What this code means
B0090 may indicate that the SRS unit is not receiving the expected signal from the left front impact sensor circuit.
What the vehicle may do
- The SRS warning light may be on.
- The supplemental restraint system may have limited fault protection while the fault is active.
Possible fault areas
- A possible connector fit or terminal issue in the left front impact sensor circuit.
- A possible wiring problem between the SRS unit and the left front impact sensor.
- A possible left front impact sensor issue.
- A possible SRS unit software or SRS unit concern after circuit checks are completed.
Diagnostic path
Opening context
On this 2010 to 2016 Honda CR-V, B0090 is an SRS code for no signal from the left front impact sensor circuit. In plain terms, the SRS unit may not be seeing the left front impact sensor the way it expects to. The vehicle may turn on the SRS warning light, and the supplemental restraint system may have limited fault protection while the fault is active. The possible fault areas can include connector fit, wiring between the SRS unit and the left front impact sensor, the sensor itself, and in some cases SRS unit software or the SRS unit after the circuit checks are finished. Because this is an SRS circuit, start by checking whether the vehicle was in a collision. If it was, make sure the required SRS components were replaced with the correct new parts and installed correctly. Also handle the battery disconnect and SRS precautions correctly before touching connectors or doing resistance checks.
Confirm the code first
Start by verifying the problem. Clear the codes with the HDS, turn the vehicle to the ON mode, and wait for 10 seconds. Then check codes again with the HDS. If B0090-87 comes right back, the failure is duplicated and you move into the circuit checks. If it does not come back, treat it as an intermittent at this time. If other codes are present, check what they mean first instead of chasing this circuit by itself.
Connector check before meter work
Next, turn the vehicle to the OFF, LOCK mode and inspect the connector path. Check SRS unit connector A, 39P, the left front impact sensor 2P connector on the engine compartment wire harness, and the connector between the SRS unit and the left front impact sensor. If the connectors are clean, tight, and properly seated, continue to the wire checks. If a poor connection is found, repair that connector issue first.
Recheck after connector repair
After repairing a poor connector connection, clear the codes with the HDS, turn the vehicle to the ON mode, wait for 10 seconds, and check for codes again. If B0090-87 is still indicated, turn the vehicle back to OFF, LOCK mode and continue into the wiring tests. If the code does not return, the system is OK at this time.
Check for LFS plus to LFS minus short
Before the resistance checks, disconnect the negative cable from the 12 volt battery and wait at least 3 minutes. Then disconnect SRS unit connector A, 39P, and the left front impact sensor 2P connector on the engine compartment wire harness. With both ends disconnected, measure resistance between SRS unit connector A terminal No. 28 and terminal No. 29. You are looking for an open circuit, or at least 1 MΩ. If that result is present, the LFS plus and LFS minus wires are not shorted together, so continue. If not, the fault is a short to another wire in the engine compartment wire harness or dashboard wire harness; repair by replacing the faulty harness, then clear the code.
Check for short to ground
With the same connectors still disconnected and the vehicle still in OFF, LOCK mode, check each LFS line to body ground. Measure from SRS unit connector A terminal No. 28 to body ground, and then from terminal No. 29 to body ground. The expected result is an open circuit, or at least 1 MΩ. If both lines pass, continue. If either line does not pass, the fault is a short to ground in the engine compartment wire harness or dashboard wire harness; replace the faulty harness, then clear the code.
Check for short to power
Now reconnect the negative cable to the 12 volt battery and turn the vehicle to the ON mode. Keep SRS unit connector A, 39P, and the left front impact sensor 2P connector disconnected. Measure voltage from terminal No. 28 to body ground, and then from terminal No. 29 to body ground. The spec is 0.2 V or less. If both circuits are at 0.2 V or less, the LFS lines are not shorted to power, so move on to the open-circuit check. If either circuit is above that, the fault is a short to power in the engine compartment wire harness or dashboard wire harness; replace the faulty harness, then clear the code.
Check for an open in the LFS lines
For the open-wire check, turn the vehicle back to OFF, LOCK mode. Connect the black terminal of SRS simulator lead L to the SRS inflator simulator, then connect SRS simulator lead L to the left front impact sensor 2P connector on the engine compartment wire harness. With SRS unit connector A still disconnected, measure resistance between terminal No. 28 and terminal No. 29 at SRS unit connector A. The expected result is 1.0 Ω or less. If it is not 1.0 Ω or less, there is an open in the engine compartment wire harness or dashboard wire harness; replace the faulty harness, then clear the code.
If the circuit checks pass
If the open-wire check shows 1.0 Ω or less, the LFS plus and LFS minus wires are OK. At that point, replace the left front impact sensor, clear the code, and retest. If the code still returns after that, pause, recheck the earlier diagnostic path, and avoid guessing. Before any SRS unit replacement is considered, check the SRS unit software version with the HDS. If the software is not the latest version, update the SRS unit software and retest.
Close
The takeaway on B0090 is simple: prove the code is current, handle connector issues first, then isolate the left front impact sensor circuit for shorts together, shorts to ground, shorts to power, and opens before condemning the sensor or moving any farther. For more diagnostic training, visit stepdiagnostics.com.
Final check
B0090 is often approached as a circuit diagnosis first: verify the code, check connectors, then test the sensor wiring before moving beyond the circuit.
For more guided automotive diagnostics, visit STEP Diagnostics.
