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Subaru B22A4

If B2A20 is found in combination with U1F0188, B22A4, or B22A5, do not ignore them. Proceed with the specific trouble-tree diagnosis for those secondary codes identified in STIS. A

DriveUnknown. Verified evidence does not establish whether driving is safe with B22A4.
ChargeUnknown. Verified evidence does not establish whether charging is safe with B22A4.
ServiceService evaluation is appropriate because the verified Subaru instruction directs use of the specific STIS trouble-tree diagnosis for the detected secondary code(s).
Confidence95%

Quick answer

For Subaru vehicles in the supplied applicability data, verified evidence says B22A4 may be a secondary code that must not be ignored when B2A20 is present with U1F0188, B22A4, or B22A5. Follow the specific STIS trouble-tree diagnosis for the secondary code(s).

This page separates verified manufacturer/regulator evidence from supporting material. Unsupported causes, repairs or safety conclusions are not guessed.

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1. What does B22A4 mean?

For Subaru vehicles in the supplied applicability data, verified evidence says B22A4 may be a secondary code that must not be ignored when B2A20 is present with U1F0188, B22A4, or B22A5. Follow the specific STIS trouble-tree diagnosis for the secondary code(s).

2. Technical explanation

The supplied official Subaru manufacturer communications describe a complex-DTC situation: when B2A20 is found in combination with U1F0188, B22A4, or B22A5, the secondary code(s) should not be ignored. The documented direction is to proceed with the specific trouble-tree diagnosis in Subaru Technical Information System (STIS) for those secondary codes. The evidence does not define a component failure, root cause, or standalone functional meaning for B22A4.

3. What system is affected?

Not yet established by verified evidence.

4. How serious is this code?

Unknown. Verified evidence does not assign a severity level.

5. Symptoms you may notice

  • Not yet established by verified evidence.

6. Possible causes

  • Not yet established by verified evidence.

7. Can I still drive the vehicle?

Unknown. Verified evidence does not establish whether driving is safe with B22A4.

8. Can I charge the vehicle?

Unknown. Verified evidence does not establish whether charging is safe with B22A4.

9. What you can safely do

  • Have a qualified Subaru service professional review all stored DTCs, including any B2A20, U1F0188, B22A4, and B22A5 combination.
  • Use the applicable Subaru STIS trouble-tree diagnosis for the detected secondary code(s).
  • Do not disregard B22A4 when it is stored with B2A20.

10. Step-by-step troubleshooting

  1. Confirm whether B2A20 is present together with U1F0188, B22A4, or B22A5.
  2. For the detected secondary code(s), proceed with the specific STIS trouble-tree diagnosis as directed by the official manufacturer communication.
  3. Further diagnostic steps are not established by the supplied verified evidence.

11. When to contact service

Service evaluation is appropriate because the verified Subaru instruction directs use of the specific STIS trouble-tree diagnosis for the detected secondary code(s).

12. What the service center may check

  • Retrieve and review all diagnostic trouble codes.
  • Determine whether B2A20 is present in combination with U1F0188, B22A4, or B22A5.
  • Perform the applicable STIS trouble-tree diagnosis for the identified secondary code(s).

13. Possible repair or resolution

  • A specific repair is not established by verified evidence. Resolution depends on the result of the applicable STIS trouble-tree diagnosis.

14. Affected vehicles

15. Related TSBs / service bulletins

  • Subaru manufacturer communication 07-240-26R, published April 30, 2026; NHTSA document MC-11032034-0001.
  • Subaru manufacturer communication 07-240-26R, published February 25, 2026; NHTSA document MC-11029347-0001.

16. Recall information

  • No recall information was supplied in the verified evidence.

17. Official manufacturer information

Official evidence supplied: Subaru manufacturer communication 07-240-26R, available through NHTSA. It states that if B2A20 is found in combination with U1F0188, B22A4, or B22A5, the secondary codes should not be ignored and the applicable STIS trouble-tree diagnosis should be followed.

19. Frequently asked questions

What does the verified evidence say to do when B22A4 appears with B2A20?

Do not ignore B22A4. Proceed with the specific STIS trouble-tree diagnosis for the identified secondary code(s).

Does the evidence identify the failed part causing B22A4?

No. A failed part or root cause is not established by the supplied verified evidence.

Is B22A4 safe to drive or charge with?

Not yet established by verified evidence.

20. Sources & verification

Verified
Subaru B22A4: If B2A20 is found in combination with U1F0188, B22A4, or… | EV Diagnostics