Roadmaster Estate Wagon V8-350 5.7L (1993)
Typical Scan Data Values
Circuit Description:
The On-Board Diagnostic (OBD) system check is an organized approach to identifying a problem created by an electronic engine control system
malfunction. It must be the starting point for any driveability complaint diagnosis, because it directs the service technician to the next logical step in
diagnosing the complaint. Understanding the chart and using it correctly will reduce diagnostic time and prevent the unnecessary replacement of good
parts.
Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1.
This step is a check for the proper operation of the Malfunction Indicator Lamp (MIL) "Service Engine Soon." The MIL should be "ON" steady.
2.
No MIL at this point indicates that there is a problem with the MIL circuit or the ECM control of that circuit.
3.
This test checks the ability of the ECM to control the MIL. With the diagnostic terminal grounded, the MIL should flash a DTC 12 three times,
followed by any DTC stored in memory.
4.
Most procedures use a scan tool to aid diagnosis, therefore, serial data must be available. If a PROM error is present, the ECM may have been able
