- Added symptom reference guide (what to see/not see with key ON)
- 7-step diagnostic test plan:
1. Basic power check (dash lights, fuel pump prime)
2. ECM fuse voltage test (both sides - corroded contacts)
3. ECU relay swap test
4. Fuse box inspection (water damage/corrosion)
5. ECU power pin test (verify 12V at connector)
6. ECU ground pin test (<1 ohm)
7. Fusible link test (continuity + voltage)
- Test decision tree for troubleshooting flow
- Priority order (immediate tests first)
- Documentation template for recording results
- Based on similar GM Express/Savana cases found online
- Answers John's questions: dash lights, check engine light, multiple ECU power points
- Documented John's insight: Two ECUs failing identically suggests power supply issue
- Researched GM Express no-spark cases online
- Found similar cases: corroded fuse box, water intrusion, bad fusible links
- Key finding: Cleaning corroded fuse boxes has restored function in similar cases
- Water damage patterns: fuse box corrosion, ECU connector corrosion, ground points
- Why two ECUs fail same way: power supply issue affects both identically
- Diagnostic priorities: Check ECM fuses, inspect fuse box, clean contacts
- Resources: fuse-box.info, 2CarPros, GM forums, JustAnswer cases
- If power is fixed, eBay ECU should work - save 00-500!
- John correctly noted: Two ECUs failing identically is suspicious
- New theory: ECU power supply issue (fuse/relay/fusible link) could cause both ECUs to fail
- Water damage from puddle incident may have corroded fuse box or power distribution
- If ECU power is bad, eBay ECU won't work either
- This could save 00-500 on replacement ECU
- Added detailed ECU power supply diagnostic procedure:
- Check ECU fuses (ECM, IGN, EFI, FUEL PUMP)
- Check ECU relay (swap with horn relay)
- Test ECU power pins (should be 12V clean)
- Test ECU ground pins (should be 0V)
- Check fusible links
- Inspect fuse box for water damage
- NEW PRIORITY: Fix power supply BEFORE replacing ECU again
- John used T-pin to ground ECU trigger wire at ICM connector
- Engine fires and runs when trigger wire grounded
- PROVES: Everything after ECU works perfectly
- CONCLUSIONS:
- CKP sensor: WORKS (produces ~5V square wave)
- CMP sensor: WORKS (has power/ground)
- ICM: WORKS (responds to ground trigger)
- Ignition coil: WORKS (fires when triggered)
- Spark plugs/wires: WORKS (engine fires)
- ROOT CAUSE: ECU not sending trigger signal
- The eBay replacement ECU is also bad (internal water damage)
- NEXT: Replace ECU with known-good unit
- CKP square wave test: ~5V signal when flywheel turned manually
- CKP sensor IS producing signal - rules out CKP failure
- Detailed wiring analysis from John's notes:
- Distributor plug: 12V power, good ground
- Ignition coil: Resistance measurements show coil intact
- ICM back plug: 12V power present, ground present
- Problem: No trigger from ECU to ICM (0V vs 6.3V good)
- CONCLUSION: ECU internal damage from water intrusion
- The eBay replacement ECU is also bad
- Next: Replace ECU with known-good unit
- Added CKP sensor voltage readings: 10.9V power (good) vs 11.38V reference
- Added CMP sensor voltage readings: 12V power, ground, signal all good
- Added ICM voltage readings showing 0V trigger signal in bad van
- CRITICAL FINDING: ECU not sending trigger to ICM (0V vs 6.3V in good van)
- CKP power supply verified GOOD - not the problem
- CKP AC signal test while cranking still needed
- Root cause: ECU not firing coils despite good CKP power
- Create CrankNoStart/ folder with README.md and progress.md
- Set up issue tracking template for no-spark condition
- Document diagnostic priority order and common failure points
- Add tools, parts, and resources sections
- Update main README with active issue status (High urgency)
- README.md with vehicle info template and typical specs
- ISSUE_TEMPLATE.md for tracking maintenance issues
- Project ready for John to add VIN and start documenting issues
John Loper II