DoCAN vs. OBD-II Connector
Comparing 2 standards across 13 specifications. 13 key differences identified.
Diagnostics on CAN (DoCAN, standardized under ISO 15765-2 and ISO 15765-4) is the network and transport layer protocol that enables diagnostic protocols (such as UDS ISO 14229 and OBD-II ISO 15031) to transmit multi-byte messages (up to 4095 bytes) over 8-byte CAN bus frames. Managing packet segmentation, Flow Control handshakes, and block sizes.
The SAE J1962 Connector (standardized under ISO 15031-3, commonly called the OBD-II Data Link Connector / DLC) is the mandatory 16-pin trapezoidal diagnostic interface installed in passenger vehicles since 1996. Located within 2 feet of the steering column, it provides standard battery power, grounds, and multi-protocol network lines (CAN Bus, K-Line, KWP2000, J1850).
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standardization
|
ISO 15765-2 (ISO-TP Network Layer) / ISO 15765-4 (Emissions CAN) | SAE J1962 / ISO 15031-3 / EOBD (Europe) / JOBD (Japan) |
|
Maximum Message Length
|
Up to 4,095 bytes (segmented across multiple sequential 8-byte CAN frames) | — |
|
Single Frame (SF–PCI 0x0_)
|
Used when total payload fits in a single frame (up to 7 bytes in Classic CAN; byte 0 indicates data length) | — |
|
First Frame (FF–PCI 0x1_)
|
First frame of a segmented message; bytes 0-1 encode the total 12-bit message length (e.g. 0x10 0x80 = 128 bytes) | — |
|
Flow Control Frame (FC–PCI 0x3_)
|
Receiver sends Flow Status (Clear to Send), Block Size (BS), and Separation Time (STmin) pacing inter-frame delays | — |
|
Consecutive Frame (CF–PCI 0x2_)
|
Transmits remaining data with a 4-bit rolling Sequence Number (0 to 15) to detect dropped packets | — |
|
Emissions OBD Request IDs
|
Standard 11-bit functional broadcast ID: 0x7DF | Standard response IDs: 0x7E8 (Engine ECM), 0x7E9 (TCM) | — |
|
Pin 4 & Pin 5 (Grounds)
|
— | Pin 4: Chassis Ground | Pin 5: Signal / Sensor Ground |
|
Pin 16 (Battery Power)
|
— | Unswitched permanent +12V (or +24V) battery power from vehicle fuse block (max 4A continuous) |
|
Pin 6 & Pin 14 (ISO 15765-4 CAN)
|
— | Pin 6: CAN High (CAN_H, 2.5V to 3.5V) | Pin 14: CAN Low (CAN_L, 2.5V to 1.5V) |
|
Pin 7 & Pin 15 (ISO 9141-2 / KWP2000)
|
— | Pin 7: K-Line single-wire serial data | Pin 15: L-Line initialization line |
|
Pin 2 & Pin 10 (SAE J1850)
|
— | Pin 2: J1850 VPW (+7V GM bus) / PWM (+) | Pin 10: J1850 PWM (-) (Ford 41.6 kbps) |
|
Type A vs Type B Keying
|
— | Type A (12V passenger cars: uninterrupted center alignment tab) vs Type B (24V commercial: split center tab prevents 12V scanner burnout) |