Testing Procedure
To ensure correct diagnosis and repair, testing should be done in the following sequence:
- Record Customer Complaint
Ensure all customer complaints or observations are recorded. Test drive vehicle with customer when necessary for malfunction verification. - DLC3 Inspection
Connect the OBD II scan tool or hand-held tester to Data Link Connector No. 3 (DLC3). See Fig 1. If the display indicates a communication fault in the tool, inspect the DLC3. See DATA LINK CONNECTOR NO. 3 INSPECTION under SCAN TOOL PROBLEMS. - Retrieve DTCs & Freeze Frame Data
Retrieve Diagnostic Trouble Codes (DTCs) and record any freeze frame data (if applicable). See RETRIEVING DIAGNOSTIC TROUBLE CODES and FREEZE FRAME DATA . - Clear DTCs & Freeze Frame Data
Clear DTCs and freeze frame data. See CLEARING DIAGNOSTIC TROUBLE CODES . - Visual Inspection
Inspect all electrical connectors and wiring for suspected circuit or component. Ensure all electrical connections are clean and tight. - Check Mode Diagnosis
Set the check mode diagnosis. See CHECK MODE CODE RETRIEVAL under RETRIEVING DIAGNOSTIC TROUBLE CODES. - Confirm Symptoms
Perform road test. Determine if original symptoms are still present. If the engine does not start, perform steps 9 and 10 . - DTC Check
Check the DTC. See SYSTEM OVERVIEW . If there is no malfunction code, go to next step. If there is a malfunction code, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS , then step 11. - Basic Inspection
Perform basic inspection. See BASIC INSPECTION . If the results are OK, go to next step. If the results are not good, inspect the parts and then proceed to step 14. - Determine Symptom
Determine problem symptoms. See SYMPTOM DIAGNOSIS under SYMPTOMS in TROUBLE SHOOTING - NO CODES article. If the problem is in the circuit, go to next step. If the problem is in the parts, inspect the parts and go to step 14. - Check ECM Power Source Circuit
Check the ECM power source circuit. See SYSTEM & COMPONENT TESTING - V6 & V8 article. - Circuit Inspection
Perform the appropriate circuit test. See DIAGNOSTIC TESTS . If the circuit is OK, go to step 14. If the circuit is not good, go to next step. - Intermittent Problem Check
Check for intermittent problems. See INTERMITTENT PROBLEM CHECK . - Verification Procedure
After repairs have been completed, clear all DTCs from ECM. See CLEARING DIAGNOSTIC TROUBLE CODES . Perform road test. Ensure no DTCs exist and all symptoms and/or complaints have been repaired.