Finding open circuits
Signal disappears somewhere between sensor and ECU. Where exactly is the broken wire?
What this lesson covers
CORE TEACHING Open circuit; continuity limitations; divide-and-conquer/sectioning; connector points; pull-ups/backfeeds. PRACTICAL DEMONSTRATIONS AND TESTS Check voltage at source/end; continuity de-energised; split loom at intermediate connector; wiggle test. ADVANCED / SCAN TOOL LAYER Scope can catch intermittent opens; scan shows PID dropouts. KEY DIAGNOSTIC QUESTIONS Where does the signal exist last? Where does it disappear first? MUST-COVER CHECKPOINTS Define fault electrically; isolate circuit; choose powered/unpowered method correctly; divide circuit; load-test repair; wiggle/verify; protect wiring during test.
What you will be able to do
Signal disappears somewhere between sensor and ECU. Where exactly is the broken wire?
Where it sits in the programme
- Builds on
- Lesson 49: Loaded circuit testing
- Feeds into
- Lesson 51: Finding shorts to ground
More in Diagnostic Method
- 47Power–ground–signal: the default framework
- 48Test the connector before replacing the component
- 49Loaded circuit testing
- 50Finding open circuits
- 51Finding shorts to ground
- 52Finding shorts to positive and back-feeds
- 53Parasitic battery drains
- 54When pulling one fuse kills the drain
- 55ECUs and control modules
- 56The complete Voltzs diagnostic workflow