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Hyundai C1259

> if present with these DTCs, replace column and housing assembly. If DTC returns, replace MDPS ECU. C1687 CAN time out VSM C1688 VSM signal error  If DTC returns and MDPS is inop

DriveNot yet established by verified evidence.
ChargeNot yet established by verified evidence.
ServiceService evaluation is appropriate. Hyundai’s published process requires diagnosis of wiring, connectors, DTC status, and any accompanying codes before selecting a repair.
Confidence95%

Quick answer

For the listed Hyundai applications, C1259 is identified in Hyundai service communications as a steering angle sensor signal error. Hyundai directs technicians to inspect C-MDPS/TAS wiring and connectors, erase and recheck DTCs, and follow the applicable MDPS repair flowchart. If C1259 is active or stored in history in the specified Sonata bulletin, replace the torque sensor cable.

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 C1259 mean?

For the listed Hyundai applications, C1259 is identified in Hyundai service communications as a steering angle sensor signal error. Hyundai directs technicians to inspect C-MDPS/TAS wiring and connectors, erase and recheck DTCs, and follow the applicable MDPS repair flowchart. If C1259 is active or stored in history in the specified Sonata bulletin, replace the torque sensor cable.

2. Technical explanation

Verified Hyundai/NHTSA service-bulletin evidence describes C1259 as a steering angle sensor signal error. The published diagnostic guidance includes checking C-MDPS connectors and wiring, checking connectors for poor connection, corrosion, damage, or deformation, erasing DTCs, and rechecking. One bulletin specifically directs inspection of Torque Angle Sensor (TAS) wiring for damage, terminal push-back, or improper connection. The exact repair path depends on the vehicle configuration, accompanying DTCs, and whether the code returns after the prescribed checks.

3. What system is affected?

Motor-Driven Power Steering (MDPS/C-MDPS), including steering-angle/torque-angle-sensor wiring and related controller communications.

4. How serious is this code?

Not yet established by verified evidence.

5. Symptoms you may notice

  • A warning lamp illuminated with DTC(s) present is referenced by the Hyundai repair-flowchart bulletin.
  • MDPS may be inoperable if the DTC returns, as described in the C1687/C1688 repair guidance.

6. Possible causes

  • Damage, push-back, or improper connection in Torque Angle Sensor wiring.
  • Poor connector connection.
  • Connector corrosion.
  • Connector damage or deformation.
  • Wiring issues, where the relevant MDPS guidance directs further investigation.

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

  • Arrange diagnosis by a qualified Hyundai service technician using the applicable Hyundai diagnostic procedure.
  • Provide all active and history DTCs, since the published repair flow depends on accompanying codes and whether DTCs return.

10. Step-by-step troubleshooting

  1. Check C-MDPS connectors and wiring.
  2. Check applicable HECU, C-MDPS, and EMS wiring and connectors for poor connection, corrosion, damage, or deformation.
  3. For C1259 and/or C1290, inspect TAS wiring for damage, terminal push-back, or improper connection.
  4. Erase DTCs and recheck, as directed by the Hyundai bulletins.
  5. Use the applicable Hyundai DTC Diagnostic Guide and MDPS repair flowchart.

11. When to contact service

Service evaluation is appropriate. Hyundai’s published process requires diagnosis of wiring, connectors, DTC status, and any accompanying codes before selecting a repair.

12. What the service center may check

  • Read active and history DTCs.
  • Inspect C-MDPS connectors and wiring.
  • Inspect relevant HECU/C-MDPS/EMS connectors and wiring where applicable.
  • Inspect TAS wiring condition and connector terminal retention where applicable.
  • Check MDPS power connector and fuse, MDPS ground line, MDPS ECU/VSM CAN line, and GDS communication status when following the C1623/C1687/C1688 flow.
  • Erase DTCs and determine whether they return.

13. Possible repair or resolution

  • For the specified 2015–2017 Sonata bulletin, if C1259 or C1290 is found in history or active, replace the torque sensor cable.
  • If a TAS harness issue is found in the applicable C-MDPS procedure, replace the full C-MDPS as directed by that bulletin.
  • Where C1259 is present with the relevant communication-code flow, Hyundai directs replacement of the column and housing assembly; if the DTC returns, replace the MDPS ECU or Power Pack Assembly as applicable.
  • For C1687/C1688 guidance, if the DTC returns and MDPS is inoperable, replace the MDPS ECU or Power Pack Assembly as applicable; if MDPS operates normally, continue investigating wiring issues.

14. Affected vehicles

15. Related TSBs / service bulletins

  • Hyundai TSB 22-ST-001H, published January 6, 2022: 2015–2017 Sonata (LFA, LF HEV/PHEV) R-MDPS diagnostic trouble code repair flowchart; references C1259/C1290 torque sensor cable replacement criteria. NHTSA communication 10207815.
  • Hyundai TSB 20-ST-001H-2, published September 9, 2020: C-MDPS component replacement information and TAS wiring inspection for C1259 and/or C1290. NHTSA communication 10180981.
  • Hyundai TSB 20-ST-001H-1, published August 10, 2020: C-MDPS component replacement information and TAS wiring inspection for C1259 and/or C1290. NHTSA communication 10179244.
  • Hyundai TSB 20-ST-001H, published January 3, 2020: MDPS DTC repair guidance including C1259 with C1623/C1687/C1688. NHTSA communication 10170896.
  • Hyundai TSB 19-ST-001H, published April 22, 2019: MDPS DTC repair guidance including C1259 with C1623/C1687/C1688. NHTSA communication 10160106.

16. Recall information

  • Not yet established by verified evidence.

17. Official manufacturer information

Verified official manufacturer communications are available through NHTSA: https://static.nhtsa.gov/odi/tsbs/2022/MC-10207815-0001.pdf ; https://static.nhtsa.gov/odi/tsbs/2020/MC-10180981-0001.pdf ; https://static.nhtsa.gov/odi/tsbs/2020/MC-10179244-0001.pdf ; https://static.nhtsa.gov/odi/tsbs/2020/MC-10170896-0001.pdf ; https://static.nhtsa.gov/odi/tsbs/2019/MC-10160106-9999.pdf

19. Frequently asked questions

What does Hyundai C1259 mean?

Verified Hyundai bulletin evidence identifies C1259 as a steering angle sensor signal error.

What should be inspected for C1259?

Hyundai guidance calls for inspection of C-MDPS/TAS wiring and connectors, including poor connections, corrosion, damage, deformation, terminal push-back, and improper connection where applicable.

Does C1259 always require MDPS ECU replacement?

No. The published repair path varies by vehicle configuration, accompanying DTCs, inspection results, and whether the DTC returns. Hyundai guidance includes wiring inspection and, in specified conditions, torque sensor cable, column and housing assembly, C-MDPS, MDPS ECU, or Power Pack Assembly replacement.

Which vehicles are listed in the supplied applicability data?

US-market Hyundai Kona model years 2016–2021 and Hyundai Sonata model years 2016–2021 are listed. Bulletin-specific applicability must be confirmed before applying a particular repair procedure.

20. Sources & verification

Verified
Hyundai C1259: > if present with these DTCs, replace column and… | EV Diagnostics