What this code means
P16E2 may indicate a communication problem on the LIN line used between the PCM and the charging-system control side.
What the vehicle may do
- The vehicle may show a charging-system or battery-related warning.
- The customer may notice intermittent charging behavior.
- The vehicle can also have very little obvious driveability complaint.
Possible fault areas
- Possible LIN circuit wiring fault.
- Possible poor connection or loose terminal at the alternator, battery sensor, or PCM.
- Possible alternator-side issue.
- Possible PCM software or PCM-side issue.
Diagnostic path
Opening context
On this 2010 to 2015 Honda Civic with the 1.8 gas engine, P16E2 is a PGM-FI to ACG LIN communication problem. In plain terms, the PCM may not be seeing the communication it expects on the LIN line tied into the charging system. The vehicle can have charging-system complaints, battery-related symptoms, or it may come in with the light on and very little driver complaint. The broad fault areas are possible LIN wiring trouble, connector or terminal issues at the alternator, battery sensor, or PCM, and in some paths a possible alternator or PCM-side problem. Before diving in, start with the basic system checks and keep the diagnosis structured.
Verify the code first
Start by turning the ignition switch ON, or selecting ON mode with the engine start/stop button. Clear the code with the HDS, wait 10 seconds, then check for pending or confirmed codes again. If P16E2 does not come back, treat it as an intermittent at this time. Check closely for poor connections or loose terminals at the alternator, the battery sensor, and the PCM. If captured operating data is available, try to reproduce the same conditions instead of guessing. If P16E2 is indicated again, continue with the next check.
Use the companion-code direction without turning it into a parts call
Next, check pending or confirmed codes with the HDS again and look for the companion code from this same diagnostic path. If that companion code is present, the path moves toward checking whether the LIN circuit is shorted. If it is not present, the path moves straight to the LIN open-circuit check between the alternator and the PCM.
If the path points toward a shorted LIN circuit
With the ignition in LOCK, or the vehicle in OFF mode, disconnect the battery sensor 2P connector. Check continuity on the LIN circuit between battery sensor 2P connector terminal No. 2, the green wire, and body ground. If there is continuity, keep going with the shorted-wire isolation. If there is no continuity, the path moves to the later open-wire check.
Isolate the short if continuity to ground is present
Jump the SCS line with the HDS. Keep checking continuity between battery sensor 2P connector terminal No. 2 and body ground while disconnecting the alternator 1P connector and PCM connector B, the 51P connector, one at a time. If continuity goes away when one of those connectors is disconnected, the LIN wire is considered OK on that branch, and the part that made the fault disappear is the replacement call. If continuity does not go away, repair the short in the LIN wire between the battery sensor, alternator, and PCM B31.
If the companion-code path is not present, check the LIN wire for an open
For the open-wire check, put the ignition in LOCK or the vehicle in OFF mode. Jump the SCS line with the HDS, then disconnect the alternator 1P connector and PCM connector B, the 51P connector. Check continuity on the LIN circuit between PCM connector B31, the yellow wire, and alternator 1P connector terminal No. 1, also the yellow wire. If there is continuity, the LIN wire is OK on this branch, and the alternator is the replacement call. If there is no continuity, repair the open in the LIN wire between the alternator and PCM B31.
If the earlier short check did not show continuity to ground
When the earlier battery-sensor-to-ground check did not show continuity, the path moves to another open-wire check on the LIN line. Jump the SCS line with the HDS and check continuity between PCM connector B31, yellow wire, and alternator 1P connector terminal No. 1, yellow wire. Keep the connector setup straight here: the test condition calls for the alternator 1P connector and PCM connector B to be disconnected. If the setup does not match the earlier diagnostic path, pause, recheck the path you are on, and do not guess. If there is no continuity, repair the open in the LIN wire between the alternator and PCM B31. If there is continuity, the LIN wire is OK on this branch. Update the PCM if it does not have the latest software, or substitute a known-good PCM. If P16E2 goes away after the PCM update, troubleshooting is complete. If P16E2 goes away with a known-good PCM substituted, replace the original PCM.
Closing takeaway
The key on P16E2 is to prove the LIN circuit first, then let the branch result decide whether you are dealing with a short, an open, the alternator path, or the PCM path. Keep verification separate from the circuit testing, and do not make a parts call until the continuity path supports it. For more diagnostic training, visit stepdiagnostics.com.
Final check
P16E2 is often a circuit-first diagnosis: prove the LIN line condition before making a component call.
For more guided automotive diagnostics, visit STEP Diagnostics.
