1999 Chevy Camaro OBD2 diagnostics

Tiny
ROB LUDLOW 44
  • MEMBER
  • 1999 CHEVROLET CAMARO
  • V8
  • 2WD
  • MANUAL
  • 238,000 MILES
Hand held code reader will not read. Message says connect cables, they are connected!

Further checking shows no +12v at pin #16, ground on pin 4 OK.

So diagnostics codes can not be received. There is +12v at ECM on the orange wires as required and all fuses are good.

Can't find nor trace where the +12v at pin #16 on the ALDL connector comes from.

Is this an ECM problem? Or where do you start to trace this? It does not show up any schematics, as to where the pin 16 ALDL orange wire is connected to a source. LOST without diagnostics! Any clues?

THANKS,
Rob
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Tuesday, March 17th, 2009 AT 12:54 PM

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Tiny
MERLIN2021
  • EXPERT
4.3L, 5.0L, 5.7L (VIN R) & 7.4L 1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. After performing OBD system check, go to next step. 2. Connect scan tool to a known-good vehicle. If scan tool displays VCM data, go to step 4. If scan tool does not display VCM data, go to next step. 3. Repair scan tool or scan tool cables. 4. Reconnect scan tool to original vehicle. If scan tool powers up, go to next step. If scan tool does not power up, go to step 9. 5. Using scan tool, select correct vehicle application. If vehicle information is correct, go to next step. If vehicle information is not correct, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. 6. Turn ignition on. Using scan tool, monitor class 2 serial data. If any modules on serial data circuit are communicating, go to step 13. If no modules communicate, go to next step. 7. Turn ignition off. Disconnect components sharing serial data circuit, leaving VCM connected. Turn ignition on, with engine off. If scan tool displays VCM data, diagnose class 2 serial data circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If scan tool does not display VCM data, go to next step. 8. Turn ignition off. Disconnect VCM harness connector C4. See appropriate wiring diagram in WIRING DIAGRAMS article. Using a test light connected to battery positive, probe class 2 serial data circuit at DLC (terminal No. 2). If test light illuminates, go to step 20. If test light does not illuminate, go to step 13. 9. Using a test light connected to ground, probe battery positive feed circuit at DLC (terminal No. 16). See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12. 10. Using a test light connected to battery positive, probe ground circuit at DLC (terminal No. 4). See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 16. 11. Using a test light connected to battery positive, probe ground circuit at DLC (terminal No. 5). See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step 18. If test light does not illuminate, go to step 16. 12. Inspect fuse associated with battery feed circuit. If fuse is open, go to step 14. If fuse is okay, go to step 15. 13. Check for open or poor connection in class 2 serial data circuit. If a problem is found, go to step 17. If circuit is okay, go to step 19. 14. Check for short to ground in battery feed circuit. Repair as necessary and replace fuse. After repairs, go to step 23. 15. Repair open in battery feed circuit. After repairs, go to step 23. 16. Repair open in DLC ground circuit. After repairs, go to step 23. 17. Repair open or poor connection in class 2 serial data circuit. After repairs, go to step 23. 18. Check for poor connections at DLC. If a problem is found, go to step 21. If connections are okay, see appropriate TROUBLE SHOOTING - NO CODES article. NOTE: Perform On-Board Diagnostic (OBD) system check after completing any repairs. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. Page 1 of 2 TESTS W/CODES - INTRODUCTION -1999 Chevrolet Camaro19. Check class 2 serial data circuit for poor connections at VCM and DLC. If a problem is found, go to step 21. If circuit connections are okay, go to step 22. 20. Repair short to ground in class 2 serial data circuit. After repairs, go to step 23. 21. Repair circuit as necessary. After repairs, go to step 23. 22. Replace VCM. Perform VCM, Passlock(R) and CKP system relearn procedures. After repairs, go to next step. 23. Using scan tool, check for DTCs. If any additional DTCs are present, diagnose DTCs. See DIAGNOSTIC TESTS in appropriate TESTS W/CODES article. If no DTCs are present, system is okay.
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Tuesday, March 17th, 2009 AT 1:58 PM

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