2001 Honda Prelude Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Neutral Position Switch Signal Circuit (Insight)

NOTE: This signal informs PCM when transaxle is shifted out of neutral.
  1. Turn ignition on. Shift transaxle into 1st gear. Backprobing, measure voltage between PCM connector "B" (25-pin connector) terminals No. 16 (Red/Black wire) and No. 20 (Brown/Black wire). See Figure. If battery voltage exists, go to next step. If battery voltage does not exist, go to step  3.
  2. Shift transaxle into Neutral. Backprobing, measure voltage between PCM connector "B" (25-pin connector) terminals No. 16 (Red/Black wire) and No. 20 (Brown/Black wire). See Figure. If voltage is not less than one volt, go to step  5. If voltage is less than one volt, problem is intermittent. Neutral position switch signal is okay at this time.
  3. Turn ignition off. Disconnect neutral position switch 2-pin connector. Turn ignition on. Backprobing, measure voltage between PCM connector "B" (25-pin connector) terminals No. 16 (Red/Black wire) and No. 20 (Brown/Black wire). See Figure. If battery voltage is not present, go to next step. If battery voltage is present, replace neutral position switch.
  4. Turn ignition off. Disconnect PCM connector "B" (25-pin connector). Check continuity of Red/Black wire between body ground and PCM connector "B" (25-pin connector) terminal No. 16. See Figure. If continuity is present, repair short in Red/Black wire between neutral position switch and PCM connectors. See WIRING DIAGRAMS article. If continuity is not present, substitute a known-good PCM and retest. See SUBSTITUTING POWERTRAIN CONTROL MODULE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INSIGHT article. If symptom or indication goes away, replace original PCM.
  5. Turn ignition off. Disconnect neutral position switch 2-pin connector. With transaxle in 1st gear, measure continuity across both terminals of neutral position switch. If continuity is present, go to next step. If continuity is not present, replace neutral position switch.
  6. Turn ignition on. With transaxle in 1st gear, measure voltage of Red/Black wire between body ground and neutral position switch 2-pin connector terminal No. 2. If battery voltage exists, repair short in Black wire between neutral position switch and ground point located on top of engine, near MAP sensor. If battery voltage does not exist, repair open in Red/Black wire between neutral position switch and PCM connectors. 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.

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