P2143 indicates the powertrain control module (PCM) has detected an open circuit in the electrical path controlling the Exhaust Gas Recirculation (EGR) vent solenoid. This solenoid regulates vacuum signals to the EGR valve, and an open circuit prevents the PCM from commanding EGR flow. The fault may reside in the solenoid itself, the connecting wiring, or—rarely—the PCM driver circuit.
The solenoid's internal coil winding opens electrically due to age, heat, or vibration, creating infinite resistance and breaking the control circuit.
The control wire between the PCM and solenoid may be broken, chafed, or disconnected by previous repairs or rodent damage.
Terminal pins at the solenoid or PCM connector may corrode, back out of the housing, or sustain damage that interrupts electrical continuity.
The solenoid's return path to ground may be compromised by loose grounds, corroded eyelets, or wire damage, preventing current flow.
The PCM's internal transistor that switches the solenoid ground may fail, though this is statistically uncommon compared to external component faults.
Short-term driving is usually safe, though the engine may produce higher combustion temperatures and NOx emissions without functioning EGR.
PCM failure causing this code is uncommon; the vast majority of cases are resolved by replacing the solenoid or repairing wiring. The PCM should only be considered after all external circuits and the solenoid have been verified as good.
It is an electronically controlled valve that vents or blocks vacuum to the EGR valve diaphragm, allowing the PCM to precisely control exhaust gas recirculation flow based on engine load and temperature.
It is unlikely to cause immediate mechanical damage, but prolonged operation without EGR can lead to excessive combustion chamber temperatures and increased NOx production.