Appendix G of K
KWP2000 Timings, Services & Security Access
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5.7. KWP2000 Protocol Timings & Fast Initialization across ME7.5 Clusters
All Bosch ME7.5 engine control units utilize the ISO 14230-4 / KWP2000 (Keyword Protocol 2000) standard over a single bi-directional diagnostic line (Pin 43 / K-Line) conforming to ISO 9141-2 physical transceivers. When establishing communication for calibration extraction, datalogging, or high-speed reflashing, diagnostic tools must strictly observe the initialization sequence and inter-byte bus timings.
1. Fast Initialization Sequence (Fast Init)
Standard 5-baud initialization is deprecated on ME7.5 in favor of the Fast Initialization sequence:
- Line Idle: The tester holds the K-Line at passive pull-up (12V) for at least 300 ms (Tidle).
- Key Bytes:
0xEAand0x8Fdesignate standard Keyword 2000 with physical addressing and normal timing parameters.
- Key Bytes:
- Wakeup Low Pulse (TiniL): The tester pulls the K-Line low (0V) for exactly 25.0 ms ± 1.0 ms.
- Line Recovery High Pulse (Twup): The tester releases the K-Line high for 25.0 ms ± 1.0 ms.
- Tester Start Communication Request (Service
$81): The tester transmits the 4-byte KWP2000 initialization telegram at 10,400 bps (8N1): Telegram: [0x81, 0x11, 0xF1, 0x81, 0x04] - ECU Positive Response (Service
$C1): Within 20 ms to 50 ms, the ECU returns: [0x83, 0xF1, 0x11, 0xC1, 0xEA, 0x8F, 0x7F]
2. KWP2000 Inter-Byte & Inter-Message Timing Limits
BOSCH ME7.5 KWP2000 BUS TIMING SPECIFICATION
| Timing | Description | Minimum | Maximum | Default Value |
|---|---|---|---|---|
| P1 | Inter-byte time for ECU response | 0 ms | 20 ms | 0 ms |
| P2 | Time between Tester request & ECU reply | 25 ms | 50 ms | 25 ms |
| P3 | Time between ECU reply & next request | 55 ms | 5000 ms | 55 ms |
| P4 | Inter-byte time for Tester request | 0 ms | 20 ms | 0 ms |
3. High-Speed Baud Rate Negotiation
While standard diagnostics operate at 10,400 bps, ME7.5 bootloaders support dynamic baud rate escalation via Service $87 (AccessTimingParameters) or Bosch proprietary switching sequences:
- 38,400 bps: Maximum reliable rate across noisy vehicle wiring or unshielded OBD cables.
- 57,600 bps: Standard high-speed bench flashing rate.
- 125,000 bps: Maximum hardware rate supported by the internal C167CR Asynchronous Serial Channel 0 (
ASC0) using a 20 MHz CPU crystal.