P0708 2018 GMC Sierra Code - Transmission Range Switch Circuit High Voltage
Quick Answer
The Transmission Internal Mode Switch (IMS) consists of 5 internal switches, A, B, C, P, and Neutral Start. Common causes include Faulty Transmission Internal Mode Switch (IMS), Transmission Internal Mode Switch harness is open or shorted, Transmission Internal Mode Switch circuit poor electrical connection. 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 2018 GMC Sierra indicates Transmission Range Switch Circuit High Voltage.
- Common causes
- Common causes include Faulty Transmission Internal Mode Switch (IMS), Transmission Internal Mode Switch harness is open or shorted, Transmission Internal Mode Switch circuit poor electrical connection.
- 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.
Code P0708 2018 GMC Sierra Description
The Engine Control Module (ECM) supplies a signal circuit to the neutral start switch. The ECM uses the state of the neutral start switch state as confirmation that the transmission is in neutral or park before the engine starter is engaged.
The Diagnostic Trouble Code (DTC) will be set when the TCM detects the internal mode switch is reporting an illegal range for greater than 1 s.
What are the Possible Causes of the DTC P0708 2018 GMC Sierra?
- Faulty Transmission Internal Mode Switch (IMS)
- Transmission Internal Mode Switch harness is open or shorted
- Transmission Internal Mode Switch circuit poor electrical connection
- Faulty Transmission Control Module (TCM)
How to Fix the DTC P0708 2018 GMC Sierra?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0708 2018 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Frequently Asked Questions about P0708 2018 GMC Sierra Code
1. What does the OBDII code P0708 mean on a 2018 GMC Sierra?
P0708 indicates a high voltage issue in the transmission range switch circuit, which monitors the gear selector position.
2. What are the common symptoms of the P0708 code on a 2018 GMC Sierra?
Symptoms may include the transmission being stuck in one gear, erratic shifting, a check engine light, or the vehicle entering limp mode.
3. What causes the P0708 code to appear on a 2018 GMC Sierra?
Common causes include a faulty transmission range sensor, damaged wiring or connectors, or issues with the powertrain control module (PCM).
4. Can I drive my 2018 GMC Sierra with the P0708 code?
It is not recommended to drive with this code as it may lead to further transmission damage or unsafe driving conditions.
5. How do I diagnose the P0708 code on a 2018 GMC Sierra?
Start by inspecting the transmission range sensor, checking for damaged or corroded wiring, and using a diagnostic scanner to monitor sensor voltage.
6. How do I fix the P0708 code on a 2018 GMC Sierra?
Repairs may involve replacing the transmission range sensor, repairing damaged wiring, cleaning connectors, or reprogramming the PCM if necessary.
7. How much does it cost to fix the P0708 code on a 2018 GMC Sierra?
The repair cost varies, but replacing the transmission range sensor typically costs $200–$400, including parts and labor.
8. Can a faulty battery cause the P0708 code on a 2018 GMC Sierra?
A weak or faulty battery can sometimes cause voltage-related issues, but it is less likely to directly trigger the P0708 code.
9. Does the P0708 code mean my transmission is failing on my 2018 GMC Sierra?
Not necessarily. The issue is often electrical, such as a faulty sensor or wiring, rather than a mechanical failure of the transmission.
10. Will clearing the P0708 code fix the problem on a 2018 GMC Sierra?
Clearing the code may temporarily turn off the check engine light, but the underlying issue must be resolved to prevent the code from returning.
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