Sensors¶
The ECU's inputs at a glance, and how each one feeds the fuel and spark decisions.
What the ECU reads¶
The ECU can't see the engine directly — it infers everything from a handful of sensors. Each one feeds specific decisions:
| Sensor | Measures | Feeds |
|---|---|---|
| MAP | Manifold pressure (load) | Speed-density, table lookups, AE trigger |
| TPS | Throttle position / demand | Idle control, AE, DFCO |
| CLT/ECT | Coolant temperature | Enrichment, cold idle, knock, timing |
| IAT | Intake air temperature | Charge density, knock |
| O2 / Lambda | Exhaust mixture | Closed-loop trim |
| Fuel Pressure | Rail pressure | Injector flow correction, closed-loop gating |
| Barometric | Atmospheric pressure | Load ratios, altitude scaling |
Why it matters¶
Tuning is only as good as the signals it's based on. Understanding what each sensor measures — and which decision depends on it — is how you diagnose a problem: a lean condition might be a fuel-pressure issue, a rich warm idle might be a coolant-temperature reading, a flat spot might be the MAP signal driving acceleration enrichment.