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.
1991 Acura Legend Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Automatic Transmission Shift Position Signal
- While watching shift indicator, shift transmission gear to each position. If shift indicator lights up correctly for all positions, turn ignition off. Connect PGM-FI test harness between ECU and ECU connectors. Disconnect connector "B" from main harness only; DO NOT disconnect from ECU. Turn ignition on. Measure voltage between ECU terminals B7 (positive) and A26 (negative). If voltage is not around 10 volts, substitute a known good ECU, and recheck voltage.
- If voltage is about 10 volts, reconnect connector "B" to main wiring harness. Place transmission in Neutral. Measure voltage between terminals B7 (positive) and A26 (negative). If voltage is more than 1 volt, repair open in Light Green wire between ECU B7 and connector.
- If voltage is less than 1 volt, place transmission in Park, and measure voltage between terminals B7 (positive) and A26 (negative). If voltage is more than one volt, replace shift position signal.
- If voltage is not more than one volt, place transmission in Drive, and measure voltage between terminals B7 (positive) and A26 (negative). If voltage is not about 10 volts, repair short in Light Green wire between ECU terminal B7 and combination meter. If voltage is about 10 volts, shift position signal is okay.
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.
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