Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2003 Cadillac CTS StandardFACTORY OEM SERVICE PROCEDURE
Diagnostic Procedures
- 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 .
- Ensure the vehicle is within the Conditions for Running. Turn OFF all of the accessories (e.g., A/C, blower fan, etc.). Start and idle the engine. In order for this test to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 55 MPH. Maintain this speed for 8 minutes. Decelerate 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. Using scan tool, observe the I/M system Status display. Did the Catalyst System Status update to YES? If yes, go to step 5. If no, go to next step.
- Using scan tool, observe DTC Information. Does the scan tool indicate any failed DTCs? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
- Refer to the Inspection/Maintenance (I/M) System DTC Table To determine which DTCs are required to run in order to complete this test. See INSPECTION/MAINTENANCE SYSTEM DTCS . Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Enter DTC in Specific DTC menu on scan tool. Operate vehicle within Conditions for Running DTC. Repeat procedure until scan tool indicates the diagnostic test has run. Repeat this step for any additional required DTCs that have not run. Using scan tool, observe I/M System Status display. Did the Catalyst System Status update to YES? If yes, go next step. If no, see DIAGNOSTIC AIDS .
- Using scan tool, observe emission related DTC portion of I/M System Status display. Does scan tool indicate any emission related DTCs? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
WARNING:
Road test 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.
Factory Service Tools
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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.