What this code means
U0122 can indicate that the BCM is not receiving specified data from the VSA modulator-control unit.
What the vehicle may do
- The BCM may not receive specified data from the VSA unit.
- The code may be stored if the VSA unit does not start normally.
Possible fault areas
- Possible fault areas include the VSA unit’s power/ground circuit.
- The VF-CAN A_H and VF-CAN A_L circuits may have a fault.
- The VSA unit itself may have a fault.
Diagnostic path
What U0122 means
On this 2025 Honda Accord 1.5, U0122 means the body control module, or BCM, lost communication with VSA/ABS. These checks involve the VSA modulator-control unit, which we will call the VSA unit. The BCM stores this code when it cannot receive the specified data from that unit. Here is what this code tells us. The BCM may not receive specified data from the VSA unit. The code may be stored if the VSA unit does not start normally. Here are the main areas to check. Possible fault areas include the VSA unit’s power/ground circuit. The VF-CAN A_H and VF-CAN A_L circuits may have a fault. The VSA unit itself may have a fault.
Before troubleshooting U0122
Before you troubleshoot U0122, review How to Troubleshoot. If you are troubleshooting multiple DTCs, follow B-CAN System Diagnosis Test Mode A. A power/ground circuit failure at the VSA unit can store this code. Before beginning this troubleshooting, check the VSA unit’s power/ground circuit first.
U0122 identifies data the BCM did not receive; it does not, by itself, identify a failed VSA unit. The code can also be stored when the VSA unit does not start normally or has a power/ground circuit failure. That is why the power/ground check comes before this troubleshooting rather than being left until after the communication-wire checks.
Before the network checks
Troubleshoot any DTCs listed or indicated systems below first. Network Communications \[CAN gateway\]: Go to the indicated DTC's troubleshooting
Before you troubleshoot, review How to Troubleshoot. These checks cover lost communication on the F-CAN circuit connected to the CAN gateway. If the failure is intermittent or difficult to reproduce, review How to Troubleshoot (Handling Intermittent and Low Reproducibility Failures). Troubleshoot any indicated Network Communications \[CAN gateway\] DTCs first, using the troubleshooting for the indicated code.
Find the unit reporting NG
For details on using this check, review How to Troubleshoot (Handling Ongoing Failures). Use the diagnostic scanner (HDS) to run Communication Status Check of F-CAN Connected Units. Base the following inspections on the control unit whose result is NG. Check the power/ground circuit of the transmitting control unit that indicates NG.
Shared confirmation routine
The shared Confirmation Procedure is a separate routine: turn the vehicle to the ON mode. For its details, check the Confirmation Procedure for the DTC being diagnosed.
Gateway scanner function
The scanner function path is CAN Gateway ＞ Function Test ＞ Communication Status Check of F-CAN Connected Units. If the VSA Modulator-Control Unit indicates NG in that check, the following open-wire inspections apply.
The NG result selects which control unit's inspections apply; it is not yet the conclusion that the unit itself is faulty. The VSA-specific wiring branch applies when the VSA Modulator-Control Unit reports NG. The general network procedure also calls for checking the power/ground circuit of the transmitting control unit that reports NG.
Check VF-CAN A_H
For this separate open-wire inspection, IG Mode must be OFF. Both connectors must be disconnected: CAN gateway connector A (24P) and VSA modulator-control unit connector (46P). With those conditions met, check VF-CAN A_H. Place one probe on CAN gateway connector A (24P) female terminal 21. Place the other probe on VSA modulator-control unit connector (46P) female terminal 13. The resistance should be less than 1 ohm. That is the normal reading for this wire check.
Check VF-CAN A_L
For the VF-CAN A_L open-wire inspection, keep IG Mode OFF and both connectors disconnected. Place one probe on CAN gateway connector A (24P) female terminal 9. Place the other probe on VSA modulator-control unit connector (46P) female terminal 14. The resistance should be less than 1 ohm. That is the normal reading for this wire check. If the open-wire inspection results are abnormal, there is a problem in the circuit. If the results are normal, there is a problem with the VSA unit.
The circuit-versus-unit decision uses both open-wire inspection results, not the VF-CAN A_L reading alone. In this VSA NG branch, each wire must measure less than 1 ohm under the stated IG Mode OFF and disconnected-connector conditions to meet its normal condition. Abnormal inspection results identify a circuit problem; normal results direct the diagnosis to the VSA modulator-control unit.
U0122 diagnostic path
The U0122 diagnostic path calls for the F-CAN Lost Communication (CAN BUS with Connection to CAN Gateway) troubleshooting.
U0122 confirmation routine
The U0122 Confirmation Procedure is a separate routine. Turn the vehicle to the ON mode. Then wait for at least 6 seconds.
Listed scanner reference
The scanner function listed for reference is Body Electrical ＞ Lighting ＞ Data List.
More diagnostic steps
For more diagnostic steps, visit stepdiagnostics.com.
Final check
Possible fault areas include the VSA unit’s power/ground circuit, its communication wiring, and the unit itself.
For more guided automotive diagnostics, visit STEP Diagnostics.
