Diagnostic System Check - Engine Controls: Description

The Diagnostic System Check is an organized approach to identifying a condition created by an electronic engine control system malfunction. The Diagnostic System Check must be the starting point for any driveability concern. The Diagnostic System Check directs the service technician to the next logical step in diagnosing the concern. Understanding the table and using the table correctly reduces diagnostic time and prevents the replacement of good parts.

Diagnostic System Check - Engine Controls

Step	Action	Yes	No
1	Perform the following preliminary inspections: Ensure that the battery is fully charged. Refer to Battery Inspection/Test (Non-HP2) in Engine Electrical. Ensure that the battery cables are clean and tight. Inspect the easily accessible systems or the visible system components for obvious damage or conditions that could cause the symptom. Refer to Strategy Based Diagnosis in General Information Ensure that the engine and control module grounds are clean, tight, and in the correct location. Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories in Wiring Systems. Did you find and correct the condition?	System OK	Go to Step 2
2	Install a scan tool. Turn ON the scan tool. Does the scan tool turn ON?	Go to Step 3	Go to Scan Tool Does Not Power Up in Data Link Communications
3	Turn ON the ignition, with the engine OFF. Attempt to establish communication with the listed control modules. If you are using a Tech 2, obtain the information using the Class 2 Message Monitor feature: Powertrain control module (PCM) Electronic brake control module (EBCM) Body control module (BCM) Does the scan tool communicate with all the listed modules?	Go to Step 4	Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications
4	IMPORTANT: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter. Refer to the Body Control System Description and Operation in Body Control Systems, for a list of the power mode states that correspond to each ignition switch position. Does the ignition switch parameter reading match the ignition switch position for all switch positions?	Go to Step 5	Go to Power Mode Mismatch in Body Control System
5	Attempt to start the engine. Does the engine crank?	Go to Step 6	Go to Symptoms - Engine Electrical in Engine Electrical
6	Did the engine start and idle?	Go to Step 7	Go to Engine Cranks but Does Not Run
7	IMPORTANT: Do NOT clear the DTCs unless instructed by a diagnostic procedure. Select the DTC display function for the following control modules and record the DTCs: PCM EBCM BCM If multiple powertrain DTCs are stored, diagnose the DTCs in the following order: Component level DTCs. For example, sensor DTCs, solenoid DTCs, and relay DTCs. Begin with the lowest number DTC unless the diagnostic table directs you otherwise. System level DTCs. For example, misfire DTCs, EVAP system DTCs, fuel trim DTCs, and system voltage DTCs. Search for applicable service bulletins. Does the scan tool display any DTCs?	Go to Step 8	Go to Step 9
8	If there are any powertrain DTCs, select Capture Info to store the powertrain DTC information with a scan tool. Did you complete the action?	Go to Diagnostic Trouble Code (DTC) List for applicable diagnostic procedure	-
9	Is the customer's concern with Inspection/Maintenance (I/M) testing?	Go to Inspection/Maintenance (I/M) System Check	Go to Step 10
10	Are there any driveability symptoms observed?	Go to Symptoms - Engine Controls	System OK