What does it mean?
P1148 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Generator 2 Control Circuit Malfunction .
Symptoms
- Malfunction indicator lamp or the charge warning lamp illuminated
- System voltage lower or higher than normal on the instrument display
- Headlights and interior lighting dimming or brightening with engine speed
- Battery going flat overnight or after a short standing period
- Auxiliary equipment powered by the second generator working poorly or not at all
Likely causes
- Open, shorted or chafed control wire between the module and the second generator
- Corroded or loose connector at the generator regulator
- Failed internal voltage regulator inside the second generator
- Slipping, glazed or broken drive belt for that generator
- Blown fuse or fusible link in the generator's field or sense circuit
- Poor generator ground or a corroded main output cable connection
- Faulty control output inside the PCM or the body control module driving the circuit
How to fix it
- Measure battery voltage with the engine off, at idle and at raised engine speed, then compare with the specified charging range
- Read live data for the generator command and the reported output to see whether the module and unit agree
- Inspect the drive belt tension and condition, and confirm the pulley is not slipping
- Check the control circuit for continuity from the module connector to the generator plug and test for shorts
- Clean and retighten the generator output cable, ground strap and battery terminals
- Check the fuse and fusible link in the charging circuit before condemning the unit
- Replace the second generator or its regulator once wiring, belt and grounds prove good, then verify charging under load