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Scion P1604

up on piston head. Follow the Repair Procedure in this Service Bulletin to addr

DriveUnknown. The supplied diagnostic record lists safe-to-drive status as unknown.
ChargeUnknown. The supplied diagnostic record lists safe-to-charge status as unknown.
ServiceService is recommended because the official manufacturer communication directs technicians to follow its repair procedure. The supplied record does not establish urgency or drivability restrictions.
Confidence95%

Quick answer

For a 2013 Scion iQ in the US, DTC P1604 is covered by NHTSA-posted manufacturer communication S-SB-0008-16. The bulletin associates it with rough idle, a momentary idle-speed drop, and/or MIL illumination. Its evidence summary states excessive carbon build-up on the piston head may be involved.

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

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Need to Know the Details!!! Scion xD 1.8 P0420 P1604.Rainman Ray's Repairs

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1. What does P1604 mean?

For a 2013 Scion iQ in the US, DTC P1604 is covered by NHTSA-posted manufacturer communication S-SB-0008-16. The bulletin associates it with rough idle, a momentary idle-speed drop, and/or MIL illumination. Its evidence summary states excessive carbon build-up on the piston head may be involved.

2. Technical explanation

The supplied verified evidence identifies P1604 in an official Scion/Toyota manufacturer service bulletin, S-SB-0008-16. The bulletin summary lists P1604 together with P1603 and/or P1605 and directs technicians to follow its repair procedure. The supplied excerpt does not provide the complete diagnostic or repair procedure.

3. What system is affected?

Not yet established by verified evidence. The bulletin evidence refers to carbon build-up on the piston head and idle-related behavior.

4. How serious is this code?

Unknown. The supplied diagnostic record lists severity as unknown.

5. Symptoms you may notice

  • Rough idle condition.
  • Idle speed momentarily drops at idle.
  • MIL illumination with P1604, potentially with P1603 and/or P1605.

6. Possible causes

  • Excessive carbon build-up on the piston head may cause the listed rough-idle, idle-drop, and MIL/DTC conditions, according to S-SB-0008-16.

7. Can I still drive the vehicle?

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

8. Can I charge the vehicle?

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

9. What you can safely do

  • Have the vehicle evaluated using the repair procedure in Scion/Toyota service bulletin S-SB-0008-16.
  • Record whether rough idle, a momentary idle-speed drop, or MIL illumination is present.

10. Step-by-step troubleshooting

  1. Confirm the stored DTC is P1604.
  2. Check whether P1603 and/or P1605 are also stored.
  3. Refer to the repair procedure in S-SB-0008-16. The supplied evidence does not include the procedure details.

11. When to contact service

Service is recommended because the official manufacturer communication directs technicians to follow its repair procedure. The supplied record does not establish urgency or drivability restrictions.

12. What the service center may check

  • Confirm P1604 and any accompanying P1603 or P1605 DTCs.
  • Evaluate the rough-idle or momentary idle-speed-drop concern in accordance with S-SB-0008-16.
  • Follow the bulletin repair procedure; its specific steps are not contained in the supplied evidence.

13. Possible repair or resolution

  • The verified bulletin directs use of its Repair Procedure to address the condition. The exact repair is not yet established by the supplied evidence.

14. Affected vehicles

15. Related TSBs / service bulletins

  • S-SB-0008-16, NHTSA Manufacturer Communication 10132874, published October 20, 2016. It applies in the supplied applicability data to the 2013 Scion iQ, US. The bulletin summary links rough idle, momentary idle-speed drop, and/or MIL illumination with P1603, P1604, and/or P1605, and states excessive carbon build-up on the piston head may be involved.

16. Recall information

  • Not yet established by verified evidence.

17. Official manufacturer information

Official source: NHTSA Manufacturer Communication 10132874, Scion/Toyota service bulletin S-SB-0008-16: https://static.nhtsa.gov/odi/ffdd/tsbs/TSBS_RECEIVED_2015-2019.zip#nhtsa_id=10132874

19. Frequently asked questions

What does P1604 mean on a 2013 Scion iQ?

The supplied verified record associates P1604 with Scion bulletin S-SB-0008-16. The evidence summary describes rough idle, a momentary idle-speed drop, and/or MIL illumination, and says excessive carbon build-up on the piston head may be involved.

Which vehicles are covered by the supplied bulletin evidence?

The supplied applicability data identifies the 2013 Scion iQ in the US.

Can P1604 occur with other codes?

Yes. The bulletin summary lists P1603, P1604, and/or P1605.

Is it safe to drive or charge with P1604?

Not yet established by verified evidence. Both safe-to-drive and safe-to-charge statuses are listed as unknown in the supplied diagnostic record.

20. Sources & verification

Verified
Scion P1604: up on piston head. Follow the Repair Procedure in this… | EV Diagnostics