There are two methods for obtaining or reading the diagnostic trouble codes from the vehicles covered in this guide: with a Diagnostic Readout Box (DRB III) or the equivalent type of scan tool, or with the MIL light, located in the instrument panel. Both methods will be covered in the following sections.
DIAGNOSTIC READOUT BOX (DRB III)
Make sure to follow the manufacturer's instructions when using a scan tool.
- Attach the DRB III scan tool, or equivalent, to the data link connector located in the passengers compartment at the lower edge of the instrument panel near the steering column.
- Turn the ignition switch ON , and access the Read Fault Screen. Record all of the fault messages shown on the DRB III or other scan tool.
The switch inputs used by the PCM have only 2 recognized states, high and low. For this reason, the PCM cannot recognize the difference between a selected switch position versus an open circuit, a short circuit, or a defective switch. If the change is displayed, it can be assumed that the entire switch circuit to the PCM is functional. From the state display screen access either State Display Inputs and Outputs or State Display Sensors.STATE DISPLAY INPUTS AND OUTPUTS
Connect the DRB III scan tool, or equivalent, to the vehicle data link connector (DLC). Access the State Display screen, then access Inputs and Outputs. Select one of the engine control system functions displayed in the Input and Output screen.STATE DISPLAY SENSORS
Connect the DRB III scan tool, or the equivalent, to the vehicle data link connector (DLC) and access the State Display screen. Access the Sensor Display and select one of the engine control system functions available in this window.Circuit Actuation Test Mode
The circuit actuation test mode checks for proper operation of output circuits or devices which the PCM cannot internally recognize. The PCM can attempt to activate these outputs and allow an observer to verify proper operation. Most of the tests provide an audible or visual indication of device operation (click of relay contacts, spray fuel, etc.). Except for intermittent conditions, if a device functions properly during testing, assume the device, its associated wiring and the driver circuit are working correctly.OBTAINING CIRCUIT ACTUATION TEST
Connect the DRB III scan tool , or the equivalent, to the vehicle and access the Actuators screen. Select one of the numerous engine control system functions accessible through this screen.
CHECK ENGINE LIGHT (MIL)
- Cycle the ignition key to ON , OFF , ON , OFF , ON within 5 seconds.
- Count the number of times the MIL (check engine light) on the instrument panel flashes on and off. The number of flashes represents the trouble code. There is a slight pause between the flashes representing the first and second digits of the code. Longer pauses separate the individual two digit trouble code.
An example of a flashed DTC is as follows: