find the root cause of this failure, you might also solve others.
Before You Order Parts: Ask yourself - if this part doesn't fix the problem, what will I do next? Then do that thing BEFORE you order the part.
When you find a cause for a system not working, bypass it if possible. Make sure the rest of the system works before quoting the customer. Find ALL the failures related to the customer's concern.
Step 5: Repair
Use current service information to complete the repair.
- Are there updated parts or procedures?
- Consult Diagnostic Guides
- Check Technical Service Bulletins
- Review Service Support Site
- Check Parts Bulletins
Step 6: Verify the Repair
- Recreate the circumstances used to duplicate the customer's concern
- Verify that the customer concern has been resolved
- Does the repair ensure that the symptoms do not re-occur?
- If in-service factors remain which may cause a reoccurrence, discuss with the Service Manager
Step 7: Write the Report
Write a detailed service report that includes the three "C"s:
- Customer Concern - What the customer reported and how you verified it
- Cause - The root cause you identified
- Correction - Tests performed, parts replaced, suggestions to customer, and repairs completed
Document improper maintenance or operation. A good service report will include details from Steps 1 through 6.