The Diagnostic Executive

The Diagnostic Executive
The Diagnostic Executive is a unique segment of software which is designed to coordinate and prioritize the diagnostic procedures as well as define the protocol for recording and displaying their results. The main responsibilities of the Diagnostic Executive are listed as follows:
- Commanding the check engine lamp on and off
- DTC logging and clearing
- Current status information on each diagnostic

Diagnostic Information
The diagnostic charts and functional checks are designed to locate a faulty circuit or component through a process of logical decisions. The charts are prepared with the requirement that the vehicle functioned correctly at the time of assembly and that there are not multiple faults present.

There is a continuous self-diagnosis on certain control functions. This diagnostic capability is complemented by the diagnostic procedures contained in this manual.

The language of communicating the source of the malfunction is a system of diagnostic trouble codes.

When a malfunction is detected by the control module, a diagnostic trouble code is set and the check engine lamp is illuminated.

Check Engine Lamp
The check engine lamp looks the same as the check engine lamp you are already familiar with, the Check Engine lamp.

Basically, the check engine lamp is turned on when the ECM detects a DTC that will impact the vehicle emissions.
- When the check engine lamp remains on while the engine is running, or when a malfunction is suspected due to a driveability or emissions problem, a Powertrain On-Board Diagnostic (OBD-II) System Check must be performed. The procedures for these checks are given in On-Board Diagnostic (OBD-II) System Check. These checks will expose faults which may not be detected if other diagnostics are performed first.

Data Link Connector (DLC)




The provision for communication with the control module is the Data Link Connector (DLC). It is located behind the lower front instrument panel. The DLC is used to connect to a Tech 2. Some common uses of the Tech 2 are listed:
- Identifying stored Diagnostic Trouble Codes (DTCs).
- Clearing DTCs.
- Reading serial data.