CAN docs: OBD-II is on the K-line via the ELM; nothing transmits on CAN

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

docs/impl/plans/CAN-BITRATE.md

@@ -28,8 +28,9 @@ Persisted (boot and hot-plug):
 (svc-core), the single writer: the adapter now acknowledges frames like any scan tool. To go back, set
 `CAN_OPTS="listen-only on restart-ms 100"` there and replug the PEAK (or restart `can-up@can_pcan`).
 
-obd-poller is **disabled since 2026-10-13**: the Z27AG's ECU never answered OBD-II on CAN (most likely K-line, pin 7,
-not wired). The adapter was left acknowledging anyway, as harmless at the measured bitrate.
+The Z27AG's ECU never answered OBD-II on CAN: it speaks ISO 9141-2 on the K-line (pin 7), confirmed through an ELM327
+on 2026-10-13. obd-poller now polls through that ELM over Bluetooth, so **nothing transmits on CAN**. The adapter was left
+acknowledging anyway, as harmless at the measured bitrate.
 
 ## Goal
 
@@ -57,7 +58,7 @@ Not set yet on purpose: no persistent bitrate until it's measured.
 
 **If every rate shows 0 frames:** the OBD port is probably behind a gateway that stays silent unless queried. Then the bitrate has to be found
 by sending one standard OBD-II request (ISO 15765-4: try 500k, then 250k), e.g. mode 01 PID 00 to `0x7DF`. That's transmitting, so it
-belongs to the single CAN writer (`obd-poller`, project-yukart decision 3). Do it deliberately, not as part of a sniff.
+belongs to the single writer (`obd-poller`, project-yukart decision 3). Do it deliberately, not as part of a sniff.
 
 ## After the rate is known