Detroit Diesel: Diagnostic Trouble Codes

Detroit Diesel Electronic Controls II (DDEC II)

Using Check Engine Lamp

  1. Place ignition switch in Off position.

  2. Connect a suitable jumper wire between terminals A and M of the DDL 12 pin connector. The DDL connector is typically located in the cab.

  3. Place ignition switch in On position and note codes being flashed out by the check engine lamp.

Using Diagnostic Data Reader

Follow Diagnostic Data Reader, or equivalent scan tool, instructions.

Detroit Diesel Electronic Controls III (DDEC III)

Using Check Engine Lamp

  1. Place ignition switch in On position.

  2. Depress and hold the diagnostic request switch.

  3. Note the check engine lamp flash codes.

Using Diagnostic Data Reader

Follow Diagnostic Data Reader, or equivalent scan tool, instructions.

Diagnostic Trouble Code Interpretation

Detroit Diesel Electronic Controls (DDEC II)

Using Check Engine Lamp

The diagnostic trouble codes will be displayed by the check engine lamp as long as jumper wire is connected between DDL terminals A and M and the ignition switch is in the On position. For example, a code 32 will be displayed by the check engine lamp flashing 3 times, followed by a 1/2 second pause, then 2 flashes. There is a 3 second pause between diagnostic flash codes.

Using Diagnostic Data Reader

Diagnostic trouble codes will be displayed on the Diagnostic Data Reader, or equivalent scan tool, screen.

Detroit Diesel Electronic Controls (DDEC III)

Using Check Engine Lamp

The diagnostic trouble codes will be displayed by the check engine lamp. For example, a code 32 will be displayed by the check engine lamp flashing 3 times, followed by a 1/2 second pause, then 2 flashes. There is a 3 second pause between diagnostic flash codes.

Using Diagnostic Data Reader

Diagnostic trouble codes will be displayed on the Diagnostic Data Reader, or equivalent scan tool, screen.