The 6260A code routine manages the ECU diagnostic LED output. The ECU firmware triggers the Check Engine Light (CEL) by writing specific hexadecimal values to memory address X2000 during diagnostic procedures.

Diagnostic Logic#

The firmware controls the diagnostic LED state through specific writes to the X2000 memory register. The LED behavior is determined by the following values:

• Value #16: Standard diagnostic flash sequence.
• Value #96: Alternative diagnostic flash sequence (dependent on specific ECU state).

Tip

Bench testing can be performed by modifying the firmware to write values other than #16 or #96 to X2000. This allows for the observation of other hardware lines that may toggle in response to these memory writes.

Experimental Procedure#

To identify additional output signals controlled by this routine, follow these steps:

1. Disassemble: Locate the diagnostic routine within the ECU firmware.
2. Modify: Replace the standard MOV instructions (writing #16 or #96) with custom values.
3. Monitor: Use a logic analyzer or oscilloscope on the ECU output pins to detect signal toggling during the execution of the modified code.