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 P0720/FLASH CODE 9: COUNTERSHAFT SPEED SENSOR
1998 Acura 3.5RL Special Edition
DTC P0720/Flash Code 9: Countershaft Speed Sensor
1998 Acura 3.5RL Special EditionSECTION DTC P0720/Flash Code 9: Countershaft Speed Sensor
- Ensure countershaft speed sensor is properly installed. Reinstall sensor and recheck operation. If sensor is properly installed, go to next step.
- Turn ignition off. Disconnect countershaft speed sensor harness connector. Check resistance between sensor terminals. If resistance is 400-600 ohms, go to next step. If resistance is not 400-600 ohms, replace countershaft speed sensor.
- Disconnect 26-pin PCM harness connector "E". Check continuity between chassis ground and PCM harness connector "E" terminals No. 5 (Blue wire), then No. 18 (Green wire). See Figure . If continuity does not exist, go to next step. If continuity exists, repair short in circuit between PCM harness connector "E" terminals No. 5 and No. 18, and countershaft speed sensor. See WIRING DIAGRAMS .
- Reconnect countershaft speed sensor harness connector. Check resistance between PCM harness connector terminals No. 5 (Blue wire) and No. 18 (Green wire). If resistance is 400-600 ohms, go to next step. If resistance is not 400-600 ohms, repair loose terminal or open in circuit between PCM harness connector terminals No. 5 and No. 18 and countershaft speed sensor.
- Check for loose PCM harness 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.
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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.