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.
Alternator Fr Signal: MDX
2004 Acura 3.5RLSECTION MDX
- Start engine and allow to idle. With the Honda PGM-FI Tester or the HDS monitor the ALTERNATOR in the DATA LIST. If the indicated percentage is varied when the lighting switch is turned on, the alternator signal circuit is OK. If the indicated percentage is not varied when the lighting switch is turned on, go to next step.
- Turn lighting switch and ignition off. Disconnect alternator 4-pin connector. Turn ignition on. Measure voltage between ground and alternator 4-pin connector terminal No. 4 (White/Red wire). If about 5 volts is present, replace alternator, then go to step 1 . If about 5 volts is not present, go to next step.
- Turn ignition off. Disconnect PCM harness connector "A". See Figure . Check for continuity between ground and alternator 4-pin connector terminal No. 4 (White/Red wire). If there is continuity, repair short in wire between alternator 4-pin connector terminal No. 4 (White/Red wire) and PCM. If there is no continuity, go to next step.
- Check for continuity between PCM harness connector terminal A25 and alternator 4-pin connector terminal No. 4 (White/Red wire). If there is continuity, update the PCM if it does not have the latest software. Substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM. If there is no continuity, repair open in wire between alternator 4-pin connector terminal No. 4 (White/Red wire) and PCM.
RENDER: 1.0x
NO RELATED
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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.