Lambda / oxygen sensors and fuel-control feedback
A petrol engine runs rich and logs mixture faults. Is the oxygen sensor reporting the problem, causing the problem, or simply reacting correctly?
What this lesson covers
CORE TEACHING Narrowband O2 vs wideband/air-fuel ratio sensor; heater circuits; upstream vs downstream roles; closed-loop control; stoichiometric concept; fuel trims; sensor response; exhaust leaks; catalyst monitoring; why wideband current/scan values differ from old 0–1 V narrowband thinking. PRACTICAL DEMONSTRATIONS AND TESTS Graph upstream/downstream signals; test heater power/ground/current; create a controlled rich/lean change where safe; compare short/long-term fuel trim; scope narrowband switching or view wideband current/PID. ADVANCED / SCAN TOOL LAYER Scope narrowband waveform; scan wideband equivalence ratio/current; fuel-trim graphs; catalyst comparison. KEY DIAGNOSTIC QUESTIONS Does the signal make sense with the actual mixture? Is the heater working? Does the sensor respond when mixture changes? Are exhaust leaks fooling it? MUST-COVER CHECKPOINTS Identify sensor type and position; heater; response/plausibility; rich/lean influence; fuel trims; upstream/downstream comparison; sensor-vs-engine verdict.
What you will be able to do
A petrol engine runs rich and logs mixture faults. Is the oxygen sensor reporting the problem, causing the problem, or simply reacting correctly?
Where it sits in the programme
- Builds on
- Lesson 40: Automotive Ethernet & DoIP — modern ADAS and gateway networks
- Feeds into
- Lesson 42: EGR systems — electrical command vs actual gas flow