P1603: owner reports and bulletins
Got P1603 on your scanner? Tell the mechanic your year, make, model and any symptoms and you'll get the likely cause and what to check first. Ask about this code.
What owners report to NHTSA
14 complaints filed with NHTSA mention P1603, 14 of them since 2015, across 8 different models. The component owners most often filed it under: engine.
Most-reported models
| Vehicle | Complaints | Model years reported |
|---|---|---|
| TOYOTA RAV4 | 5 | 2012, 2018 |
Manufacturer service bulletins that name P1603
9 technical service bulletins and manufacturer communications filed with NHTSA mention P1603, from 3 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- HYUNDAI VENUE (2020, 2021, 2026), bulletin 10233540: Certain 2020-22MY Venue (QX) vehicles may experience a check engine light or malfunction indicator light due to Diagnostic Trouble Codes (DTC) listed below. Perform the TCU update, and, if necessary, replace the IVT (Int…
- HYUNDAI ACCENT (2020, 2021), bulletin 10251288: Certain 2020-2021MY Accent (HC) vehicles may experience an illuminated warning light due to the following Diagnostic Trouble Codes (DTC) listed below: TCU DTC Codes: P0730, P0731, P0741, P0867, P1603 Follow the procedure…
- HYUNDAI ELANTRA (2020), bulletin 10177135: Certain vehicles may experience an illuminated warning light due to Diagnostic Trouble Codes (DTC). Perform the ECU and TCU update, and, if necessary, replace the IVT (Intelligent Variable Transmission) to resolve this c…
- TOYOTA HIGHLANDER (2014, 2015, 2016, 2017), bulletin 10162756: TSB: Some 2014 ? 2018 model year Highlander and Highlander Hybrid vehicles may exhibit one or more of the following conditions. ? Various drivability concerns ? Low or no fuel pressure ? Diagnostic Trouble Codes (DTCs) (…
- SCION IQ (2012, 2013), bulletin 10132874: TSB: Some 2012 ? 2013 model year iQ vehicles may exhibit one or more of the following conditions: * Rough idle condition. * Idle speed momentarily drops at idle. * MIL ?ON? with one or more of the following DTCs: P1603, …
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.