P2154 indicates the powertrain control module (PCM) has detected an unexpectedly high voltage on the supply/control circuit for Fuel Injector Group C. Group C refers to a specific group of injectors pulsed together by the ECM, and an abnormally high reading typically means the circuit is not completing properly back to ground. The condition is most often a wiring or connector issue rather than an internal ECM fault.
A broken, chafed, or disconnected wire in the harness feeding the affected injector group prevents normal current flow, causing the ECM to read back a high (un-pulled-down) voltage on the circuit.
A poor connection at the injector plug—often from heat cycling, vibration, or moisture—creates a high-resistance or open condition that the ECM interprets as excessive supply voltage.
If the internal coil winding of one of the injectors in Group C has burned open, current cannot flow, and the control circuit will read high. Ohm-testing each injector in the group is appropriate.
Insulation damage allowing a Group C control wire to contact a powered circuit can force voltage onto the injector line. Less common than a plain open, but possible in damaged or aftermarket-wired harnesses.
Poor contact where the injector harness meets the PCM—corrosion, bent pins, or a cracked connector—can produce the same high-voltage feedback condition.
Rare, but a failed output driver in the PCM controlling Group C can produce incorrect voltage readings. This is statistically uncommon and should only be considered after wiring and injectors have been ruled out.
Technically yes, but it is the least common cause. In the vast majority of cases, P2154 is traced to a wiring fault, connector issue, or failed injector coil. Replacing the PCM without first verifying the harness and injectors is a frequent and costly misdiagnosis.
Short trips at low load are usually possible, but the affected cylinder(s) will run lean or dead, which can overheat the catalyst over time and cause additional misfire-related damage. Repair as soon as practical.
Not necessarily. Diagnosis typically identifies a single open injector within the group; only that unit needs replacement unless others also fail resistance testing.
Indirectly, yes. A poor engine or chassis ground can alter reference voltages and contribute to high-circuit readings. Grounds should be inspected as part of the wiring check, but they are rarely the sole cause.