There are two methods for obtaining or reading the diagnostic trouble codes from the vehicles covered in this information guide: with a Diagnostic Readout Box (DRB or DRBII) or the equivalent type of scan tool, or with the CHECK ENGINE light, located in the instrument panel. Both methods will be covered in the following sections.
DIAGNOSTIC READOUT BOX (DRB or DRBII)
See Figures 1, 2 and 3
Make sure to follow the manufacturer's instructions when using a scan tool.
- Attach the DRBII scan tool , or equivalent, to the data link connector located in the engine compartment near the powertrain control module (an L shaped connector with 8 terminals-refer to the engine compartment component location illustrations earlier in this section).
- Start the engine, if possible, cycle the transaxle selector and the A/C switch (if applicable). Shut the engine OFF .
- Turn the ignition switch ON , access Read Fault Screen. Record all of the fault messages shown on the DRBII or other scan tool. Observe the malfunction indicator lamp (CHECK ENGINE lamp on the instrument panel). The lamp should light for 3 seconds, then go out (bulb check).
State Display Test Mode
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 DRBII scan tool, or equivalent, to the vehicle (data link connector). 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 DRBII scan tool, or the equivalent, to the vehicle (data link connector) 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 DRBII 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
The early Premier and Monaco vehicles can only have their fault codes read by a scan tool.
The CHECK ENGINE light has 2 modes of operation: diagnostic mode and switch test mode. If a DRB II diagnostic tester is not available, the SBEC can show the technician fault codes by flashing the CHECK ENGINE light on the instrument panel in the diagnostic mode. In the switch test mode, after all codes are displayed, switch function can be confirmed. The light will turn on and off when a switch is turned ON and OFF. Even though the light can be used as a diagnostic tool, it has the following restrictions:
Be advised that the CHECK ENGINE light can only perform a limited amount of functions and it is a good idea to have the system checked with a scan tool to double-check the circuit function.Reading the CHECK ENGINE Light
The "CHECK ENGINE'' lamp has two modes of operation. They are as follows:
Diagnostic Mode-The SBEC can show fault codes by means of flashing the check engine lamp on the instrument cluster. To activate this function turn the ignition key on-off-on-off-on within five seconds. The check engine lamp will then come on for two seconds as a bulb check. Immediately following this it will display a fault code by flashing on and off. There is a short pause between flashes and a longer pause between digits. All codes displayed are two digit numbers with a four second pause between codes. An example of a code is as follows:
- Lamp on for two seconds, then turns off-lamp check.
- Lamp flashes 5 times, pauses, and then flashes once-code 51.
- Lamp pauses for four seconds, flashes five times, pauses and then flashes five times-code 55.
The two codes are 51 and 55. Any number of codes can be displayed as long as they are in memory. The lamp will flash until all of them are displayed.
- Switch Test Mode-After all codes are displayed, switch function can be verified. The lamp will turn on or off when a switch is turned on or off.
After the component failure has been repaired, the engine computer will erase the fault codes after 50-100 ON/OFF turns of the ignition key.