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Home >> Cadillac >> 1989 >> Allante F7/ME9 >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Body Computer Module >> Diagnostic Tests >> DTC L203: OSM No. 3 Communication Problem >> Test Procedure

Test Procedure

  1. If you were not directed here from Lighting chart A-1, then a wrong diagnosis could result. See 1989 SELF-DIAGNOSTICS -- ALLANTE article in ENGINE PERFORMANCE.
  2. Visually inspect the cavities and pins of the OSM for obvious connection problems.
  3. Make sure that there is indeed power to the OSM.
  4. Checks for proper ground to the OSM.
  5. Checks for proper OSM address identification.
  6. 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.
Fig 1: DTC L203: OSM No. 3 Communications Problem Flow Chart
G00103607Courtesy of GENERAL MOTORS CORP.
Fig 2: DTC L203: OSM No. 3 Communications Problem Flow Chart Circuit
G00103608Courtesy of GENERAL MOTORS CORP.
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