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 15 (ENGINE CONTROL SYSTEM SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P1127: ELECTRONIC THROTTLE CONTROL SYSTEM ACTUATOR POWER SOURCE CIRCUITDIAGNOSIS & REPAIR
2004 Toyota Celica GT, Standard
Diagnosis & Repair
2004 Toyota Celica GT, StandardSECTION Diagnosis & Repair
WARNING: This page is about a different car, the 2002 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
- Remove THRO fuse (15-amp) from fuse/relay box at driver's side front corner of engine compartment. See Fig 1. Check THRO fuse. If THRO fuse is okay, reinstall THRO fuse and go to next step. If THRO fuse is defective, replace fuse and check for short in Gray wire between THRO fuse and ECM. See WIRING DIAGRAMS article. ECM is located behind glove box. See Figure. Repair wiring as necessary.
- Remove glove box for access to ECM with electrical connectors still installed on ECM. See Figure. Using voltmeter, check voltage between body ground and terminal No. 6 (Gray wire) at ECM electrical connector E7. See Figure. This is the +BM terminal on ECM. Voltage should 9-14 volts. If voltage is within specification, replace ECM. If voltage is not within specification, repair open or short in wiring harness and electrical connectors between battery, THRO fuse and +BM terminal on ECM. See WIRING DIAGRAMS article.
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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.