Your diagnostic mission
The starter turns the engine at normal cranking speed, but the engine does not run. Your job is to distinguish engine-position reference, fuel supply, ignition power, and mechanical timing faults. Every customer complaint sounds similar—your test results will not.
1 · Choose a service ticket
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2 · Think before testing
Normal cranking is established. Select a test that separates competing hypotheses; then compare your results with the ECM’s reported data.
A hypothesis is a starting point—not a diagnosis.
Evidence checklist
3 · Select diagnostic tests
Each test returns the result for the selected service ticket. Results are retained in your evidence log.
4 · Your evidence log
- Choose a test to reveal the first piece of evidence.
5 · Defend your diagnosis
Make a fault selection and cite at least two independent observations. You can try early; the Challenger will tell you what important evidence is still missing.
6 · Diagnostic thinking
| Observation | What it establishes |
|---|---|
| Scan-tool RPM = 0 while cranking | Investigate engine-speed data and CKP circuit; confirm a physical reference signal before condemning the sensor. |
| Fuel pressure is low | Investigate delivery; test pump power/ground and capacity before replacing a pump. |
| No spark at multiple cylinders | Check shared power, timing reference, and command—not just individual coils. |
| Cam/crank correlation is abnormal | Compare sensor signals and mechanical timing; a correlation code alone does not prove a chain or belt fault. |
A complete diagnosis connects symptom → test → observation → ruled-out alternative → next action.
Learning check: no-start diagnostic categories
Which statement is supported by a normal cranking speed?