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Chevrolet P0420

The technician should follow SI diagnostics. If no cause for the concern is found or during diagnosis a leak che

DriveUnknown. The supplied diagnostic record marks safe-to-drive status as unknown.
ChargeUnknown. The supplied diagnostic record marks safe-to-charge status as unknown.
ServiceService evaluation is appropriate because the official Chevrolet communications direct technicians to follow SI diagnostics. The supplied record does not establish urgency, drivability, charging status, or a specific repair.
Confidence95%

Quick answer

For the supplied Chevrolet applicability, P0420 is listed in Chevrolet bulletin PIP5684/PIP5684A/B/C among possible history or current DTCs. The bulletin says to follow SI diagnostics; it identifies a possible charge-air-cooler/induction-system leak for the described concern, but the supplied evidence does not establish that this is the cause of P0420 in every vehicle.

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

Video guides

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DTC Chevrolet P0420 Short ExplanationMaxidot Chevrolet
Causes and Fixes Chevrolet P0420 Code: Catalyst System Low Efficiency Bank 1HVAC Mechanic

Videos are supporting material and never override OEM or regulator evidence.

1. What does P0420 mean?

For the supplied Chevrolet applicability, P0420 is listed in Chevrolet bulletin PIP5684/PIP5684A/B/C among possible history or current DTCs. The bulletin says to follow SI diagnostics; it identifies a possible charge-air-cooler/induction-system leak for the described concern, but the supplied evidence does not establish that this is the cause of P0420 in every vehicle.

2. Technical explanation

The supplied diagnostic record’s canonical instruction is: “The technician should follow SI diagnostics.” Official NHTSA-posted Chevrolet communications PIP5684, PIP5684A, PIP5684B, and PIP5684C list P0420 among many possible history or current DTCs. Those communications state that the described concern may be due to a leak in the charge air cooler/induction systems and direct the technician to follow SI diagnostics. The supplied evidence does not provide a complete code definition for P0420 or establish a single confirmed fault mechanism.

3. What system is affected?

Not yet established by verified evidence. The cited bulletin discusses the charge air cooler/induction systems as a possible source of the described concern.

4. How serious is this code?

Unknown. The supplied diagnostic record marks severity as unknown.

5. Symptoms you may notice

  • MIL illumination is described in the cited Chevrolet communications.
  • Intermittent reduced engine power is described as a possible customer comment in the cited Chevrolet communications.
  • The supplied evidence does not establish that either symptom will occur whenever P0420 is present.

6. Possible causes

  • A leak in the charge air cooler/induction systems may be a cause of the concern described in Chevrolet bulletin PIP5684 and its revisions.
  • The supplied evidence does not establish that an induction-system leak is the cause of P0420 on a particular vehicle.
  • Other causes are not yet established by verified evidence.

7. Can I still drive the vehicle?

Unknown. The supplied diagnostic record marks safe-to-drive status as unknown.

8. Can I charge the vehicle?

Unknown. The supplied diagnostic record marks safe-to-charge status as unknown.

9. What you can safely do

  • Arrange diagnosis using the applicable Chevrolet Service Information (SI) procedures.
  • Record whether the MIL is illuminated and whether reduced engine power occurs.
  • Do not assume that P0420 alone confirms the cause described in the bulletin.

10. Step-by-step troubleshooting

  1. Follow the applicable Chevrolet SI diagnostics, as directed by PIP5684/PIP5684A/PIP5684B/PIP5684C.
  2. If no cause is found during diagnosis, the supplied bulletin evidence indicates that a leak check is relevant; the exact procedure is not included in the supplied evidence.
  3. Do not perform high-voltage repair work based on this information.

11. When to contact service

Service evaluation is appropriate because the official Chevrolet communications direct technicians to follow SI diagnostics. The supplied record does not establish urgency, drivability, charging status, or a specific repair.

12. What the service center may check

  • Retrieve history and current DTCs as part of the applicable SI diagnostic process.
  • Follow Chevrolet SI diagnostics for the vehicle and concern.
  • Consider the bulletin’s identified possibility of a charge-air-cooler/induction-system leak when performing the applicable diagnostic process.

13. Possible repair or resolution

  • Not yet established by verified evidence. The supplied sources provide a diagnostic direction, not a confirmed repair for every P0420 occurrence.
  • Any repair should follow the result of the applicable Chevrolet SI diagnostic procedure.

14. Affected vehicles

15. Related TSBs / service bulletins

  • Chevrolet PIP5684, NHTSA Manufacturer Communication MC-10167455, published 2019-10-22: P0420 is listed among possible history or current DTCs; the communication identifies a possible charge-air-cooler/induction-system leak and directs technicians to follow SI diagnostics. https://static.nhtsa.gov/odi/tsbs/2019/MC-10167455-9999.pdf
  • Chevrolet PIP5684A, NHTSA Manufacturer Communication MC-10176300, published 2020-05-05: P0420 is listed among possible history or current DTCs; the communication identifies a possible charge-air-cooler/induction-system leak and directs technicians to follow SI diagnostics. https://static.nhtsa.gov/odi/tsbs/2020/MC-10176300-9999.pdf
  • Chevrolet PIP5684B, NHTSA Manufacturer Communication MC-10178370, published 2020-07-13: P0420 is listed among possible history or current DTCs; the communication identifies a possible charge-air-cooler/induction-system leak and directs technicians to follow SI diagnostics. https://static.nhtsa.gov/odi/tsbs/2020/MC-10178370-9999.pdf
  • Chevrolet PIP5684C, NHTSA Manufacturer Communication MC-10182564, published 2020-10-22: P0420 is listed among possible history or current DTCs; the communication identifies a possible charge-air-cooler/induction-system leak and directs technicians to follow SI diagnostics. https://static.nhtsa.gov/odi/tsbs/2020/MC-10182564-9999.pdf

16. Recall information

  • Not yet established by verified evidence.

17. Official manufacturer information

Verified source: NHTSA-posted Chevrolet manufacturer communications PIP5684 through PIP5684C. The supplied applicability records identify Chevrolet Bolt EV, Spark, and Volt, model years 2011–2018, US region. The bulletin applicability itself is not fully reproduced in the supplied evidence; confirm bulletin applicability by VIN and vehicle configuration through Chevrolet service information.

19. Frequently asked questions

Does P0420 confirm a charge-air-cooler or induction-system leak?

No. The cited Chevrolet communications say such a leak may be a cause of the described concern; they do not establish it as the confirmed cause of every P0420 occurrence.

What does Chevrolet direct the technician to do?

Follow SI diagnostics. The supplied evidence also indicates that a leak check is relevant if no cause is found during diagnosis, but it does not include the complete procedure.

Can I drive or charge the vehicle?

Not yet established by verified evidence. The supplied diagnostic record lists both safe-to-drive and safe-to-charge status as unknown.

Is P0420 applicable to Chevrolet Bolt EV, Spark, and Volt?

The supplied applicability data lists US Chevrolet Bolt EV, Spark, and Volt model years 2011–2018. Confirm applicability for the individual vehicle through Chevrolet service information.

20. Sources & verification

ReferenceVerified
Chevrolet P0420: The technician should follow SI diagnostics. If no… | EV Diagnostics