2003 Cadillac CTS StandardFACTORY OEM SERVICE PROCEDURE

Diagnostic Procedures

  1. If I/M system check has been performed, go to next step. If I/M system check has not been performed, go to INSPECTION/MAINTENANCE SYSTEM CHECK .
  2. Ensure that the vehicle is within the Conditions for Running. Turn OFF all of the accessories (e.g., A/C, blower fan, etc.). Set the vehicle parking brake. Verify the transmission is in Park for A/T and Neutral for M/T. Start engine. Allow engine to idle for 2 minutes. When complete, go to next step.
    3. WARNING: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
  3. Test drive vehicle. Ensure vehicle is accelerated at part throttle to 55 MPH. Drive vehicle at 55 MPH for 16 minutes. Decelerate vehicle to zero MPH. Idle engine for 40 seconds while service brake is depressed and automatic transmission is in Drive or manual transmission is in Neutral with clutch pedal depressed. Repeat procedure 4 times.
  4. Ensure vehicle is accelerated at part throttle to 45-55 MPH. Drive vehicle at 45-55 MPH for 8 minutes. Decelerate vehicle to zero MPH. Idle engine for 40 seconds while service brake is depressed and automatic transmission is in Drive or manual transmission is in Neutral with clutch pedal depressed. Repeat procedure 4 times.
  5. Using scan tool, observe I/M system status display. If all I/M system status indicators updated to YES, go to next step. If any I/M system status indicator did not update to YES, repeat I/M System Set Procedure for indicated system.
  6. Using scan tool, observe emission related DTC portion of I/M system status display. If scan tool indicates any emission related DTCs, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not indicate emission related DTCs, system is okay.
Chapter Navigation
Return to Chapter: Inspection/Maintenance Complete System Set Procedure
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.