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 (12\text{V}) for at least 300\text{ ms} (T_{\text{idle}}).
- Key Bytes:
0xEAand0x8Fdesignate standard Keyword 2000 with physical addressing and normal timing parameters.
- Key Bytes:
- Wakeup Low Pulse (T_{\text{iniL}}): The tester pulls the K-Line low (0\text{V}) for exactly 25.0\text{ ms} \pm 1.0\text{ ms}.
- Line Recovery High Pulse (T_{\text{wup}}): The tester releases the K-Line high for 25.0\text{ ms} \pm 1.0\text{ ms}.
- Tester Start Communication Request (Service
$81): The tester transmits the 4-byte KWP2000 initialization telegram at 10,400\text{ bps} (8\text{N}1): \mathbf{\text{Telegram: } [0\text{x}81, \ 0\text{x}11, \ 0\text{x}F1, \ 0\text{x}81, \ 0\text{x}04]} - ECU Positive Response (Service
$C1): Within 20\text{ ms} to 50\text{ ms}, the ECU returns: \mathbf{[0\text{x}83, \ 0\text{x}F1, \ 0\text{x}11, \ 0\text{xC1}, \ 0\text{xEA}, \ 0\text{x8F}, \ 0\text{x7F}]}
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\text{ bps}, ME7.5 bootloaders support dynamic baud rate escalation via Service $87 (AccessTimingParameters) or Bosch proprietary switching sequences:
- 38,400\text{ bps}: Maximum reliable rate across noisy vehicle wiring or unshielded OBD cables.
- 57,600\text{ bps}: Standard high-speed bench flashing rate.
- 125,000\text{ bps}: Maximum hardware rate supported by the internal C167CR Asynchronous Serial Channel 0 (
ASC0) using a 20\text{ MHz} CPU crystal.