What this code means
B1038 may mean the body control module is not receiving an immobilizer authentication ID message over the F-CAN network.
What the vehicle may do
- The vehicle may show security or immobilizer-related behavior.
- The vehicle may have starting or authorization concerns depending on how the communication fault is occurring.
- The code can also be stored while other network communication concerns are present.
Possible fault areas
- A transmitting control unit that may not be starting normally.
- Possible power or ground trouble at the transmitting control unit.
- Possible CAN gateway or F-CAN communication path concerns.
- Possible wiring, connector, body control module, or VSA modulator-control unit involvement.
Diagnostic path
Open and frame the fault
Today we’re looking at B1038 on a 2020 to 2025 Honda CR-V Hybrid. In plain terms, the body control module may not be receiving the immobilizer authentication ID over the F-CAN network. The driver may notice security or starting-related behavior, or the vehicle may simply store the code while the network concern is being diagnosed. Broadly, this can involve a control unit that is not waking up correctly, a power or ground issue at the transmitting unit, a CAN gateway or F-CAN communication path problem, or one of the modules on that path. We’re going to keep this diagnosis organized and avoid jumping straight to a module call.
Start with the setup checks
Start with the basic system checks and follow a structured diagnostic approach. If other codes are present, especially communication-related codes, handle those in the proper multiple-code order first. For this code, use the code shown on the scan tool display to stay on the correct path, then inspect the involved connectors and terminals carefully. Before going into the F-CAN circuit checks, check the power and ground circuit of the transmitting control unit first, because this code may set if that unit does not start normally or loses the power or ground it needs.
Confirm the condition
For the confirmation step, turn the vehicle to the ON mode. Keep this separate from the circuit testing. The confirmation step establishes the operating state; the circuit checks are where we start proving whether the network wiring and connected units are behaving normally.
Check the BF-CAN open wire path
Next, check the BF-CAN high and low circuits for an open. With the vehicle set up for the test, disconnect the CAN gateway connector, which is the 40P connector, and disconnect body control module connector A, which is the 66P connector. Then perform the open wire inspection for BF-CAN_H and BF-CAN_L with IG Mode OFF. Each side should measure less than 1 Ω. If either result is abnormal, treat that as a problem in the circuit and stay with the wiring and connection path instead of condemning a control unit.
Check the VF-CAN A open wire path
After that, move to the VF-CAN A high and low circuits. Disconnect the CAN gateway connector, again the 40P connector, and disconnect the VSA modulator-control unit connector, which is the 46P connector. Perform the open wire inspection for VF-CAN A_H and VF-CAN A_L with IG Mode OFF. The normal result for each circuit is less than 1 Ω. If either side is abnormal, the fault is in that circuit path, so correct that direction before moving on.
Use the connected unit check for the body control module
Once the external circuit checks are normal, inspect body control module communication using the HDS F-CAN Bus Connected Unit Check. The expected result is that the body control module is shown as Detected on BF-CAN. If that check is abnormal, the path points to a problem with the body control module. One important note: this connected unit check can be done before the individual inspections because it covers all of the inspection items, but if it fails, continue through the individual checks to find which item actually failed.
Evaluate the remaining VSA path
If the other inspection items have all shown normal results, the remaining direction is the VSA modulator-control unit. At that point, the diagnostic result is a problem with the VSA modulator-control unit. The key is that this conclusion comes after the power and ground checks, the communication-priority checks, the BF-CAN circuit check, the VF-CAN A circuit check, and the body control module connected-unit check have been worked in order.
Close
The takeaway on B1038 is simple: prove the network and module wake-up conditions first, prove the BF-CAN and VF-CAN A wiring with the specified low-resistance checks, then use the connected-unit result to separate a body control module direction from the remaining VSA direction. Don’t guess at modules before the circuit path is proven. For more diagnostic training, visit stepdiagnostics.com.
Final check
B1038 is often best approached as a communication-path diagnosis: confirm the operating state, prove power and ground direction first, then prove the network wiring before making a module-level call.
For more guided automotive diagnostics, visit STEP Diagnostics.
