Six Step Diagnostic Process

The Six Step Diagnostic Process used by FCA US LLC is a time proven process. The basic concepts of this process have been used by others for problem solving for many years. The successful application of this process requires a solid understanding of the conditions that affect each step, and when its time to advance to the next step. These conditions based on experience formulate what is known as "Best Practices".

Accurate and consistent vehicle repairs do not happen by accident. They are the result of sound diagnostic practices and principals. These principals are rooted in the Six Step Diagnostic Process and require the application of logical reasoning by the technician.

The Six-Step Diagnostic Process is a logical procedure through which problems in any of the vehicle electrical sub-systems can be diagnosed. Do not skip any steps, or jump ahead.

The Six-Step Diagnostic Process must be performed in the following sequence:

VERIFY THE CUSTOMER COMPLAINT
DETERMINE RELATED SYMPTOMS
ANALYZE THE SYMPTOMS
ISOLATE THE TROUBLE
REPAIR THE TROUBLE
VERIFY PROPER OPERATION

STEP 1 : VERIFY THE CUSTOMER COMPLAINT
Before any diagnostic process can progress beyond the first step, it is essential to verify the customer's complaint. Because it is critical to verify the problem, it may be necessary to operate the vehicle under the same conditions as the customer does when the problem occurs. This requires an accurate description of the problem condition from the customer and may include a test drive with the customer. When verification cannot be confirmed it is possible that a problem does not exist. After verification and throughout the diagnostic process, always keep in mind the original customer complaint.

STEP 1 : VERIFY THE CUSTOMER COMPLAINT

Before any diagnostic process can progress beyond the first step, it is essential to verify the customer's complaint. Because it is critical to verify the problem, it may be necessary to operate the vehicle under the same conditions as the customer does when the problem occurs. This requires an accurate description of the problem condition from the customer and may include a test drive with the customer. When verification cannot be confirmed it is possible that a problem does not exist. After verification and throughout the diagnostic process, always keep in mind the original customer complaint.

STEP 2 DETERMINE RELATED SYMPTOMS
This step is a continuation of the first step as information is still being gathered and no changes or repairs have been performed. Sometimes the actual fault conditions, causing a customer concern, affect other systems as well. When you are sure that a problem does exist, perform operational checks on all components connected to the problem circuit. For example, if the complaint was that the Center High Mounted Stop Lamp (CHMSL) was inoperative, check the other stop lamps and turn signals for proper operation. Check associated circuits that use the same circuit protection device. Refer to the Service Information and wiring diagrams to determine how they may be related. Be aware of problems that affect a single function of a system, an entire system or multiple systems. If multiple problems are identified, attempt to determine how they may be related. When systems share common circuits, a single repair can often correct multiple conditions.

STEP 2 DETERMINE RELATED SYMPTOMS

This step is a continuation of the first step as information is still being gathered and no changes or repairs have been performed. Sometimes the actual fault conditions, causing a customer concern, affect other systems as well. When you are sure that a problem does exist, perform operational checks on all components connected to the problem circuit. For example, if the complaint was that the Center High Mounted Stop Lamp (CHMSL) was inoperative, check the other stop lamps and turn signals for proper operation. Check associated circuits that use the same circuit protection device. Refer to the Service Information and wiring diagrams to determine how they may be related. Be aware of problems that affect a single function of a system, an entire system or multiple systems. If multiple problems are identified, attempt to determine how they may be related. When systems share common circuits, a single repair can often correct multiple conditions.

STEP 3 ANALYZE THE SYMPTOMS
This step is depends on verifying the problem and builds on the information gathered from Steps 1 and 2. Using Service Information, determine what components are required for the affected system to operate. Whenever possible verify the operation of each of these components. Each item that functions properly can likely be ruled out as a possible cause of faulty operation. The more complete the assessment of the vehicle is at this step the less time wasted later on. Know what you must verify about the vehicle systems based on your assessment before you begin. If a circuit is inoperative identify the wire colors and connectors that support that circuit. If possible identify any component test procedures in the Service Information that may help identify suspected components.

STEP 3 ANALYZE THE SYMPTOMS

This step is depends on verifying the problem and builds on the information gathered from Steps 1 and 2. Using Service Information, determine what components are required for the affected system to operate. Whenever possible verify the operation of each of these components. Each item that functions properly can likely be ruled out as a possible cause of faulty operation. The more complete the assessment of the vehicle is at this step the less time wasted later on. Know what you must verify about the vehicle systems based on your assessment before you begin. If a circuit is inoperative identify the wire colors and connectors that support that circuit. If possible identify any component test procedures in the Service Information that may help identify suspected components.

STEP 4 ISOLATE THE TROUBLE
Depending on the problem this step has many variables. It can range from the isolation of a single component to the disassembly of a portion of the vehicle. If proper planning was used during Step 3 this step should provide positive results. Sometimes the problem is traced to a faulty component or a portion of the wiring. Often the isolation of the problem involves using the split half technique. If the symptom goes away after disconnecting a component or portion of the wiring, it means you have identified the problem area. During the "Isolating the Trouble" phase of the diagnostic process you must be constantly aware of any changing vehicle conditions. Always keep in mind the original customer complaint. Be aware of trouble conditions that suddenly escalate when components are changed or replaced. When a problem gets larger as a result of the repair actions, attempt to back up and reverse the negative condition. The cause of the problem (after it is located) is usually very simple and very logical and the symptoms support the fault condition. Common sense indicates that properly interpreted symptoms usually point to the problem. Unless the complexity of a problem has been made worse during the repair process, most of the vehicle problems are caused by a single fault. Swapping or replacing multiple components such as electronic modules almost always escalates the problem. It makes sense to avoid this practice. Any diagnostic process that uses DTCs as the only reason to replace parts is faulty at best. At the least, the Diagnostic Tool (and any other necessary diagnostic equipment) should be used associate or clear vehicle components.

STEP 4 ISOLATE THE TROUBLE

Depending on the problem this step has many variables. It can range from the isolation of a single component to the disassembly of a portion of the vehicle. If proper planning was used during Step 3 this step should provide positive results. Sometimes the problem is traced to a faulty component or a portion of the wiring. Often the isolation of the problem involves using the split half technique. If the symptom goes away after disconnecting a component or portion of the wiring, it means you have identified the problem area. During the "Isolating the Trouble" phase of the diagnostic process you must be constantly aware of any changing vehicle conditions.

Always keep in mind the original customer complaint.
Be aware of trouble conditions that suddenly escalate when components are changed or replaced.
When a problem gets larger as a result of the repair actions, attempt to back up and reverse the negative condition.
The cause of the problem (after it is located) is usually very simple and very logical and the symptoms support the fault condition. Common sense indicates that properly interpreted symptoms usually point to the problem.
Unless the complexity of a problem has been made worse during the repair process, most of the vehicle problems are caused by a single fault.
Swapping or replacing multiple components such as electronic modules almost always escalates the problem. It makes sense to avoid this practice.
Any diagnostic process that uses DTCs as the only reason to replace parts is faulty at best. At the least, the Diagnostic Tool (and any other necessary diagnostic equipment) should be used associate or clear vehicle components.

STEP 5 REPAIR THE TROUBLE
After the problem has been isolated, make the necessary repairs. Be sure to follow the repair procedures in the Service Information using the recommended techniques, parts and materials to ensure that the problem has been corrected. Any repairs to wiring or connectors should take into consideration the cause of the fault condition. If the problem was caused by incorrect routing of the wiring the repair should include the relocating of the harness in the correct location to prevent a repeat occurrence. If the condition was caused by water intrusion find the source of the leak and repair the problem.

STEP 5 REPAIR THE TROUBLE

After the problem has been isolated, make the necessary repairs. Be sure to follow the repair procedures in the Service Information using the recommended techniques, parts and materials to ensure that the problem has been corrected. Any repairs to wiring or connectors should take into consideration the cause of the fault condition. If the problem was caused by incorrect routing of the wiring the repair should include the relocating of the harness in the correct location to prevent a repeat occurrence. If the condition was caused by water intrusion find the source of the leak and repair the problem.

STEP 6 VERIFY PROPER OPERATION
Take the time to perform a quality control check before you return the vehicle to the customer to reduce comebacks and improve customer satisfaction. Before returning the vehicle to the customer, verify that not only the original complaint has been corrected, but also vehicle systems which were not part of the repair were tested to determine if the repair procedure caused any other undesirable conditions. Depending on the conditions repaired this may require that you operate the vehicle in the same conditions as in Steps 1 and 2. If the original complaint has been corrected the vehicle can now be returned to the customer.

STEP 6 VERIFY PROPER OPERATION

Take the time to perform a quality control check before you return the vehicle to the customer to reduce comebacks and improve customer satisfaction. Before returning the vehicle to the customer, verify that not only the original complaint has been corrected, but also vehicle systems which were not part of the repair were tested to determine if the repair procedure caused any other undesirable conditions. Depending on the conditions repaired this may require that you operate the vehicle in the same conditions as in Steps 1 and 2. If the original complaint has been corrected the vehicle can now be returned to the customer.