Chevrolet P0421
The technician should follow SI diagnostics. If no cause for the concern is found or during diagnosis a
Quick answer
For the listed Chevrolet applications, P0421 appears in an official GM/NHTSA communication as one of many possible DTCs that may be present with an illuminated MIL and, intermittently, reduced engine power. The communication states that a charge-air-cooler/induction-system leak may be a cause of the concern and directs technicians to follow SI diagnostics. A P0421-specific meaning is not established by the supplied verified evidence.
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 P0421 mean?
For the listed Chevrolet applications, P0421 appears in an official GM/NHTSA communication as one of many possible DTCs that may be present with an illuminated MIL and, intermittently, reduced engine power. The communication states that a charge-air-cooler/induction-system leak may be a cause of the concern and directs technicians to follow SI diagnostics. A P0421-specific meaning is not established by the supplied verified evidence.
2. Technical explanation
The supplied official manufacturer communication, PIP5684C, lists P0421 among numerous current or history DTCs that can occur in the described condition. Its stated possible cause is a leak in the charge air cooler / induction systems. Its correction instruction is to follow SI diagnostics; the supplied excerpt ends mid-sentence, so no further procedure or repair direction is established here.
3. What system is affected?
Charge air cooler / induction systems are identified in the verified communication as a possible area of concern. A P0421-specific affected system is not yet established by verified evidence.
4. How serious is this code?
Unknown. The supplied diagnostic record marks severity as unknown.
5. Symptoms you may notice
- MIL illuminated.
- Intermittent reduced engine power may be commented on by the customer.
6. Possible causes
- A leak in the charge air cooler / induction systems may cause the concern described in the official communication.
- Any P0421-specific cause beyond that statement is 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. Because reduced engine power may occur, arrange professional diagnosis rather than relying on this page to determine driving safety.
8. Can I charge the vehicle?
Unknown. The supplied diagnostic record marks safe-to-charge status as unknown.
9. What you can safely do
- Follow the vehicle's service information (SI) diagnostic process through a qualified technician.
- Record whether the MIL is illuminated and whether reduced engine power occurs intermittently.
- Do not perform high-voltage system repairs based on this information.
10. Step-by-step troubleshooting
- A qualified technician should follow SI diagnostics, as directed by the official manufacturer communication.
- The verified communication identifies inspection/diagnosis of a possible charge-air-cooler or induction-system leak as relevant to the described concern.
- No additional diagnostic steps are established by the supplied evidence.
11. When to contact service
Professional service is appropriate because the official communication directs technicians to follow SI diagnostics and reduced engine power may be present. The supplied data does not establish urgency or an exact repair.
12. What the service center may check
- Follow Chevrolet/GM SI diagnostics for the reported condition and stored DTCs.
- Evaluate for a possible leak in the charge air cooler / induction systems, consistent with PIP5684C.
- Determine whether P0421 is current or history and assess it with any accompanying DTCs under SI diagnostics.
13. Possible repair or resolution
- No specific repair is established by the supplied verified evidence.
- The official communication directs technicians to follow SI diagnostics; repair depends on the cause found during that process.
14. Affected vehicles
- Chevrolet Bolt EV · 2011–2018 · US
- Chevrolet Spark · 2011–2018 · US
- Chevrolet Volt · 2011–2018 · US
15. Related TSBs / service bulletins
- NHTSA Manufacturer Communication PDF 10182564, GM PIP5684C, published October 22, 2020. It lists P0421 among possible history or current DTCs associated with an illuminated MIL and possible intermittent reduced engine power. It states that a charge-air-cooler/induction-system leak may be the cause and directs technicians to follow SI diagnostics.
- Source: https://static.nhtsa.gov/odi/tsbs/2020/MC-10182564-9999.pdf
16. Recall information
- No recall information is supplied or established by the verified evidence.
17. Official manufacturer information
Verified source: NHTSA-hosted manufacturer communication PIP5684C, NHTSA Manufacturer Communication PDF 10182564, published 2020-10-22: https://static.nhtsa.gov/odi/tsbs/2020/MC-10182564-9999.pdf
19. Frequently asked questions
What does P0421 mean on these Chevrolet vehicles?
The supplied diagnostic record uses truncated wording and does not establish a complete P0421-specific definition. The verified manufacturer communication lists P0421 as one of many possible DTCs in the described condition.
Can a charge-air or induction leak be related to P0421?
The verified communication says a leak in the charge air cooler / induction systems may cause the described concern, while listing P0421 among possible accompanying DTCs. It does not establish that every P0421 is caused by such a leak.
Can I drive with P0421?
Not yet established by verified evidence. Safe-to-drive status is marked unknown, and the communication notes that reduced engine power may occur intermittently.
What repair fixes P0421?
Not yet established by verified evidence. The official communication directs a technician to follow SI diagnostics; the needed repair depends on the diagnosed cause.