What this code means
P0966 may indicate an electrical fault in the transmission control circuit for A/T clutch pressure control solenoid valve B.
What the vehicle may do
- The vehicle may enter a fail-safe strategy.
- Shift operation may be limited when the code is stored.
Possible fault areas
- Possible fault areas can include the LSB control wire, the PG ground circuit, connector or terminal issues, the solenoid valve assembly, or PCM-side control after the circuit and A
- solenoid checks are proven.
Diagnostic path
Set the diagnostic frame
On this 2010 to 2017 Honda Accord with the 2.4 gas engine, P0966 may point to an electrical problem in the transmission control circuit for A/T clutch pressure control solenoid valve B. The car may go into fail-safe, and when this code is stored it does not shift to any gear other than 1st, 2nd, or 5th. Possible fault areas can include the LSB control wire, the PG ground circuit, connector or terminal issues, the solenoid valve assembly, or PCM-side control after the circuit and solenoid checks are proven. Keep the diagnosis electrical: this code is not caused by a mechanical problem inside the transmission. Before getting into circuit checks, save the freeze data and any on-board snapshot with the HDS. That gives you the conditions the PCM saw when it flagged the fault.
Verify the problem first
Start by selecting ON mode with the engine start/stop button. Clear the code with the HDS, then check for pending or confirmed codes. If P0966 comes right back, the failure is duplicated and you can move into circuit testing. If it does not come back, treat it as intermittent for now. The system is OK at this time, so concentrate on poor connections or loose terminals between A/T clutch pressure control solenoid valve B and the PCM.
Check the LSB circuit for a short to ground
Next, select OFF mode, jump the SCS line with the HDS, and disconnect PCM connector B, the 51P connector. Check continuity on the LSB circuit from PCM connector B, terminal No. 7, the PUR wire, to body ground. If you have continuity there, continue with the shorted-wire check at the solenoid end. If you do not have continuity there, skip ahead to the LSB open-circuit check.
Isolate the shorted LSB wire path
For the shorted-wire check, keep the vehicle in OFF mode with PCM connector B disconnected, and disconnect the A/T clutch pressure control solenoid valve B 2P connector. Check continuity from terminal No. 2 at that solenoid connector, the PUR wire, to body ground. If continuity is still present, repair the short to body ground in the LSB wire between A/T clutch pressure control solenoid valve B and the PCM. If continuity is gone at this point, the LSB wire is OK, and the diagnostic path calls the A/T clutch pressure control solenoid valve B faulty. The repair direction there is to replace the secondary valve body, which includes A/T clutch pressure control solenoid valve B.
Check the LSB circuit for an open
If the first LSB check did not show a short to ground, check the LSB wire for an open. With OFF mode selected, the solenoid valve B 2P connector disconnected, and PCM connector B disconnected, check continuity from solenoid connector terminal No. 2, the PUR wire, to PCM connector B terminal No. 7, also the PUR wire. If there is continuity, the LSB wire is OK and you move on to the PG circuit. If there is no continuity, repair the open in the LSB wire between A/T clutch pressure control solenoid valve B and the PCM.
Check the PG ground circuit
Now check the PG circuit. With the same connectors still disconnected and OFF mode selected, check continuity from terminal No. 1 at the A/T clutch pressure control solenoid valve B 2P connector, the BLK wire, to body ground. If continuity is present, the PG wire is OK and you can test the solenoid resistance. If continuity is missing, the diagnostic path points to an open in the PG wire between A/T clutch pressure control solenoid valve B and body ground G101, or a poor body ground. The ground callout is incomplete here, so do not guess at an exact ground location beyond what is identified. Pause, recheck the earlier diagnostic path and ground information, and repair only what you can confirm.
Measure solenoid valve B resistance
If both the LSB and PG wiring checks pass, measure resistance across A/T clutch pressure control solenoid valve B at the 2P connector, between terminal No. 1 and terminal No. 2. The expected result is 4.7－5.9 Ω. If the measurement is in that range, A/T clutch pressure control solenoid valve B is OK, and the diagnostic path calls for PCM replacement. If the measurement is not 4.7－5.9 Ω, the solenoid valve B is faulty, and the repair direction is to replace the secondary valve body, which includes A/T clutch pressure control solenoid valve B.
Wrap-up
The key on P0966 is to stay disciplined: verify the code, separate a shorted LSB circuit from an open LSB circuit, confirm the PG ground path, and only then judge the solenoid resistance. Keep final verification separate from the circuit testing, and make sure the repair is confirmed before closing the job. For more diagnostic training, visit stepdiagnostics.com.
Final check
This diagnosis is mainly about proving the wiring and solenoid circuit condition before condemning a control component.
For more guided automotive diagnostics, visit STEP Diagnostics.
