What this code means
U0199 may indicate that the keyless access control unit is not receiving expected communication from the power window master switch side of the body network.
What the vehicle may do
- The vehicle may have keyless access or body electrical symptoms.
- The code may also be stored with few obvious symptoms.
- The condition can be intermittent if a connection drops in and out.
Possible fault areas
- Possible power or ignition feed issue at the power window master switch.
- Possible ground issue at the power window master switch.
- Possible fuse or fuse-circuit issue.
- Possible open or poor connection in B-CAN wiring between the keyless access control unit and the power window master switch.
Diagnostic path
Opening and diagnostic frame
On this 2010 to 2016 Honda CR-V with the 2.4 gas engine, U0199 is a keyless access communication fault tied to the power window master switch side of the body network. In plain language, the keyless access control unit may not be seeing the expected communication from that power window unit. Depending on the failure, the vehicle may show keyless access or other body-electrical symptoms, or it may only store the code. The broad fault areas are possible power or ignition feed to the power window master switch, possible ground trouble, possible fuse trouble, or a possible open or poor connection in the B-CAN wiring between the keyless access control unit and the power window master switch. If other body-network codes are present, do not treat this one by itself. Check what those codes mean first, then come back to U0199 if it still applies.
Verify the code first
Start by proving the fault is active. Clear the codes with the HDS. Turn the vehicle OFF, then back ON, wait for at least 6 seconds, and check for codes again. If U0199 comes right back, continue into the circuit checks. If it does not come back, treat it as an intermittent at this point. The system is OK right now, so look closely for loose terminals, poor connector fit, or connection issues that could drop in and out.
Use the network status to choose the path
Next, use the HDS to check the connected B-CAN control unit information. You are looking at the detect status for the power window unit. If the power window unit is shown as detected, skip ahead to the B-CAN line continuity check between the keyless access control unit and the power window master switch. If it is not detected, stay in order and check the power, fuse, and ground side of the power window master switch first.
Check the fuses before measuring the switch feeds
For the not-detected path, check the two fuses that feed this part of the circuit: No. A29, 10 A, in the under-hood fuse and relay box, and No. B22, 7.5 A, in the under-dash fuse and relay box. If both fuses are OK, move on to the power feed tests at the power window master switch connector. If a fuse is not OK, replace the fuse. If it blows again, repair the short to ground in the No. A29, 10 A, or No. B22, 7.5 A fuse circuit as applicable.
Check the constant feed
With the vehicle OFF, disconnect the power window master switch 37P connector. Measure voltage from terminal No. 26 at that connector to body ground. This is the +B BACK UP line check. If you have battery voltage there, that feed is OK and you continue to the ignition feed. If you do not have battery voltage, repair the open or high resistance in that wire.
Check the ignition feed
Now turn the vehicle ON, with the power window master switch 37P connector still disconnected. Measure voltage from terminal No. 25 to body ground. This checks the IG2 A/C line. If battery voltage is present, that wire is OK and you move to the ground checks. If battery voltage is not present, repair the open or high resistance in that wire.
Check the grounds
Turn the vehicle back OFF. With the power window master switch 37P connector disconnected, check continuity to body ground on terminal No. 3, and then on terminal No. 31. If both ground paths have continuity, the ground wires are OK and the diagnosis moves to the B-CAN wiring. If continuity is missing, repair the open or high resistance in the ground wire, or the poor ground at G501.
Check the B-CAN wiring between the modules
For the B-CAN line check, keep the vehicle OFF and disconnect both the power window master switch 37P connector and keyless access control unit connector B, the 28P connector. Check continuity between power window master switch connector terminal No. 28 and keyless access control unit connector B terminal No. 6. This same B-CAN continuity check is used after the power and ground path, and also when the power window unit was detected earlier. If continuity is present, the fault points to an open or poor connection in the B-CAN_L wire between the keyless access control unit and the power window master switch. If continuity is not present, the fault points to an open or poor connection in the B-CAN_H wire between those same two units.
Verify the repair
After any wiring, fuse circuit, ground, or connector repair, keep verification separate from testing. Clear the code, cycle the vehicle through the same OFF-to-ON check, wait for at least 6 seconds, and confirm U0199 does not reset. The takeaway is simple: prove the code first, use the power window unit detect status to choose the path, then separate power, ground, and B-CAN wiring faults without guessing. For more diagnostic training, visit stepdiagnostics.com.
Final check
For U0199, the diagnostic logic is to confirm the code, check whether the power window unit is detected on the body network, then isolate power, ground, fuse, and B-CAN wiring faults in order.
For more guided automotive diagnostics, visit STEP Diagnostics.
