J2534 log format v2

Last modified: January 10, 2026

Overview

The J2534 library uses a compact, easily parseable log format. Each line represents a single operation or data message. The format is optimized for automated analysis and allows the full sequence of actions during vehicle diagnostics to be reconstructed.

Log file structure

# v2 2026-01-10 02:00:18
  0 I j0 open 192.168.12.3 > ok 4ms
 10 I j0 conn ISO15765 500000 > 1 9ms
  6 I j0 wr 1 100 1 > 1 5ms
	[6A8]10C0 0.000 2
  5 I j0 rd 1 2000 10 > 1 4ms
	[688]61C0 2240.300 2
...

Header: # v2 YYYY-MM-DD HH:MM:SS (format version, session start date and time)
Delta time: milliseconds since the previous operation (3 characters, right-aligned; values >999 extend to the left)
Log level: I (Info), E (Error), W (Warning), D (Debug)
Data lines: indented by a tab character (no blank lines are used)

Application entries

The application can add its own entries to the log via the PassThruWriteToLog function:

  0 I pt_lib open param: 192.168.12.3, type:1
  0 I pt_lib open param: 192.168.12.3, name:sd0;n192.168.12.3

Application entries use the identifier pt_lib instead of a device number.

Operation line format

DELTA LEVEL DEVICE COMMAND PARAMS > RESULT DURATION

  0 I j0 open 192.168.12.3 > ok 4ms
 10 I j0 conn ISO15765 500000 > 1 9ms
  5 I j0 disc 1 > ok 4ms
  4 I j0 close > ok 3ms

Position	Field	Description
0	DELTA	Delta time in milliseconds from the previous operation (3 characters, right-aligned)
1	LEVEL	Log level: I (Info), E (Error), W (Warning), D (Debug)
2	DEVICE	Device number (j0, j1, ... j15) or pt_lib for application entries
3	COMMAND	Command name
4+	PARAMS	Input parameters (see command table below)
-	>	Separator
-2	RESULT	Result / output values
-1	DURATION	Operation duration (Nms)

Data line format

  [CAN_ID]DATA TIMESTAMP LEN FLAGS

Position	Field	Description
-	\t	Tab indentation
0	[CAN_ID]	CAN identifier in square brackets
1	DATA	Data bytes (hex, no spaces). Empty if LEN=0
2	TIMESTAMP	Device timestamp in seconds.milliseconds (SSSS.mmm)
3	LEN	Data length in bytes
4	FLAGS	Flags separated by the \| character (optional)

If the protocol differs from the channel protocol, it is added to FLAGS.

Examples:

  [688]61B05646375244 2240.300 8
  [688]61B05646375244 2240.300 8 RX_START
  [6A8] 2240.281 0 INT|TX_DONE
  [612:F1]037F2212 2240.300 4 CAN
  [612:F1]037F2212 2240.300 4 INT|CAN

Result codes

Result	Description
ok	Success (STATUS_NOERROR)
N	Actual number of messages read/written 0 = buffer empty (instead of the text error code ERR_BUFFER_EMPTY; not an error) Less than requested = timeout elapsed (instead of the text error code ERR_TIMEOUT; not an error)
ERR_XXX	Text error code ERR_XXX = operation failed (ERR_INVALID_CHANNEL_ID, ERR_DEVICE_NOT_CONNECTED, etc.)
"text"	Quoted text string (e.g., the description of the last error returned by the PassThruGetLastError call)

Command reference

Connection and session management

Command	Parameters (positions 3+)	Result	Description
open	address	ok/ERR	Open connection to device
close	-	ok/ERR	Close connection
conn	protocol baud	channel	Connect a channel using the specified protocol
disc	channel	ok/ERR	Disconnect a channel

Connection types:

LAN: 192.168.12.3 (IP address)
BLE: bN4999 (b + device name prefix)

Reading and writing messages

Command	Parameters	Result	Description
rd	channel timeout num	num or ERR	Read messages
wr	channel timeout num	num or ERR	Write messages

Parameters:

channel - Channel ID from the conn command
timeout - Timeout in milliseconds
num - Number of messages

Result:

A number. The actual number of messages read/written.
Text error code ERR_XXX.

Log level for rd:

I - Successful read (requested number of messages received)
W - Buffer empty (0 messages) or timeout (fewer than requested received)
E - Error (ERR_XXX)

 26 I j0 wr 1 100 1 > 1 6ms
	[6A8]10C0 0.000 2
  6 I j0 rd 1 2000 10 > 10 5ms
	[6A8] 2240.281 0 INT|TX_DONE
	[688] 2240.294 0 RX_START
 15 W j0 rd 1 0 10 > 0 2ms
 62 W j0 rd 1 50 10 > 2 62ms
	[7DF] 2.489 0 INT|TX_DONE
	[7E8]4100BE1FA813 2.489 6
 41 E j0 rd 1 2000 10 > ERR_INVALID_CHANNEL_ID 0ms

Filters

Command	Parameters	Result	Description
flt+	channel [protocol] type mask pattern [flow]	filter_id	Set a filter
flt-	channel filter_id	ok/ERR	Remove a filter

Parameters:

channel - Channel ID
protocol - Protocol name (optional, specified if different from the channel protocol)
type - Filter type (PASS, BLOCK, FLOW)
mask - Filter mask (hex)
pattern - Filter pattern (hex)
flow - Flow Control ID for FLOW filters (hex)

Filter types:

PASS - Pass filter (allow matching messages)
BLOCK - Block filter (reject matching messages)
FLOW - Flow control filter (ISO15765)

 13 I j0 flt+ 1 FLOW FFFFFFFF 688 6A8 > 0 3ms
  3 I j0 flt+ 1 ISO15765 FLOW FFFFFFFF 000007E8 000007E0 > 0 0ms
139 I j0 flt- 1 0 > ok 3ms

Periodic messages

Command	Parameters	Result	Description
per+	channel interval	msg_id	Start a periodic message
per-	channel msg_id	ok/ERR	Stop a periodic message

Parameters:

interval - Message interval in milliseconds
msg_id - Periodic message ID (returned by per+, used by per-)

 50 I j0 per+ 1 100 > 0 5ms
	[6A8]3E00 0.000 2
150 I j0 per- 1 0 > ok 3ms

The data line after per+ shows the content of the periodic message (same format as for wr).

IOCTL commands

Command	Parameters	Result	Description
io	channel ioctl_id [params]	[result]	IOCTL operation

GET_CONFIG - Read protocol configuration parameters

DELTA LEVEL DEVICE io channel GET_CONFIG > PARAM:value|PARAM:value|... Nms

Example:

200 I j0 io 1 GET_CONFIG > P2_CAN:2000|P3_MIN:45|ISO15765_BS:8 8ms

SET_CONFIG - Set protocol configuration parameters

DELTA LEVEL DEVICE io channel SET_CONFIG PARAM:value|PARAM:value|... > ok Nms

Example:

 10 I j0 io 1 SET_CONFIG P2_CAN:2000|P3_MIN:45|ISO15765_WFT_MAX:0 > ok 10ms

Common parameters: DATA_RATE, LOOPBACK, P1_MAX, P3_MIN, P4_MIN, W0-W5, TIDLE, TWUP, PARITY, ISO15765_BS, ISO15765_STMIN, BS_TX, STMIN_TX, ISO15765_WFT_MAX, ISO15765_PAD_VALUE, J1962_PINS, CAN_MIXED_FORMAT, FD_CAN_DATA_PHASE_RATE, HS_CAN_TERMINATION, N_CR_MAX and others.

READ_VBATT - Read battery voltage (pin 16)

DELTA LEVEL DEVICE io 0 READ_VBATT > voltage Nms

Result: Voltage in X.X format (volts with one decimal place).

Example:

 10 I j0 io 0 READ_VBATT > 12.3 5ms

READ_PIN_V - Read voltage on a specific pin of the J1962 connector

DELTA LEVEL DEVICE io 0 READ_PIN_V pin > voltage Nms

Parameters:

pin - Pin number (1-16, except 4 and 5 which are ground)

Examples:

 10 I j0 io 0 READ_PIN_V 16 > 12.3 5ms

5BAUD_INIT - 5-baud initialization for ISO9141/ISO14230

DELTA LEVEL DEVICE io channel 5BAUD_INIT in_addr > out_keybytes Nms

Parameters:

in_addr - Input address byte(s) (hex)
out_keybytes - Output key bytes (hex, typically 2 bytes)

Example:

 30 I j0 io 1 5BAUD_INIT 33 > 8F6F 2850ms

FAST_INIT - Fast initialization for ISO14230 (KWP2000)

DELTA LEVEL DEVICE io channel FAST_INIT [tx_msg] > [rx_msg] Nms

Parameters (optional):

tx_msg - Transmitted wake-up message (hex)
rx_msg - Received response message (hex)

Examples:

 10 I j0 io 1 FAST_INIT 8121F181 > 83F11061 85ms
 10 I j0 io 1 FAST_INIT > ok 75ms

Buffer clear commands

DELTA LEVEL DEVICE io channel IOCTL_NAME > ok Nms

Command	Description
CLEAR_TX_BUFFER	Clear TX buffer
CLEAR_RX_BUFFER	Clear RX buffer
CLEAR_PERIODIC_MSGS	Clear periodic messages
CLEAR_MSG_FILTERS	Clear message filters
CLEAR_FUNCT_MSG_LOOKUP_TABLE	Clear the functional message lookup table

Example:

 10 I j0 io 1 CLEAR_RX_BUFFER > ok 2ms
 10 I j0 io 1 CLEAR_MSG_FILTERS > ok 3ms

REQ_CONN - TP2.0 connection request

DELTA LEVEL DEVICE io channel REQ_CONN addr > ok Nms

Parameters: addr - Logical address (hex)

Example:

 10 I j0 io 1 REQ_CONN 01 > ok 150ms

Other commands

Command	Parameters	Result	Description
ver	-	fw dll api	Read DLL version
rd_ver	-	ver:FW:XX;HW:XXXXXXXX;SN:X	Read device firmware version
volt	pin voltage	ok/ERR	Set programming voltage
err	-	error_text	Get the description of the last error

Examples:

  0 I j0 rd_ver > ver:FW:81;HW:0000FF05;SN:0 16ms
300 I j0 err > "Channel not connected" 0ms

CAN ID format

Type	Format	Example
11-bit standard	[XXX]	[612]
29-bit extended	[XXXXXXXX]	[18DA00F1]
11-bit + extended address	[XXX:XX]	[612:F1]
29-bit + extended address	[XXXXXXXX:XX]	[18DA00F1:F1]

The extended address is shown when the EXT_ADDR flag is set.

Flags reference

Receive (RX) flags

Flag	Bit	Description
INT	0	Internal/loopback (TX_MSG_TYPE). 1 = echo from adapter, 0 = from the bus
RX_START	1	Start of a segmented message (START_OF_MESSAGE)
RX_BREAK	2	Link break detected (RX_BREAK)
TX_DONE	3	Transmission completed successfully (TX_SUCCESS)
TX_FAIL	9	Transmission error (TX_FAILED)
PAD_ERR	4	ISO15765 padding error (ISO15765_PADDING_ERROR)
EXT_ADDR	7	Extended addressing mode (ISO15765_ADDR_TYPE)
EXT29	8	29-bit CAN ID (CAN_29BIT_ID)
FD	20	CAN FD frame (FD_CAN_FORMAT)
BRS	19	CAN FD bit rate switch (FD_CAN_BRS)
ESI	21	CAN FD error state indicator (FD_CAN_ESI)

Transmit (TX) flags

Flag	Bit	Description
NO_DONE	0	Do not wait for TX acknowledgment (ISO15765_NO_TXDONE)
NO_RESP	1	Do not wait for a response (ISO15765_NO_RESP)
PAD	6	Use ISO15765 padding (ISO15765_FRAME_PAD)
EXT_ADDR	7	Extended addressing mode (ISO15765_ADDR_TYPE)
EXT29	8	Use 29-bit CAN ID (CAN_29BIT_ID)
P3_ONLY	9	Wait only for P3 min (WAIT_P3_MIN_ONLY)
SW_HV	10	SW-CAN high-voltage transmission (SW_CAN_HV_TX)
FD	20	CAN FD frame (FD_CAN_FORMAT)
BRS	19	CAN FD bit rate switch (FD_CAN_BRS)

Supported protocols

Name	Protocol ID	Description
CAN	5	Raw CAN
ISO15765	6	ISO 15765-2 (CAN transport)
ISO9141	3	ISO 9141-2 (K-Line)
ISO14230	4	ISO 14230 (KWP2000)
J1850VPW	1	J1850 VPW
J1850PWM	2	J1850 PWM
FD_CAN	0x8011	CAN FD
FD_ISO15765	0x8012	ISO 15765 over CAN FD

For the full list of protocols, see the SAE J2534-1 and J2534-2 specifications.

Full log example

# v2 2026-01-10 02:00:18
  0 I j0 open 192.168.12.3 > ok 4ms
  7 I j0 conn ISO15765_PS 500000 > 1 6ms
  6 I j0 flt+ 1 FLOW FFFFFFFF 688 6A8 > 0 3ms
  4 I j0 io 1 SET_CONFIG J1962_PINS:0308 > ok 8ms
  9 I j0 wr 1 100 1 > 1 6ms
	[6A8]21B0 0.000 2
  6 I j0 rd 1 2000 10 > 2 5ms
	[6A8] 2240.281 0 INT|TX_DONE
	[688] 2240.294 0 RX_START
  5 I j0 rd 1 2000 10 > 1 12ms
	[688]61B0564637524452464A46394C353632303836 2240.300 23
 20 I j0 wr 1 0 1 > 1 2ms
	[6A8]1081 0.000 2
 50 I j0 rd 1 2000 10 > 2 48ms
	[6A8] 2240.350 0 INT|TX_DONE
	[688]5081 2240.355 2
 40 I j0 io 1 CLEAR_RX_BUFFER > ok 2ms
  8 I j0 flt- 1 0 > ok 3ms
  9 I j0 disc 1 > ok 4ms
  4 I j0 close > ok 3ms

Reading the log

j0 open 192.168.12.3 - Open a LAN connection
j0 conn ISO15765_PS 500000 > 1 - Connect an ISO15765_PS channel, channel_id=1 obtained
j0 flt+ 1 FLOW ... - Set a flow control filter
j0 io 1 SET_CONFIG - Set protocol parameters (connect to pins 3 and 8)
j0 wr 1 100 1 - Write 1 message, 100 ms timeout, on channel 1
- [6A8]21B0 - CAN ID 6A8, request identification data with command 21B0
j0 rd 1 2000 10 > 2 - Read up to 10 messages, 2 received (ERR_TIMEOUT occurred but is not shown)
- [6A8] ... INT|TX_DONE - adapter response | transmission completed (successful transmission notifications arrive with no data, len=0)
- [688] ... RX_START - Start of a segmented response
j0 rd ... > 1 - Read, 1 message received
- [688]61B0... - Response data, 23 bytes
j0 io 1 CLEAR_RX_BUFFER - Clear the RX buffer
Continue with flt-, disc, close

Developer tips

Use the tab character to identify data lines (only they are indented)
The > separator clearly divides input parameters and results
Timestamps allow performance and timeouts to be analyzed
All data is in hex format (without the 0x prefix) for compactness
Log files can be used for replaying and debugging diagnostic sessions

Note: The v2 format is not backward-compatible with v1. Check the log header to determine the version.