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For 1990-2009 cars only
Makes 🢒 Generic 🢒 2005 🢒 Unit Repair 🢒 Preface 🢒 Cautions and Notices 🢒 Diagnostic System Check - Vehicle

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step ensures that the battery, and the vehicle primary power and ground systems are functioning correctly.

    2.

  2. Lack of communication may be due to a particular malfunction of a serial data circuit. The link to Data Link References will provide a list of modules and the associated data network no communication diagnostic link.

    3.

  3. A Power Mode Master, which is operating in the incorrect power mode based on key position, may cause other symptoms and/or DTCs to set. The link to Power Mode Mismatch will correct the condition before checking for module DTCs or symptoms.

Step

Action

Yes

No

1

Perform the following preliminary inspections:

    • Ensure that the battery is fully charged. Refer to Battery Inspection/Test in Engine Electrical.
    • Ensure that the battery cables are clean and tight.
    • Inspect for any open fuses. Refer to Power Distribution Schematics and Electrical Center Identification Views .
    • Inspect the easily accessible systems or the visible system components for obvious damage or conditions that could cause the symptom.
    • Ensure that the grounds are clean, tight, and in the correct location. Refer to Ground Distribution Schematics and Power and Grounding Component Views .
    • Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories in Wiring Systems.
    • Search for applicable service bulletins.

Did you find and correct the condition?

System OK

Go to Step 2

2

Install a scan tool.

Does the scan tool power up?

Go to Step 3

Go to Scan Tool Does Not Power Up in Computer/Integrating Systems

3

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with all of the control modules on the vehicle. Refer to Data Link References in Computer/Integrating Systems for the modules you should expect to observe.

Does the scan tool communicate with all of the expected vehicle control modules?

Go to Step 4

Go to Data Link References in Computer/Integrating Systems

4

Important: 

   • To ensure that retained accessory power (RAP) mode is inactive, if equipped, open the driver door during the following step.
   • The engine may start during the following step. Turn OFF the engine as soon as you have observed the crank power mode.

  1. Access the Power Mode parameter on the scan tool.
  2. Rotate the ignition switch, operate the ignition mode switch, through all positions while observing the Power Mode parameter. Refer to Body Control System Description and Operation in Computer/Integrating Systems for a list of the power mode states that correspond with each switch position.

Does the Power Mode parameter reading on the scan tool match the ignition switch position for all switch positions?

Go to Step 5

Go to Power Mode Mismatch in Computer/Integrating Systems

5

Attempt to start the engine.

Does the engine crank?

Go to Step 6

Go to Symptoms - Engine Electrical in Engine Electrical

6

Attempt to start the engine.

Does the engine start and idle?

Go to Step 7

Go to Engine Cranks But Does Not Run in Engine Controls - 3.5L (LX9)

7

Important: Do NOT clear any DTCs unless instructed by a diagnostic procedure.

  1. Diagnose the DTCs in the order that the DTCs appear on the scan tool or mis-diagnosis may occur.
  2. If multiple powertrain DTCs are stored, diagnose the DTCs in the following order:
    3. 2.1. Component level DTCs, such as sensor DTCs, solenoid DTCs, and relay DTCs.
    2.2.  System level DTCs, such as misfire DTCs, evaporative emission (EVAP) system DTCs, and fuel trim DTCs.

Advance to the List All DTCs screen on the scan tool.

Does the scan tool display any DTCs?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 8

8

Is the customers concern with inspection/maintenance (I/M) testing?

Go to Inspection/Maintenance (I/M) System Check in Engine Controls - 3.5L (LX9)

Go to Symptoms - Vehicle