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.

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HOMESERVICE MANUALSTOYOTA2004CELICA GT, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 345 (ENGINE CONTROL SYSTEM - DIAGNOSIS)CHECK MODE PROCEDURE

2004 Toyota Celica GT, Standard

Check Mode Procedure

2004 Toyota Celica GT, StandardSECTION Check Mode Procedure

WARNING: This page is about a different car, the 2004 Lexus ES 330. However, it is still accessible from the selected car via links, so may be relevant.

HINT: Hand-held tester only:

Check mode has a higher sensitivity to detect malfunctions and can detect malfunctions that normal mode cannot detect.

Check mode can also detect all the malfunctions that normal mode can detect.

CHECK MODE PROCEDURE (Using the hand-held tester)
1. Make sure that the items below are true.
  1. Battery positive voltage 11 V or more
  2. Throttle valve fully closed
  3. Transmission in the P or N position
  4. A/C switched OFF
2. Turn the ignition switch to OFF.
3. Connect the hand-held tester to the DLC3.
4. Turn the ignition switch to ON.
5. Change the ECM to check mode with the hand-held tester. Make sure the MIL flashes as shown in the illustration.
  
  Fig 1: Connecting Hand-Held Tester To DLC3
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

RENDER: 1.0x

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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.