Understand OBD2 Monitor Status and Readiness
OBD CAN reads a small set of standard OBD2 monitor and trip counters to show what the vehicle reports about emissions-system self-checks. It presents support and readiness separately, and shows the monitor status since codes were cleared (Mode 01 PID 01) alongside the current drive-cycle status (PID 41), when the vehicle supplies both.
What to check
The screen requests PIDs 0x21, 0x30, 0x31, 0x01, and 0x41. Depending on vehicle support, these can include distance travelled with the MIL on, warm-ups and distance since codes were cleared, readiness status since clearing, and monitor status during the current drive cycle. Unsupported or unavailable items may have no value. The app shows available responses; it does not turn missing values into a pass.
Run and review the read
- Sign in and connect a compatible BLE OBD2 adapter.
- Open Monitor Status and choose Start Reading, or use refresh to request the values again.
- For each returned monitor, check whether it is supported and whether it is ready. Read the mode label so you know whether a status refers to since codes were cleared or only to the current drive cycle.
- Review the MIL-on distance, warm-up count, and distance-since-clear values as counters reported by the ECU. Copy or save the report image if you need to discuss it later; the history control can reopen saved readings.
Example: codes were recently cleared
If some emissions monitors still show “not ready” after a repair, compare the since-clear status with the current-cycle status and note the ECU’s distance and warm-up counters. The next step is to follow the vehicle maker’s prescribed drive cycle and recheck, or ask a repair professional to inspect it. A not-ready item means the self-test is incomplete, not necessarily that a part failed. Neither a ready status nor these counters alone guarantee an emissions inspection pass.
Do not confuse this with an inspection verdict
This screen reports raw OBD monitor state and related counters. A separate inspection precheck applies its own displayed rule to MIL, required monitors, and DTCs. A “ready” item here is not the same as an overall precheck pass or a tailpipe emissions result. Vehicle support and local inspection rules differ; check the official criteria for your area.
Access and frequently asked questions
Reading requires sign-in, a connected compatible BLE adapter, and paid membership. The adapter is sold separately; iOS does not support classic Bluetooth or Wi-Fi. Saved history is local to the device and account, not cloud-synchronized.
Why are some monitors not supported?
Support varies by vehicle; no response is not a failed test.
Does clearing codes make monitors ready?
No. The vehicle must rerun monitors after clearing codes.
Read the standard OBD2 full scan guide · Compare diagnostics and inspection precheck · Review saved reports