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Subaru P1378

“Pre-Ignition Detected” – 2019MY Ascent ................................................................................07/18 2019MY Ascen

DriveUnknown. The supplied verified evidence does not state whether the vehicle can be driven with P1378.
ChargeUnknown. The supplied verified evidence does not state whether charging is permitted or restricted with P1378.
ServiceService need is not established by the supplied evidence. If P1378 is present, consult a Subaru retailer or qualified service facility for diagnosis using applicable Subaru information.
Confidence95%

Quick answer

P1378 is identified in the verified Subaru/NHTSA material as “Pre-Ignition Detected” for the 2019 model-year Subaru Ascent. The supplied evidence does not establish a diagnosis, repair, driving recommendation, or charging recommendation.

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 P1378 mean?

P1378 is identified in the verified Subaru/NHTSA material as “Pre-Ignition Detected” for the 2019 model-year Subaru Ascent. The supplied evidence does not establish a diagnosis, repair, driving recommendation, or charging recommendation.

2. Technical explanation

Verified NHTSA-posted Subaru manufacturer communications list DTC P1378 as “Pre-Ignition Detected” and associate the entry with the 2019MY Ascent. The supplied excerpt does not include diagnostic criteria, affected components, fault conditions, or repair procedures.

3. What system is affected?

Not yet established by verified evidence.

4. How serious is this code?

Unknown. The supplied 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. The supplied verified evidence does not state whether the vehicle can be driven with P1378.

8. Can I charge the vehicle?

Unknown. The supplied verified evidence does not state whether charging is permitted or restricted with P1378.

9. What you can safely do

  • Record the stored code as P1378.
  • Have the vehicle assessed using applicable Subaru service information.
  • Do not perform high-voltage repair procedures based on this information.

10. Step-by-step troubleshooting

  1. No evidence-backed troubleshooting sequence is provided in the supplied records.
  2. A qualified service facility should use applicable Subaru diagnostic information to determine the fault condition.

11. When to contact service

Service need is not established by the supplied evidence. If P1378 is present, consult a Subaru retailer or qualified service facility for diagnosis using applicable Subaru information.

12. What the service center may check

  • Not yet established by verified evidence.

13. Possible repair or resolution

  • Not yet established by verified evidence.

14. Affected vehicles

15. Related TSBs / service bulletins

  • NHTSA Manufacturer Communication PDF 11036794, published August 5, 2026: its supplied summary lists “DTC P1378 – ‘Pre-Ignition Detected’ – 2019MY Ascent.”
  • NHTSA Manufacturer Communication PDF 11024859, published October 28, 2025: its supplied summary lists “DTC P1378 – ‘Pre-Ignition Detected’ – 2019MY Ascent.”
  • NHTSA Manufacturer Communication PDF 11024863, published October 28, 2025: its supplied summary lists “DTC P1378 – ‘Pre-Ignition Detected’ – 2019MY Ascent.”

16. Recall information

  • Not yet established by verified evidence.

17. Official manufacturer information

Official NHTSA-hosted manufacturer communication evidence: https://static.nhtsa.gov/odi/tsbs/2026/MC-11036794-0001.pdf

19. Frequently asked questions

What does Subaru code P1378 mean?

The verified evidence identifies P1378 as “Pre-Ignition Detected” for the 2019 model-year Subaru Ascent.

Does P1378 apply to an EV or charging system?

Not yet established by verified evidence.

Can I drive with P1378?

Not yet established by verified evidence.

What repair fixes P1378?

Not yet established by verified evidence.

20. Sources & verification

Verified
Subaru P1378: “Pre-Ignition Detected” – 2019MY Ascent… | EV Diagnostics