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Engine-Codes – GMC – P0708 2015 GMC Sierra

P0708 2015 GMC Sierra Code - Transmission Range Switch Circuit High Voltage

Quick Answer

The P0708 code for a 2015 GMC Sierra indicates a Transmission Range Switch Circuit High Voltage issue. Common causes include Faulty transmission range switch, Wiring issues or short circuits in the transmission range switch circuit, Corrosion or poor connections in the electrical system. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0708 2015 GMC Sierra indicates Transmission Range Switch Circuit High Voltage.
Common causes
Common causes include Faulty transmission range switch, Wiring issues or short circuits in the transmission range switch circuit, Corrosion or poor connections in the electrical system.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Aug 19, 2024
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Code P0708 2015 GMC Sierra Description

The P0708 code for a 2015 GMC Sierra indicates a Transmission Range Switch Circuit High Voltage issue. This means that the powertrain control module (PCM) has detected a higher than normal voltage signal coming from the transmission range switch, which is responsible for indicating the gear position of the transmission. The transmission range switch, also known as the neutral safety switch, plays a crucial role in ensuring that the vehicle starts only in Park or Neutral and shifts gears correctly. When the switch sends a high voltage signal, it can lead to incorrect gear selection, starting issues, and potentially unsafe driving conditions.

OBDII Code P0708 2015 GMC Sierra - Transmission Range Switch Circuit High Voltage
P0708 2015 GMC Sierra Code - Transmission Range Switch Circuit High Voltage

Common Causes of P0708 2015 GMC Sierra

  1. Faulty transmission range switch
  2. Wiring issues or short circuits in the transmission range switch circuit
  3. Corrosion or poor connections in the electrical system
  4. PCM software or hardware malfunction
  5. Fluid contamination affecting the transmission range switch

Symptoms of P0708 2015 GMC Sierra

  1. Difficulty starting the vehicle
  2. Inability to shift gears properly
  3. Harsh shifting or slipping gears
  4. Illumination of the Check Engine Light
  5. Loss of power or acceleration

How to Fix P0708 2015 GMC Sierra

  1. Begin by diagnosing the issue using a scan tool to confirm the P0708 code and checking the transmission range switch for proper operation.
  2. Inspect the wiring harness and connectors for any damage, corrosion, or loose connections. Repair or replace as necessary.
  3. Test the transmission range switch for proper voltage and resistance values. Replace the switch if it fails the test.
  4. Clear the code from the PCM memory and perform a test drive to ensure that the issue has been resolved.
  5. If the problem persists, further diagnostic procedures may be required to pinpoint the exact cause of the high voltage signal.

Cost to Fix P0708 2015 GMC Sierra

The typical repair costs for addressing a Transmission Range Switch Circuit High Voltage issue can range from $150 to $400, including parts and labor. However, it's essential to note that the actual cost can vary depending on the specific diagnosis time and labor rates at auto repair shops. Factors such as location, vehicle make and model, and engine type can also influence the final repair expenses. It's advisable to consult with local auto repair shops for a more accurate estimate tailored to your situation.

What does this mean?

Tech Notes for P0708 2015 GMC Sierra

The Internal Mode Switch (IMS) is mounted to the manual shift shaft detent lever as an assembly. The components of the detent lever/IMS assembly cannot be individually serviced. When the IMS needs replacing, the entire assembly must be replaced.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0708 2015 GMC Sierra Code

1. What does the P0708 code mean on a 2015 GMC Sierra?

The P0708 code indicates a high voltage issue in the transmission range switch circuit, which monitors the gear position.

2. What are the symptoms of a P0708 code on a GMC Sierra?

Common symptoms include difficulty shifting gears, the transmission staying in limp mode, the check engine light turning on, and inaccurate gear readings on the dashboard.

3. What causes the P0708 code to appear?

Possible causes include a faulty transmission range sensor, damaged wiring or connectors in the circuit, or issues with the vehicle's PCM (Powertrain Control Module).

4. Can driving with a P0708 code damage my GMC Sierra?

Driving with this code can cause further transmission damage if left unresolved, as it may lead to improper shifting or transmission overheating.

5. How do you diagnose a P0708 code?

Diagnosis involves checking the transmission range sensor, inspecting the wiring and connectors for damage, and testing the voltage and continuity in the circuit.

6. How do you fix the P0708 code on a 2015 GMC Sierra?

Possible repairs include replacing the transmission range sensor, repairing or replacing damaged wiring or connectors, and updating or reprogramming the PCM if necessary.

7. Is a P0708 code expensive to fix?

The cost depends on the exact repair needed. Replacing a transmission range sensor typically costs between $150 and $300, while extensive wiring repairs or PCM replacement can be more expensive.

8. Can a bad battery cause a P0708 code?

A weak or failing battery is unlikely to directly cause this code but could contribute to electrical issues that affect the transmission range sensor circuit.

9. Will clearing the P0708 code reset the problem?

Clearing the code may temporarily turn off the check engine light, but the underlying issue must be fixed to prevent the code from returning.

10. How does the transmission range sensor affect the vehicle's performance?

The transmission range sensor communicates the gear position to the PCM. If it malfunctions, it can lead to incorrect shifting, reduced performance, and safety concerns.

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