Scion P1605
up on piston head. Follow the Repair Procedure in this Service Bulletin to address this cond
Quick answer
For a 2013 Scion iQ in the US, DTC P1605 is covered by NHTSA manufacturer communication S-SB-0008-16 when it occurs with a rough idle, a momentary idle-speed drop, and/or a MIL. The bulletin states that P1603, P1604, and/or P1605 may be caused by excessive carbon build-up on the piston head and directs technicians to its repair procedure.
This page separates verified manufacturer/regulator evidence from supporting material. Unsupported causes, repairs or safety conclusions are not guessed.
Watch Videos
Relevant videos play here without leaving this diagnostic page.
No sufficiently relevant embeddable video has been accepted for this diagnostic yet.
Videos are supporting material and never override OEM or regulator evidence.
1. What does P1605 mean?
For a 2013 Scion iQ in the US, DTC P1605 is covered by NHTSA manufacturer communication S-SB-0008-16 when it occurs with a rough idle, a momentary idle-speed drop, and/or a MIL. The bulletin states that P1603, P1604, and/or P1605 may be caused by excessive carbon build-up on the piston head and directs technicians to its repair procedure.
2. Technical explanation
Verified evidence links P1605 to an engine-idle condition described in Scion service bulletin S-SB-0008-16. The bulletin identifies excessive carbon build-up on the piston head as a possible cause of the listed condition; it does not establish that carbon build-up is the cause of every P1605 occurrence.
3. What system is affected?
Engine/idle operation is indicated by the verified bulletin. A more specific system designation is 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
- Rough idle condition.
- Idle speed momentarily drops at idle.
- MIL ON with P1603, P1604, and/or P1605.
6. Possible causes
- Excessive carbon build-up on the piston head may cause the condition described in S-SB-0008-16.
7. Can I still drive the vehicle?
Not yet established by verified evidence.
8. Can I charge the vehicle?
Not yet established by verified evidence.
9. What you can safely do
- Have the vehicle evaluated by a qualified service provider using the repair procedure in S-SB-0008-16.
- Record whether the MIL is on and whether rough idle or a momentary idle-speed drop occurs.
10. Step-by-step troubleshooting
- Confirm the stored DTCs, including whether P1603 or P1604 is also present.
- Confirm whether the rough-idle and idle-speed-drop condition described in S-SB-0008-16 is present.
- Refer to the repair procedure in S-SB-0008-16.
11. When to contact service
Service is recommended when the documented idle symptoms and/or MIL with P1605 are present. The supplied evidence does not state an urgency classification.
12. What the service center may check
- Check for P1603, P1604, and/or P1605.
- Evaluate for the rough-idle condition and momentary idle-speed drop described in S-SB-0008-16.
- Follow the service bulletin repair procedure for the documented condition.
13. Possible repair or resolution
- The verified bulletin directs use of its Repair Procedure to address the condition. Specific repair steps and parts are not included in the supplied evidence.
14. Affected vehicles
- Scion iQ · 2013 · US
15. Related TSBs / service bulletins
- S-SB-0008-16, published October 20, 2016, NHTSA Manufacturer Communication 10132874. It applies in the supplied data to the 2013 Scion iQ in the US and addresses rough idle, momentary idle-speed drop, and MIL illumination with P1603, P1604, and/or P1605.
16. Recall information
- No recall information was supplied or established by verified evidence.
17. Official manufacturer information
Official source: NHTSA Manufacturer Communication 10132874, Scion 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 P1605 mean for a 2013 Scion iQ?
In the supplied official bulletin, P1605 is one of the DTCs that may appear with rough idle, a momentary idle-speed drop, and MIL illumination. The bulletin states that excessive carbon build-up on the piston head may cause this condition.
Which vehicles are supported by the supplied evidence?
The supplied applicability evidence identifies the 2013 Scion iQ for the US region.
Is P1605 definitely caused by piston-head carbon build-up?
No. The bulletin says excessive carbon build-up may cause the documented condition; it does not establish this cause for every P1605.
Can I drive or charge with P1605?
Driving and charging guidance are not yet established by verified evidence.