CHAPTER 49 On-Board Diagnostics

Retrieving and Recording DTCs, OBD Monitor Status, and Freeze-Frame Data 49-1 Select the scan tool to provide the best coverage for the type and make of vehicle. Locate the DLC and connect the scan tool.

Retrieving and Recording DTCs, OBD Monitor Status, and Freeze-Frame Data 49-1 Power on the scan tool, and turn the ignition on. Establish scan tool communications with the vehicle.

Retrieving and Recording DTCs, OBD Monitor Status, and Freeze-Frame Data 49-1 Retrieve and record the DTCs.

Retrieving and Recording DTCs, OBD Monitor Status, and Freeze-Frame Data 49-1 Retrieve and record OBD monitor status.

Retrieving and Recording DTCs, OBD Monitor Status, and Freeze-Frame Data 49-1 Retrieve and record freeze-frame data applicable to DTCs and monitors.

Retrieving and Recording DTCs, OBD Monitor Status, and Freeze-Frame Data 49-1 Power off the scan tool, turn the ignition off, and disconnect the scan tool.

49-2 Locate the DLC and connect the scan tool. Diagnosing Drivability or Emission Concerns When There Are Stored or Active DTCs Present, and to Obtain and Interpret Scan Tool Data 49-2 Locate the DLC and connect the scan tool. Power on the scan tool, and turn the ignition on. Establish scan tool communications with the vehicle. Retrieve and record DTCs. Look up DTC definitions in code books or the manufacturer's information. Interpret results with reference to the manufacturer's information. Diagnose drivability or emission concerns, and identify and recommend a course of action for repair. Power off the scan tool, turn ignition off, and disconnect the scan tool.

Testing Engine Control System Sensors, the PCM, Actuators, and Circuits 49-3 Determine the circuit to be tested and the likely voltages and frequency of the waveform to be measured. Set up the graphing multimeter or oscilloscope, setting the voltage level and time base to commence measurements.

Testing Engine Control System Sensors, the PCM, Actuators, and Circuits 49-3 Connect the leads to the points to be measured.

Testing Engine Control System Sensors, the PCM, Actuators, and Circuits 49-3 Capture the waveforms from the circuit under test. Analyze the waveform, comparing it to the manufacturer's specifications or known good waveforms. Determine the necessary actions.

49-4 Verify the customer complaint and identify the symptoms. Diagnose Drivability and Emission Problems Resulting from Malfunctions of Interrelated Systems 49-4 Verify the customer complaint and identify the symptoms. Plan diagnostic tests on interrelated systems with reference to the manufacturer's information. Use diagnostic test equipment to conduct tests. Interpret results with reference to the manufacturer's information. Diagnose drivability and emission problems resulting from malfunctions of interrelated systems, and recommend a course of action for repair.

To test actuators, follow the steps in 49-5 Reference the manufacturer's information, as necessary. Determine the actuators to be tested and the required operating parameters required for correct operation. Select the appropriate test equipment. Conduct actuator tests on and off the vehicle as required. Analyze the test results against the manufacturer's specifications, and make recommendations as required.

49-6 Locate the DLC and connect the scan tool. To interpret DTCs and scan tool data related to the emission control system, follow the steps in 49-6 Locate the DLC and connect the scan tool. Power on the scan tool, and turn the ignition on. Establish scan tool communications with the vehicle. Retrieve and record the DTCs. Look up the DTCs' definitions in code books or in the manufacturer's information. Interpret the results, referencing the manufacturer's information. Power off the scan tool, turn the ignition off, and disconnect the scan tool.