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 MANUALSACURA19983.5RL SPECIAL EDITIONREPAIR AND DIAGNOSISTRANSMISSIONAUTOMATIC TRANSDIAGNOSIS - M5DADTC/FLASH CODE TESTSDTC P1791/FLASH CODE 4: VEHICLE SPEED SENSOR (VSS)
1998 Acura 3.5RL Special Edition
DTC P1791/Flash Code 4: Vehicle Speed Sensor (VSS)
1998 Acura 3.5RL Special EditionSECTION DTC P1791/Flash Code 4: Vehicle Speed Sensor (VSS)
- Ensure speedometer operates correctly. If speedometer does not operate correctly, diagnose VSS. See VEHICLE SPEED SENSOR (VSS) under COMPONENT TESTING. If speedometer operates correctly, go to next step.
- Turn ignition off. Raise and support front of vehicle. Shift transaxle to Neutral. Disconnect PCM harness connectors "A" (26-pin) and "B" (16-pin). See Figure . Turn ignition on. Connect DVOM to PCM harness connector "A" terminal No. 26 (Brown/Black wire) and connector "B" terminal No. 13 (Blue/White wire). Block the opposite front wheel while rotating the other wheel. If voltage reading is zero and about 5 volts or greater and alternating, go to next step. If voltage reading is not zero and about 5 volts or greater and alternating, go to step 4 .
- Check for loose PCM connectors. Repair as necessary. If connectors are okay, substitute with a known-good PCM and recheck system. If symptom or problem goes away, replace original PCM.
- Check for open in circuit between PCM harness connector "B" terminal No. 13 (Blue/White wire) and VSS. Repair as necessary. See WIRING DIAGRAMS . If circuit is okay, diagnose VSS. See VEHICLE SPEED SENSOR (VSS) in COMPONENT TESTING.
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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.