What does it mean?
P1412 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Exhaust Gas Recirculation (EGR) Cooler Bypass Valve Control Circuit 2 High Voltage .
Symptoms
- MIL on, usually together with other EGR or emission related codes
- EGR gas is no longer routed through the cooler, so exhaust temperature and NOx output rise
- Possible emissions test failure
- Mild loss of drivability and slightly rough running at light load
- The valve does not click or move during a scan tool actuator test
Likely causes
- Open circuit in the bypass valve control wire, so the driver never sees the coil pull the line down
- Corroded, spread or backed out terminals in the bypass valve connector
- Internally open solenoid winding in the EGR cooler bypass valve
- Control wire chafed against a bracket and shorted to a battery positive feed
- Missing supply feed to the valve, such as a blown fuse or an open relay contact shared with the EGR circuit
- Heavy soot build up seizing the bypass flap, which overloads and then opens the coil
- Failed PCM output driver, considered only after the harness is proven good
How to fix it
- Read the freeze frame and note coolant temperature, load and engine speed when the fault set
- Inspect the bypass valve connector for corrosion, melted plastic and loose terminals, since it sits in a hot area
- Backprobe the control circuit with a multimeter, key on: a constant supply voltage reading points to an open load
- Measure solenoid resistance across the valve terminals; an infinite reading confirms an internal open
- Check continuity from the valve connector to the PCM pin while wiggling the harness to expose intermittent breaks
- Command the valve on and off with a scan tool and watch the commanded state against the measured voltage
- Replace the EGR cooler bypass valve only after the wiring and supply are verified, then clear the code and drive a full warm up cycle