What this code means
P0848 may indicate the PCM is seeing a high signal from the transmission fluid pressure switch B circuit for the 3rd clutch.
What the vehicle may do
- The transmission may go into a fail-safe strategy.
- The vehicle can be limited to higher-gear operation rather than shifting normally.
- The concern may be intermittent if the condition is not present during testing.
Possible fault areas
- A possible 3rd clutch pressure switch concern.
- Possible poor connector contact or loose terminals between the switch and the PCM.
- A possible open in the OP3SW signal wire.
- A possible PCM-side circuit concern after the switch and wiring path check OK.
Diagnostic path
Open and setup
On this Accord, P0848 is for the transmission fluid pressure switch B circuit, the 3rd clutch pressure switch. In plain language, the PCM may be seeing that switch signal stay high when the operating condition says it should be doing something else. The driver may notice the transmission protecting itself; with this code stored, it can be limited to 3rd through 5th gear by fail-safe. The broad fault areas are the 3rd clutch pressure switch, its connector and terminals, the OP3SW signal wire back to the PCM, or, after the circuit checks pass, the PCM side of the circuit. Before getting into the pinpoint checks, start with the basic system checks so you are not chasing a low-voltage, connector, or scan-tool setup problem.
First, try to duplicate the fault
Start by turning the vehicle to ON mode and clearing the code with the HDS. Raise the vehicle on a lift, make sure it is securely supported, and make sure all four wheels can rotate freely. Start the engine, then disable VSA with the VSA OFF button. If vehicle speed will be above 31 mph (50 km/h), use VSA maintenance mode. Now run the vehicle in 3rd gear and watch the 3rd Pressure Switch parameter on the HDS. The threshold you are checking against is 3rd Pressure Switch ON. After the check, slow down and stop the wheels.
Interpret the first result
If the current condition matches that threshold in 3rd gear, treat it as an intermittent at this point. The system is OK right now, so concentrate on poor connections and loose terminals between the 3rd clutch pressure switch and the PCM. If captured data exists for the code, try to reproduce the captured conditions instead of guessing. If the condition does not match the threshold, the fault has been duplicated, so move on to isolating the switch from the rest of the circuit.
Check whether the switch area is the failure point
Turn the vehicle to OFF, then disconnect the transmission fluid pressure switch B, the 3rd clutch switch, 1P connector. Install a jumper between connector No. 1, the LT BLU wire, and body ground. Turn the vehicle back to ON mode and check the 3rd Pressure Switch parameter with the HDS again. The question is still whether the current condition matches the 3rd Pressure Switch ON threshold.
Interpret the jumper test
If the parameter now matches the threshold with that jumper in place, the diagnostic path calls for replacing transmission fluid pressure switch B, the 3rd clutch switch. If it does not match the threshold, leave the switch alone for now and continue into the OP3SW wire check.
Check the OP3SW signal wire for an open
Turn the vehicle to OFF again and remove the jumper wire. Jump the SCS line with the HDS, then disconnect PCM connector B, the 51P connector. Now check continuity between the 3rd clutch pressure switch connector No. 1, the LT BLU wire, and PCM connector B terminal No. 25, also LT BLU. This continuity check is done with the vehicle in OFF mode, the switch connector disconnected, and PCM connector B disconnected.
Interpret the OP3SW wire check
If there is continuity, the OP3SW wire checks OK, and the diagnostic path calls for replacing the PCM. If there is no continuity, repair the open in the OP3SW wire between transmission fluid pressure switch B and the PCM. Keep this decision tied to the test result; do not jump ahead to a module or switch call before the circuit result points there.
Close
The clean way through P0848 is to duplicate the pressure-switch logic first, use the jumper test to separate the switch from the circuit, then prove the OP3SW wire before making the final call. Verify the repair separately and confirm the code stays gone. For more diagnostic training, visit stepdiagnostics.com.
Final check
Duplicate the switch signal problem first, then isolate the switch, wire, and PCM side in order.
For more guided automotive diagnostics, visit STEP Diagnostics.
