Mitsubishi P1A91
CMU04 balancer abnormal, P1A92: CMU05 balancer abnormal, P1A93: CMU06 balancer abnormal, P1A94: CMU07 balancer abnormal, P1A95: CMU08 balancer abnormal, P1A96: CMU09 balancer abnor
Quick answer
P1A91 is a Mitsubishi i-MiEV battery diagnostic trouble code for “CMU04 balancer abnormal.” Verified applicability is limited to U.S.-market 2012 and 2014 i-MiEV vehicles.
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 P1A91 mean?
P1A91 is a Mitsubishi i-MiEV battery diagnostic trouble code for “CMU04 balancer abnormal.” Verified applicability is limited to U.S.-market 2012 and 2014 i-MiEV vehicles.
2. Technical explanation
The verified manufacturer-service evidence groups P1A91 with battery cell-monitoring-unit (CMU) balancer abnormal codes. Specifically, P1A91 identifies CMU04. Mitsubishi service material directs diagnosis using scan tool MB991958 and a preceding battery-system test step; if that earlier test result is not normal, the stated action is replacement of the Main Drive Lithium-ion Battery. If the earlier result is normal and the DTC remains stored at the subsequent scan-tool check, the stated action is replacement of the BMU. The supplied evidence does not establish the detailed conditions that set P1A91 or a user-performable diagnostic procedure.
3. What system is affected?
Main Drive Lithium-ion Battery monitoring/balancing system, including CMU04 and the BMU.
4. How serious is this code?
Not yet established by verified evidence. The supplied diagnostic record lists severity as unknown.
5. Symptoms you may notice
- Not yet established by verified evidence.
6. Possible causes
- A CMU04 balancer abnormal condition is identified by P1A91.
- The supplied Mitsubishi service procedure distinguishes between an abnormal preceding battery-system test result, for which it specifies Main Drive Lithium-ion Battery replacement, and a stored DTC after a normal preceding result, for which it specifies BMU replacement.
- The underlying component-level cause is not yet established by verified evidence.
7. Can I still drive the vehicle?
Not yet established by verified evidence. The supplied diagnostic record lists safe-to-drive status as unknown.
8. Can I charge the vehicle?
Not yet established by verified evidence. The supplied diagnostic record lists safe-to-charge status as unknown.
9. What you can safely do
- Record the DTC and arrange diagnosis by a Mitsubishi-capable EV service facility.
- Do not attempt high-voltage battery, CMU, balancer, or BMU repair yourself.
- Use the official Mitsubishi diagnostic procedure and appropriate scan tool equipment.
10. Step-by-step troubleshooting
- Mitsubishi service evidence specifies use of scan tool MB991958 for the DTC check.
- The cited procedure refers to a preceding test step. If its result is not normal, the specified action is to replace the Main Drive Lithium-ion Battery and then continue to the scan-tool DTC check.
- If the preceding result is normal, the procedure proceeds to the scan-tool DTC check. If the DTC is stored, the specified action is to replace the BMU; if it is not stored, the check is complete.
- The details of the preceding test step are not contained in the supplied verified evidence.
11. When to contact service
Service is appropriate because the verified Mitsubishi procedure calls for EV-specific diagnostic testing and may direct replacement of either the Main Drive Lithium-ion Battery or BMU. The supplied record does not establish whether service is immediately required.
12. What the service center may check
- Confirm stored DTC status with Mitsubishi scan tool MB991958.
- Perform the preceding battery-system test specified in the applicable Mitsubishi service procedure.
- If the preceding test result is not normal, follow the cited procedure’s Main Drive Lithium-ion Battery replacement direction.
- If the preceding test result is normal but P1A91 remains stored at the scan-tool check, follow the cited procedure’s BMU replacement direction.
13. Possible repair or resolution
- Per the cited Mitsubishi procedure, an abnormal result in the preceding test step leads to replacement of the Main Drive Lithium-ion Battery.
- Per the cited Mitsubishi procedure, a stored P1A91 after a normal preceding result leads to BMU replacement.
- No other repair resolution is established by the supplied verified evidence.
14. Affected vehicles
- Mitsubishi i-MiEV · 2012 · US
- Mitsubishi i-MiEV · 2014 · US
15. Related TSBs / service bulletins
- Mitsubishi TSB-19-54-004, published March 13, 2019; NHTSA manufacturer communication MC-10158409: https://static.nhtsa.gov/odi/tsbs/2019/MC-10158409-9999.pdf
- Mitsubishi TSB-19-54-003, published March 13, 2019; NHTSA manufacturer communication MC-10158408: https://static.nhtsa.gov/odi/tsbs/2019/MC-10158408-9999.pdf
16. Recall information
- Not yet established by verified evidence.
17. Official manufacturer information
Verified official evidence is from NHTSA-hosted Mitsubishi manufacturer communications TSB-19-54-003 and TSB-19-54-004, both published March 13, 2019. Verified applicability: U.S. Mitsubishi i-MiEV model years 2012 and 2014.
19. Frequently asked questions
What does P1A91 mean on a Mitsubishi i-MiEV?
It means “CMU04 balancer abnormal,” according to the verified Mitsubishi service evidence.
Which vehicles are verified as applicable?
U.S.-market Mitsubishi i-MiEV vehicles for model years 2012 and 2014.
Can I keep driving or charging with P1A91?
Not yet established by verified evidence. Both safe-to-drive and safe-to-charge status are listed as unknown in the supplied record.
What repair does Mitsubishi specify?
The cited procedure specifies Main Drive Lithium-ion Battery replacement when its preceding test result is not normal. When that result is normal but the DTC remains stored at the scan-tool check, it specifies BMU replacement.