What this code means
P0966 may indicate a possible electrical fault in the A/T clutch pressure control solenoid valve B control circuit.
What the vehicle may do
- The vehicle may shift harshly or feel abnormal during automatic transmission operation.
- A transmission warning or check engine light may be present.
- The transmission can sometimes use a protective strategy when solenoid control is not trusted.
Possible fault areas
- A/T clutch pressure control solenoid valve B circuit
- Possible connector or terminal issues
- Possible ground-side fault
- Possible LINEAR_B control wire fault
- Possible PCM control or software-related issue
Diagnostic path
Opening context
On this 2010 to 2015 Honda Civic with the 1.8, P0966 points us toward the A/T clutch pressure control solenoid valve B circuit. In plain terms, the PCM may be seeing an open or short in the electrical side of that solenoid control. The car may shift harshly, go into a protective strategy, or simply store the code with a transmission warning. Broadly, think possible solenoid circuit trouble, connector or terminal issues, ground trouble, LINEAR_B wire trouble, or PCM control issues. Before you troubleshoot, save all freeze data and any on-board snapshot with the HDS. Also, for this code path, treat this as an electrical circuit problem, not a mechanical problem inside the transmission.
Verify whether the fault is present now
Start by turning the ignition switch to ON (II). Clear the DTC with the HDS, start the engine, and wait for at least 1 second. Then check Pending and Confirmed DTCs with the HDS. If P0966 comes right back, the failure is duplicated and you move straight into the solenoid circuit checks. If it does not come back, use the HDS to run the A/T clutch pressure control solenoid valve B operation check from the Miscellaneous Test Menu.
Use the scan tool to try to duplicate the problem
During the solenoid operation check, if the HDS shows NORMAL, the solenoid passes that functional check, so keep going and try to duplicate the code under command. In the clutch pressure control solenoid valve control menu, command A/T clutch pressure control solenoid valve B at 1.0 A, then watch the OBD STATUS for P0966 in the DTC menu. If the status shows FAILED, the failure is duplicated and you continue with circuit testing. If it shows PASSED, treat it as intermittent for now; the system is OK at this time, so inspect for poor connections or loose terminals between the solenoid valve and the PCM. If it shows NOT COMPLETED, run the drive again until the monitor completes.
Check solenoid internal resistance
Once the failure is duplicated, or if the solenoid operation check does not show NORMAL, turn the ignition switch to LOCK (0). Disconnect the A/T clutch pressure control solenoid valve B 2P connector. Measure resistance between connector No. 1 and connector No. 2, across the GND and LINEAR_B sides of the solenoid. The expected resistance is 5.0－6.3 Ω. If the measurement is in that range, the solenoid itself is OK and you move on to the ground circuit. If it is not in that range, replace A/T clutch pressure control solenoid valve B, then verify the repair.
Check the solenoid ground side
With the ignition still at LOCK (0) and the solenoid 2P connector disconnected, check continuity on the ground side. Check from A/T clutch pressure control solenoid valve B connector No. 1, the BLK wire, to body ground. If you have continuity, the ground wire is OK and you continue to the LINEAR_B short-to-ground check. If you do not have continuity, repair the open in the ground wire between the solenoid and ground G101, or repair the poor ground at G101, then verify the repair.
Check the LINEAR_B circuit for a short to ground
Next, keep the ignition at LOCK (0). Jump the SCS line with the HDS, then disconnect PCM connector B, the 49P connector. With the solenoid connector still disconnected, check continuity from A/T clutch pressure control solenoid valve B connector No. 2, the BRN wire, to body ground. If there is continuity, the LINEAR_B wire is shorted to ground between the solenoid and the PCM; repair that short, then verify the repair. If there is no continuity, the LINEAR_B wire is not shorted, so continue to the open-circuit check.
Check the LINEAR_B circuit for an open
Now check continuity through the LINEAR_B wire itself. With the ignition at LOCK (0), the solenoid 2P connector disconnected, and PCM connector B disconnected, check from A/T clutch pressure control solenoid valve B connector No. 2, the BRN wire, to PCM connector B 49P terminal No. 8, also BRN. If there is no continuity, repair the open in the LINEAR_B wire between the solenoid and the PCM, then verify the repair. If there is continuity, the LINEAR_B wire is OK. At that point, update the PCM if it does not have the latest software, or substitute a known-good PCM, then move into repair verification.
Verify the repair separately
For verification, reconnect all connectors. Turn the ignition switch to ON (II), clear the DTC with the HDS, start the engine, and wait for at least 1 second. Then monitor the OBD STATUS for P0966 in the DTC menu. If the HDS shows PASSED, troubleshooting is complete. If a known-good PCM was substituted, replace the original PCM. After that, check for other DTCs; if any other Pending or Confirmed codes are present, check what they mean next. If the HDS shows FAILED, go back to the beginning and recheck the path. If the PCM was updated, substitute a known-good PCM and check OBD STATUS again. If the HDS shows NOT COMPLETED, meet the test condition and check OBD STATUS again.
Takeaway
The key on P0966 is to prove whether the fault is current, then separate the solenoid, ground, LINEAR_B wiring, and PCM control side without guessing. Keep the verification step separate, and let the OBD STATUS tell you whether the repair actually held. For more diagnostic training, visit stepdiagnostics.com.
Final check
P0966 is often approached as a circuit diagnosis: verify the code, check solenoid operation, test the solenoid and wiring, then confirm the repair with OBD STATUS.
For more guided automotive diagnostics, visit STEP Diagnostics.
