Exterior lighting and strange voltages
Lamp is off but your meter still shows 7 V. Is something feeding it when it shouldn’t?
What this lesson covers
CORE TEACHING BCM outputs; PWM; bulb monitoring; cold/warm diagnostics; LEDs/drivers; high-side/low-side control. Add LED headlamp driver modules, constant-current control, bulb-out monitoring, diagnostic pulses and why modern LED units may have permanent feeds plus network/control inputs. PRACTICAL DEMONSTRATIONS AND TESTS Meter output off/on; test lamp/load; scope PWM; compare incandescent vs LED circuit. ADVANCED / SCAN TOOL LAYER Oscilloscope is a major teaching layer: PWM duty cycle, diagnostic pulses, switched ground. KEY DIAGNOSTIC QUESTIONS Is this continuous power, PWM, or diagnostic pulsing? Can it drive the intended load? MUST-COVER CHECKPOINTS Map simple vs module-controlled architecture; prove heavy power and ground; verify switch/request; command output; measure load current; inspect signal/network where used.
What you will be able to do
Lamp is off but your meter still shows 7 V. Is something feeding it when it shouldn’t?
Where it sits in the programme
- Builds on
- Lesson 29: Central locking and keyless handles
- Feeds into
- Lesson 31: Blower motor diagnosis