Applies to: 2001-’04 Honda Civic
Got a 2001-’04 Civic in your shop with any or all of these symptoms?
The engine cranks but it won’t start.
The MIL comes on.
The immobilizer indicator blinks while the engine cranks.
The HDS can’t communicate with the ECM/PCM.
Check for loose alternator bolts. If these bolts are loose for any reason such as the alternator was R&R’ed, or an accessory A/C was installed on a DX model at the dealership, the alternator can overcharge and fry the ECM/PCM.
If the alternator bolts are loose, tighten them and try restarting the engine. If the engine still won’t start, then check the ECM/PCM connector for battery voltage and ground. If you’re reading battery voltage and ground at the connector, then replace the ECM/PCM. Keep in mind, though, any ECM/PCM damage that’s caused by loose alternator bolts from A/C installation or body repair isn’t covered under warranty.
Courtesy of Honda Service News via ALLDATA.