Home
Up

ALDL Mode 0 Data Stream

  Last Updated 31 May 2000

As far as I can tell, the Mode 0 data stream never contains any useable information, and is only used to 'wake up' the ECU.  To wake up the ECU, the ignition must be turned on. The ECU will remain 'awake' for approximatley 5 minuites after the ignition is turned off again. Once the ECU is woken up, any of  the other ALDL Mode commands can be used. If the user issues an ALDL command without having first woken up the ECU, then the ECU will ignore the request, and respond with a Mode 0 command of its own.

Request Mode 0 Data   - PC transmit to ECU

Data Byte (hex) Description Notes
F4 Frame Start 0xF4 indicates the start of a message
56 Length of Packet 0x56 (0x52 + Length of Packet)
00 Request Mode 0 0x00
B6 Checksum Packet added together then MOD 255 = 00

Reply Mode 0 Data - ECU transmit to PC

Once the ECU has received the Request Mode 0 Data packet (or any other valid Mode command packet if the ECU is not woken up first), it will respond (within a mili-second) with an identical Mode 00 packet.

Data Byte (hex) Description Notes
F4 Frame Start 0xF4 indicates the start of a message
56 Length of Packet 0x56 (0x52 + Length of Packet)
00 Request Mode 0 0x00
B6 Checksum Packet added together then MOD 255 = 00