U0673 indicates that the engine control module (PCM) has lost communication with the Ion Sense Module, which monitors combustion quality via ionization current. This code is typically set when the module does not respond on the vehicle's communication network for a specified period.
Damaged, corroded, or loose pins in the module's harness connector are the most common cause, interrupting communication.
Internal electronic failure of the module itself prevents it from communicating on the network.
A break or short in the CAN bus wires (typically CAN-H and CAN-L) between the PCM and the module can cause loss of communication.
Missing battery voltage or a poor ground at the module will prevent it from powering up and communicating.
A corroded ground point or broken ground wire can cause intermittent or total communication loss.
In very rare cases, the PCM itself may have an internal communication failure, but this should only be considered after all other causes are ruled out.
No. The PCM is rarely the cause of this code. Most often the issue is a wiring problem, a bad connector, or a failed Ion Sense Module. Replacing the PCM without proper diagnosis is expensive and usually ineffective.
The Ion Sense Module detects ionization current in the engine's combustion chamber (often via the spark plug) to monitor misfires and combustion quality. It communicates this data to the PCM over the vehicle's network.
Yes. Since the module provides misfire detection data, a loss of communication can lead to incorrect fuel and ignition timing, resulting in rough idle, hesitation, and reduced performance.
You can usually drive short distances, but the vehicle may run poorly and fuel economy may suffer. Continued driving could lead to catalyst damage if misfires are present. It is best to diagnose and repair promptly.