Car health check

What the green, amber and red icon means

Every session you upload gets a quick engine-health read from the channels your logger or ECU already recorded — oil pressure, temperatures, knock, mixture, voltage, fuel pressure. This page lists every rule and every threshold, so you know exactly what the icon is and isn't telling you.

How the icon is decided Oil Temperatures Knock & mixture Voltage & fuel Info-only checks

Car OK

Every rule that could run passed on every timed lap.

Car: check

Something is drifting toward a limit. Worth a look before the next session.

Car: fault

A hard limit was crossed. Look at the flagged lap before you go back out.

Not checked

The session logs no engine channel the rules can use — GPS-only loggers land here. It is not a pass.

How the icon is decided

The check is a fixed set of rules, applied the same way to every session. No AI is involved and the rules never see anything but your own session's channels.

Rules run on timed laps only — the out-lap and in-lap are ignored, so a cold start or a cool-down doesn't count against you.
A rule needs at least 100 qualifying samples before it will say anything, pass or fail.
A missing channel makes that rule unchecked, never green. Green means "checked and fine", not "nothing found".
A channel that is flat for the whole session is ignored by every rule — a dead oil-pressure sender reading zero would otherwise be a hard red.
Roll-up: any red finding makes the icon red; otherwise any amber makes it amber; otherwise, if at least one rule ran, it's green; if none could, it's Not checked.
Each finding remembers which laps it fired on and the single worst moment. In the app, the lap list dots those laps and clicking the dot drops every cursor on that moment.

Units. Rules that compare a channel against itself don't need units. Absolute rules (the temperature and pressure ceilings) use the channel's label when it says psi, bar, kPa, °F or °C, and otherwise infer the unit from the magnitude of the readings — ECU-merged channels often arrive unlabelled. If the unit can't be read, that rule reports unchecked rather than guess.

This is a screen, not a diagnosis. The thresholds are deliberately conservative starting points calibrated on real track sessions so that red stays rare enough to be believed. Know your engine — a car that lives at 145 °C oil on purpose will show amber every session.

Oil

Oil pressure

Needs oil pressure and rpm

Level	Condition
Red	Below the floor — under 1.5 bar (≈ 22 psi) while above 4000 rpm, sustained for at least 0.3 s so a single glitched sample can't fire it.
Amber	Dips — above 3000 rpm, each reading is compared with the session's typical pressure at that rpm. Fires when the lowest 1 % of readings sit more than 40 % below typical.
Unchecked	The median above 4000 rpm is under 2.25 bar (the channel isn't reading real pressure — a running engine would have died), or 20 % or more of the hot readings are pinned at the channel's maximum (a clipped sensor).

Oil starvation under cornering load

Needs oil pressure and lateral G

Catches pickup uncovering in long corners. The lowest 5 % of rpm-normalised pressure while cornering hard (more than 1.0 g lateral) is divided by the lowest 5 % on the straights (under 0.3 g).

Level	Loaded ÷ straight
Amber	Below 0.80
Red	Below 0.65

Temperatures

Oil temperature

Needs oil temperature

Level	Condition
Red	Any single reading above 143 °C (290 °F), or above 150 °C sustained for 10 s.
Amber	Above 140 °C (284 °F) sustained for 30 s.

Calibrated on real sessions: 141–147 °C for under a minute is how several race cars run every lap, and 154 °C and up is the genuine outlier tail.

Coolant temperature

Needs coolant temperature

Level	Condition
Red	Any single reading above 110 °C (230 °F), or above 112 °C sustained for 10 s.
Amber	Above 105 °C (221 °F) sustained for 30 s.
Unchecked	The unit can't be read from the label or inferred from the readings.

Temperature still climbing

Needs oil temperature or coolant temperature, and at least 6 timed laps

A temperature that never plateaus is a cooling system that can't keep up, even if it hasn't hit a ceiling yet.

Level	Condition
Amber	Over the last 4 timed laps the per-lap average is rising by more than 3 °C per lap, and the last lap is already within 15 °C of that channel's amber ceiling.

Shorter sessions are treated as still warming up and skipped.

Knock & mixture

Knock

Needs a knock channel; counts only above 3000 rpm when rpm is present

ECUs log knock two ways, and the rule works out which it has. A counter only ever goes up, so events are the counter's advances — not every non-zero sample. A flag is 0 or 1 per sample.

Channel style	Amber	Red
Counter	10 or more events in the session	100 or more
Flag	Flagged on 3 % or more of samples	10 % or more

A "knock" channel that is non-zero on more than half its samples is a continuous sensor level, not a detection, and is reported unchecked. One ECU's flag fires on 0.7–4 % of samples as background, which is why the amber floor sits at 3 %.

Mixture at wide-open throttle

Needs lambda or AFR and throttle; wide-open = the top 10 % of your throttle channel's own range, above 3000 rpm

Level	Condition
Red	Lean — λ above 1.05 (AFR ≈ 15.4) sustained for 2 s at full throttle.
Amber	The full-throttle median sits outside λ 0.72–0.95 (AFR ≈ 10.6–14.0). Rich is only ever amber — that's a tuning preference, not a fault.
Unchecked	The full-throttle median is above λ 1.10 (a wideband sitting at its lean rail), or the channel's scale isn't recognisable as lambda or AFR.

AFR channels are converted at 14.7 : 1 (petrol) and the finding says so when it does.

Voltage & fuel

Charging / system voltage

Needs battery voltage; judged above 2000 rpm when rpm is present

Level	Condition
Red	Below 11.8 V sustained for 30 s.
Amber	Below 12.3 V sustained for 30 s. (An AiM logger's "external voltage" reads 0.3–0.5 V under the battery, which is allowed for.)
Amber	Falling through the session — over 3 or more laps, the first lap's average is more than 0.5 V above the last lap's, and the last lap sits under 13.0 V (the alternator isn't keeping up).
Unchecked	The median isn't a 12 V system (10–16 V). A 3.7–4.2 V "battery" is the logger's own internal cell.

Readings under 6 V are ignored — that's the logger's supply blinking, not the car's.

Fuel pressure droop

Needs fuel pressure; uses lateral G above 0.8 g as "loaded" when present

The lowest 5 % of pressure under load, divided by the session median. Catches a pump or pickup that can't hold pressure in long corners.

Level	Loaded ÷ median
Amber	Below 0.85
Red	Below 0.70

Info-only checks

These show up when you click the icon but never change its colour — they're about your logging, not your engine.

Check	Condition
Dead channel	A channel a healthy car varies continuously — rpm, coolant / oil / intake temperature, oil / fuel pressure, battery voltage, fuel level, speed, throttle, brake, steering, lateral G — is flat for the whole session. Usually an unplugged sensor or a channel that isn't wired.
Wheel vs GPS speed	The median ratio of wheel speed to GPS speed, above 10 m/s, falls outside 0.9–1.1 — a tyre-size or scaling mismatch in the logger's setup.

See it on your own sessions

Upload a session with engine channels — from your logger, or merged in from your ECU — and the icon appears in your session list.

Get started — free