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 MANUALSTOYOTA2004MATRIX XR, FWD, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 16 (ENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - V6)DIAGNOSTIC TESTSDTC P1520: STOPLIGHT SWITCH SIGNAL CIRCUITDIAGNOSIS & REPAIR
2004 Toyota Matrix XR, FWD, Standard
Diagnosis & Repair
2004 Toyota Matrix XR, FWD, StandardSECTION Diagnosis & Repair
WARNING: This page is about a different car, the 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
- Check stoplight operation. If stoplights operate properly, go to next step. If stoplights do not operate properly, repair as necessary and retest system. See EXTERIOR LIGHTS article in ACCESSORIES & EQUIPMENT.
- Access ECM behind glove box. See Figure. Turn ignition on. Using DVOM, backprobe ECM harness connector and measure voltage between ground and terminal No. 15 (Green/White wire) at ECM harness connector E5. See Figure. Voltage should be 7.5-14.0 volts with brake pedal depressed, and less than 1.5 volts with brake pedal released. If voltage is not as specified, go to next step. If voltage is as specified, problem is intermittent. Check component and ECM connections.
- Check for open or short in wiring between ECM and stoplight switch. If problem exists, repair wiring as necessary. If problem does not exist, replace ECM.
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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.