DTC L203: OSM No. 3 Communication Problem: Description
Code L203 indicates that the BCM has been unable to correctly communicate information to OSM No. 3. This fault could affect the operation of the left stop/turnlamps "C" and "D" and the left taillamps "C" and "D".
NOTE:
The following numbered steps refer to circled numbers on diagnostic chart. See Fig 1. For circuit identification, see Fig 2.
- If you were not directed here from Lighting Chart A-1, a wrong diagnosis could result if not performed first. See LIGHTING CHART A-1 in SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
- Visually inspect the cavities and pins of the OSM for obvious connection problems.
- Make sure that there is indeed power to the OSM.
- Checks for proper ground to the OSM.
- Checks for, proper OSM address identification.
- Hazard flashers will increase data line activity. Typical voltages will be between zero and 5 volts and will constantly be changing. This will help identify whether the OSM or the data line is the problem.
NOTE:
When all diagnosis and repairs are completed, clear codes and verify operation.