So I got a car from a friend that owed me some money. The car runs fine but for some reason the alternator will not come on. (Replaced the alternator battery and fuse box.) He claims the car was running fine but they cut the exaust off after the cat for a week while they were waiting for the new one to come in. It had a hole in it farther down. Well the o2 sensor got ripped in half and the car started bogging down after about a week.They got it home replaced the o2 sensor amd put the new exhaust on. But now the car will just not charge. It's a 04 Honda accord lx k24a1. I don't know what else to look for any help would be greatly appreciated.

(I'm thinking the ECU is probably shot since it's also in limp mode or should I just get the codes all reset)

 

The PCM can shut down the alternator, when the battery voltage is good and the electrical loads are low. It does this by grounding a control wire to the alternator. So if the insulation is rubbed off that wire somewhere, and shorting to ground, that causes the alternator to shut down just as if the PCM had commanded it to shut down.

So... look for a short to ground in one of the alternator wires. I don't have a wiring diagram for 2004, so maybe someone with that will chime in.

 

1. At the connector to the alternator, with the ignition switch in the ON or START position, check to see if there is power (+) at the Blk/Yel (IG) wire. Under-dash Fuse No. 18 (15A) supplies the ignition input that turns on the alternator/regulator assembly. If that fuse is blown or there is no power going through the Blk/Yel wire to the alternator when the ignition switch is turned ON, the alternator will not charge.

2. On a side note: Honda's utilizes a dual mode charging system to increase fuel efficiency and reduce drag on the engine on start-up. The ECM/PCM determines charging based on info. from the ELD. During heavy load, the ECM/PCM can set charging voltage for high output (~14V - 15V). During light load and start-up, the ECM/PCM sets charging voltage for low output (~12 - 13V).

Most previous generation Hondas had alternator/voltage regulators which utilize five terminal wires: Ignition (IG), Control (C), Field Reference (FR), Battery (B), and Lamp (L). The wires between the alternator's voltage regulator and PCM are the C, FR, and L wires. The ECM/PCM can control charge modes (high or low output).

The ECM/PCM will not shut off the alternator.

 

OK, sorry. Did that newer system start in 2003 with the 7th-gen?

 

Holy **** it worked thank you so much