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Professional 909 User Manual
illuminated Malfunction Indicator Lamp (MIL), check monitor status prior to
emissions certification testing, verify repairs, and perform a number of other
services that are emission-related.
After the tool is properly connected to the vehicle’s DLC, tap “OBD II” on the
Job menu. The tool will automatically start a check of the vehicle’s computer
to determine which type of communication protocol it is using. When the tool
identifies the computer’s communication protocol, a communication link is
established and then the screen will display the Monitor Status.
Fig. 5-12
Note: A PROTOCOL is a set of rules and procedures for regulating data
transmission between computers, and between testing equipment and computers.
Now five different types of protocols (ISO 9141, Keyword 2000, J1850 PWM, J1850
VPW and CAN) are in use by vehicle manufacturers.
Tap “OK”, the following function list appears.
1. Read Codes
This option is used to identify which section of the emission control system has
malfunctioned.
*Note: Diagnostic Trouble Codes or Fault Codes can be used to identify which engine
systems or components that are malfunctioning. Never replace a part based only on
the DTC definition. Retrieving and using DTCs for troubleshooting vehicle operation is
only one part of an overall diagnostic strategy. Follow testing procedures (in vehicle’s
service manual), instructions and flowcharts to confirm the locations of the problem.
2. Erase Codes
After reading the retrieved codes from the vehicle and certain repairs have been
carried out, you can use this function to erase the codes from the vehicle. Before
