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Kia C1688

MDPS MOTOR, ECU AND/OR STEERING COLUMN HOUSING Page 4 of 5 TSB: CHA084 (Rev 3) Multiple Models November 2018 SUBJECT: Replacement Procedure for MDPS Motor: 1. Replace the

DriveNot yet established by verified evidence. The supplied bulletin identifies a condition in which MDPS is inoperable but does not provide a driving-safety determination.
ChargeNot yet established by verified evidence. The supplied evidence does not address charging.
ServiceContact a Kia dealer or qualified service facility for diagnosis under the latest applicable Kia service information, particularly if C1688 returns or MDPS is inoperable.
Confidence95%

Quick answer

For Kia vehicles covered by TSB CHA084, DTC C1688 is identified as “VSM Signal Error.” If the DTC returns and MDPS is inoperable, the bulletin directs replacement of the MDPS ECU. If the DTC returns while MDPS operation is normal, the bulletin directs continued investigation of wiring issues.

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 C1688 mean?

For Kia vehicles covered by TSB CHA084, DTC C1688 is identified as “VSM Signal Error.” If the DTC returns and MDPS is inoperable, the bulletin directs replacement of the MDPS ECU. If the DTC returns while MDPS operation is normal, the bulletin directs continued investigation of wiring issues.

2. Technical explanation

Verified Kia TSB CHA084 revisions 3 through 8 list C1688 as “VSM Signal Error.” MDPS refers to the motor-driven power steering system, and VSM is referenced by the DTC description. The supplied evidence does not establish a more specific component-level fault from C1688 alone.

3. What system is affected?

Motor-Driven Power Steering (MDPS), including the MDPS ECU and associated wiring; the DTC description references a VSM signal.

4. How serious is this code?

Not yet established by verified evidence. The bulletin distinguishes between an inoperable MDPS condition and normal MDPS operation.

5. Symptoms you may notice

  • MDPS may be inoperable, as described in the TSB decision path.
  • MDPS operation may remain normal, as described in the alternative TSB decision path.

6. Possible causes

  • A condition requiring MDPS ECU replacement is indicated by the bulletin when C1688 returns and MDPS is inoperable.
  • Wiring issues require further investigation when C1688 returns and MDPS operation is normal.
  • Not yet established by verified evidence whether any particular wire, connector, VSM component, or other component is the cause in an individual vehicle.

7. Can I still drive the vehicle?

Not yet established by verified evidence. The supplied bulletin identifies a condition in which MDPS is inoperable but does not provide a driving-safety determination.

8. Can I charge the vehicle?

Not yet established by verified evidence. The supplied evidence does not address charging.

9. What you can safely do

  • Have the DTC evaluated using the applicable Kia service information.
  • If C1688 returns, have a qualified service facility determine whether MDPS is inoperable or operating normally.
  • Use the latest Kia service information; the bulletin states that printed copies are for reference and information may be updated.

10. Step-by-step troubleshooting

  1. Confirm whether C1688 returns after diagnosis.
  2. Determine whether MDPS is inoperable or operating normally.
  3. If C1688 returns with normal MDPS operation, continue investigation into wiring issues, as directed by TSB CHA084.

11. When to contact service

Contact a Kia dealer or qualified service facility for diagnosis under the latest applicable Kia service information, particularly if C1688 returns or MDPS is inoperable.

12. What the service center may check

  • Confirm recurrence of DTC C1688.
  • Assess MDPS operating status.
  • Investigate wiring issues if C1688 returns and MDPS operation is normal.

13. Possible repair or resolution

  • If C1688 returns and MDPS is inoperable, TSB CHA084 directs replacement of the MDPS ECU.
  • If C1688 returns and MDPS operation is normal, TSB CHA084 directs continued investigation into wiring issues.

14. Affected vehicles

15. Related TSBs / service bulletins

  • Kia TSB CHA084, “Replacement of C-MDPS Motor, ECU and/or Steering Column Housing,” revisions 3 through 8, is documented in NHTSA manufacturer communications published from October 2019 through October 2021. Its C1688 guidance states: replace the MDPS ECU if the DTC returns and MDPS is inoperable; continue investigating wiring issues if the DTC returns and MDPS operation is normal.

16. Recall information

  • Not yet established by verified evidence. The supplied records are manufacturer communications/TSBs, not recall records.

17. Official manufacturer information

Official NHTSA-hosted Kia TSB CHA084 Rev. 8: https://static.nhtsa.gov/odi/tsbs/2021/MC-10202226-0001.pdf

19. Frequently asked questions

What does Kia DTC C1688 mean?

The verified TSB identifies C1688 as “VSM Signal Error.”

What does the TSB say to do if C1688 returns and power steering is inoperable?

TSB CHA084 directs replacement of the MDPS ECU.

What does the TSB say if C1688 returns but MDPS operates normally?

TSB CHA084 directs continued investigation into wiring issues.

Does C1688 prove that the MDPS ECU has failed?

No. The verified bulletin only directs MDPS ECU replacement when the DTC returns and MDPS is inoperable.

20. Sources & verification

Verified
Kia C1688: MDPS MOTOR, ECU AND/OR STEERING COLUMN HOUSING Page 4 of 5… | EV Diagnostics