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 MANUALSHONDA1998CIVIC DX, 2D COUPE, AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - SYSTEM & COMPONENT TESTINGIDLE CONTROL SYSTEMALTERNATOR FR SIGNAL
1998 Honda Civic DX, 2D Coupe, Automatic
Alternator Fr Signal
1998 Honda Civic DX, 2D Coupe, AutomaticSECTION Alternator Fr Signal
NOTE:
This signal informs PCM when alternator is charging.
- Turn ignition off. Disconnect alternator 4-pin connector (3-pin on Canadian models). Turn ignition on. Measure voltage between PCM connector terminals B20 and C5 (Accord, CR-V, Oasis & Odyssey) or terminals A9 and C17 (Civic & Prelude). See Figure . If about 5 volts exists, go to step 3). If about 5 volts does not exist, go to next step.
- Turn ignition off and disconnect negative battery cable. Disconnect PCM connector "C" on all models. Check for continuity between ground and PCM connector terminal C5 (Accord, CR-V, Oasis & Odyssey) or terminal C17 (Civic & Prelude). If continuity exists, repair short in wire between PCM connector and alternator connector. If continuity does not exist, substitute known-good PCM and recheck for about 5 volts. If about 5 volts now exists, replace original PCM.
- Turn ignition off and reconnect alternator connector. Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral, until radiator fan comes on. Allow engine to idle. Measure voltage between PCM connector terminals B20 and C5 (Accord, CR-V, Oasis & Odyssey) or terminals A9 and C17 (Civic & Prelude). If voltage does not decrease when headlights and rear defogger is turned on, go to next step. If voltage decreases when headlights and rear defogger is turned on, alternator FR signal is okay.
- Turn ignition off. Disconnect negative battery cable. Disconnect PCM connector "C" on all models. See Figure . Disconnect alternator 4-pin (3-pin on Canadian models) connector. On all models, connect a jumper wire between ground and alternator harness connector No. 4 terminal. See Fig 1 . Check for continuity between ground and PCM connector terminal C5 (Accord, CR-V, Oasis & Odyssey) or C17 (Civic & Prelude). If continuity exists, problem is within alternator or regulator. If continuity does not exist, repair open in wire between PCM connector and alternator harness connector.
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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.