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2017 Kia Optima - Transmission in Limp Mode, P0700 & P0705 Codes

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Nicole W. · rep 0 · May 22, 3:05 AM · 1 replies · solved · Question

Vehicle: 2017 Kia Optima EX 2.4L

My 2017 Kia Optima EX (2.4L) suddenly went into limp mode yesterday. The Check Engine Light came on, and the car feels sluggish, like it's stuck in a higher gear. I pulled the codes, and I'm getting P0700 (Transmission Control System Malfunction) and P0705 (Transmission Range Sensor Circuit Malfunction).

I've read that P0700 is a generic code that points to a transmission issue, and P0705 specifically points to the Transmission Range Sensor (TRS), also known as the neutral safety switch. Could a bad TRS really cause limp mode?

Has anyone dealt with this on their Optima? Is this a DIY fix, or am I looking at a trip to the dealership? Any advice on troubleshooting would be great.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:05 AM

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ClearTheCode admin answer:

Your 2017 Kia Optima entering limp mode with P0700 and P0705 codes strongly points to an issue with the Transmission Range Sensor (TRS), also commonly known as the neutral safety switch. The P0700 code is a general indicator from the Engine Control Module (ECM) that the Transmission Control Module (TCM) has detected a fault, and the P0705 code specifies that the fault is with the TRS circuit.

Here's what you need to know and how to approach it:

  1. Understanding the TRS: The Transmission Range Sensor tells the TCM (and ECM) what gear the transmission is in (Park, Reverse, Neutral, Drive). If this sensor provides incorrect or no data, the TCM can't properly manage gear shifts, leading to limp mode to protect the transmission.
  2. Symptoms: Limp mode, difficulty shifting, being stuck in a single gear (often 3rd or 4th), and the inability to start the car in Park or Neutral are all common symptoms of a faulty TRS.
  3. Common Causes:
    • Faulty Sensor: The sensor itself can fail electronically or mechanically.
    • Wiring Issues: Damaged, corroded, or loose wiring/connectors to the TRS can interrupt the signal.
    • Adjustment: Sometimes, the sensor might just be out of adjustment, though this is less common for sudden onset issues.

Diagnostic Steps & Potential Fixes:

  • Visual Inspection: Check the wiring harness and connector leading to the TRS for any signs of damage, corrosion, or looseness. Ensure it's securely plugged in.
  • Sensor Location: The TRS is typically located on the outside of the transmission, where the shift linkage connects. It's usually accessible.
  • Replacement: Replacing the TRS is often a straightforward repair for someone with basic mechanical skills. It usually involves disconnecting the battery, removing the shift cable, unbolting the old sensor, installing the new one, and reconnecting everything. Ensure the new sensor is properly aligned.

When to See a Shop:

  • If a visual inspection doesn't reveal any obvious wiring issues.
  • If you're not comfortable working on transmission components or electrical systems.
  • After replacing the TRS, if the codes persist or the vehicle remains in limp mode, there might be a deeper issue within the TCM or transmission itself, which requires professional diagnosis with specialized scan tools.
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