Temperature sensors in real diagnosis

CORE TEACHING Coolant/IAT/oil temp use; plausibility; cross-sensor comparison after overnight soak; wiring faults. PRACTICAL DEMONSTRATIONS AND TESTS Cold-soak compare ECT/IAT/ambient; warm engine and graph rise; resistance/voltage checks. ADVANCED / SCAN TOOL LAYER Graph PIDs; scope intermittent wiring if tapping harness reproduces spikes. KEY DIAGNOSTIC QUESTIONS What should temperature physically be right now? Which sensors should agree? MUST-COVER CHECKPOINTS Identify sensor technology; supply/ground if applicable; expected signal type; physical stimulus; scan comparison; scope if time-varying; wiring-to-ECU proof.

Cold engine shows 86°C before it has even started.

Builds on

Lesson 23: Pressure sensors — MAP, rail and A/C

Feeds into

Lesson 25: Position sensors and plausibility

1. 18Power, ground and signal — the universal sensor pattern
2. 19Testing a three-wire sensor
3. 20Two-wire temperature and resistive sensors
4. 21Hall-effect cam and crank sensors
5. 22Inductive sensors and AC signals
6. 23Pressure sensors — MAP, rail and A/C
7. 24Temperature sensors in real diagnosis
8. 25Position sensors and plausibility
9. 26Testing actuators: motors, solenoids and valves