Chevrolet P0AC4
00) • The Transmission Fluid Temperature is greater than 104°F (40°C). • The Vehicle Speed Sensor is greater than 37 mph (60 km/h). Reprogram the Drive Motor Power Inverter Module
Quick answer
For certain 2016–2018 US Chevrolet Volt vehicles, P0AC4 is documented in GM bulletin 16-NA-400 as an ECM-stored code that requests MIL illumination under a specific diagnostic scenario. The bulletin directs trained technicians to verify freeze-frame conditions and reprogram the Drive Motor Power Inverter Module to the latest calibrations when its stated criteria are met.
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 P0AC4 mean?
For certain 2016–2018 US Chevrolet Volt vehicles, P0AC4 is documented in GM bulletin 16-NA-400 as an ECM-stored code that requests MIL illumination under a specific diagnostic scenario. The bulletin directs trained technicians to verify freeze-frame conditions and reprogram the Drive Motor Power Inverter Module to the latest calibrations when its stated criteria are met.
2. Technical explanation
Verified evidence from GM bulletin 16-NA-400 describes a condition involving DTC P0B01, P0B04, or P0807 and possible loss of propulsion. In that scenario, P0AC4 may be stored in the ECM and request MIL illumination. The bulletin instructs technicians to review Hybrid Powertrain Control Module freeze-frame information and confirm: no additional HPCM DTCs; engine run time greater than 30 minutes; transmission fluid temperature greater than 104°F (40°C); and vehicle speed sensor greater than 37 mph (60 km/h). When all stated conditions apply, the bulletin directs reprogramming the Drive Motor Power Inverter Module to the latest available calibrations. The supplied evidence does not establish that P0AC4 alone confirms this scenario.
3. What system is affected?
The verified bulletin references the ECM, Hybrid Powertrain Control Module, Drive Motor Power Inverter Module, transmission fluid temperature, and vehicle speed sensor. A single system name is not established by the supplied evidence.
4. How serious is this code?
Not yet established by verified evidence. However, the cited GM bulletin states that vehicles in the associated P0B01, P0B04, or P0807 scenario may have loss of propulsion.
5. Symptoms you may notice
- MIL illumination is supported by the bulletin when P0AC4 is stored in the ECM and requests MIL illumination.
- Possible loss of propulsion is documented for vehicles with P0B01, P0B04, or P0807 in the bulletin’s described scenario.
- No other symptoms are established by verified evidence.
6. Possible causes
- The supplied evidence identifies a calibration-related service action: reprogramming the Drive Motor Power Inverter Module when all bulletin criteria are met.
- A root cause for P0AC4 by itself is not yet established by verified evidence.
7. Can I still drive the vehicle?
Not yet established by verified evidence. The associated GM bulletin notes possible loss of propulsion for its specified P0B01, P0B04, or P0807 scenario.
8. Can I charge the vehicle?
Not yet established by verified evidence.
9. What you can safely do
- Arrange professional diagnosis by a properly trained technician.
- Record the displayed warning messages and stored codes, if available.
- Do not attempt Drive Motor Power Inverter Module programming or high-voltage system repair yourself.
10. Step-by-step troubleshooting
- A technician should review Hybrid Powertrain Control Module freeze-frame information, as specified in GM bulletin 16-NA-400.
- The bulletin criteria are: no additional HPCM DTCs; engine run time over 30 minutes; transmission fluid temperature over 104°F (40°C); and vehicle speed sensor over 37 mph (60 km/h).
- If all bulletin criteria apply, the bulletin directs reprogramming the Drive Motor Power Inverter Module to the latest available calibrations.
11. When to contact service
Contact a Chevrolet dealer or qualified EV service facility for diagnosis. GM’s bulletin states that its bulletins are intended for professional technicians, not do-it-yourself repairers.
12. What the service center may check
- Check whether the vehicle is a 2016–2018 Chevrolet Volt in the US.
- Retrieve and assess all stored DTCs, including whether P0B01, P0B04, or P0807 is present.
- Review HPCM freeze-frame data for the conditions specified in bulletin 16-NA-400.
- Confirm whether additional HPCM DTCs are stored.
- Determine whether applicable Drive Motor Power Inverter Module calibration programming is required.
13. Possible repair or resolution
- For the defined bulletin scenario, reprogram the Drive Motor Power Inverter Module to the latest calibrations available.
- Whether any component replacement is required is not established by verified evidence for P0AC4 alone.
14. Affected vehicles
- Chevrolet Volt · 2016–2018 · US
- Chevrolet Volt · 2016–2017 · US
15. Related TSBs / service bulletins
- GM bulletin 16-NA-400, published December 8, 2016: describes the P0AC4 ECM/MIL request within a specified P0B01, P0B04, or P0807 freeze-frame scenario and directs Drive Motor Power Inverter Module reprogramming when all criteria apply. Source: https://static.nhtsa.gov/odi/tsbs/2016/MC-10111768-9999.pdf
- GM bulletin 18NA016, version 2, published March 6, 2019: the supplied evidence states that DTC P0AC4 was removed from the bulletin subject. Source: https://static.nhtsa.gov/odi/tsbs/2019/MC-10158809-9999.pdf
16. Recall information
- No recall information is established by the supplied verified evidence.
17. Official manufacturer information
Official NHTSA-hosted manufacturer communications are provided in the TSB/service bulletin section. Applicability supplied for this diagnostic is Chevrolet Volt, model years 2016–2018, US. The overlapping 2016–2017 and 2016–2018 applicability records do not establish more specific trim, build-date, or VIN applicability.
19. Frequently asked questions
What does P0AC4 mean on a Chevrolet Volt?
In the supplied GM bulletin evidence, P0AC4 is stored in the ECM and requests MIL illumination within a specific diagnostic scenario involving P0B01, P0B04, or P0807. The evidence does not establish a standalone meaning beyond that context.
Can P0AC4 be related to loss of propulsion?
GM bulletin 16-NA-400 states that vehicles may have loss of propulsion with P0B01, P0B04, or P0807 set. It also states that P0AC4 is stored in the ECM in that scenario. The evidence does not establish that P0AC4 alone causes or predicts loss of propulsion.
What is the documented repair?
When all freeze-frame criteria in GM bulletin 16-NA-400 apply, the documented action is to reprogram the Drive Motor Power Inverter Module to the latest available calibrations.
Does P0AC4 mean the inverter must be replaced?
Not yet established by verified evidence. The supplied bulletin directs reprogramming under specified conditions; it does not establish inverter replacement for P0AC4 alone.