OBD2 code P0708 is defined as “Transmission Range Sensor Circuit High Input,” indicating that the sensor responsible for determining the transmission’s position (such as Park, Reverse, Neutral, Drive) is sending a signal outside of the expected range to the vehicle’s control module.
This can lead to a variety of transmission issues, including erratic shifting, the inability to start in certain gears, and even the activation of the check engine light. The code points to a problem in the transmission range sensor or its circuit, impacting the overall performance and safety of the vehicle.
P0708 quick overview
| Meaning | P0708: Transmission Range Sensor Circuit High Input |
| Is it serious? | Yes, this code can lead to transmission operational issues, potentially affecting vehicle safety and drivability. |
| Possible causes | – Faulty or misadjusted transmission range sensor – Wiring issues (open, short to power) – Corrosion or poor connections in the sensor’s connector – Faulty Transmission Control Module (TCM) |
| How to diagnose? | Inspect the transmission range sensor: Check for proper adjustment and physical condition. Check wiring and connectors: Look for damage, corrosion, or shorts. Measure voltage and resistance: Verify the sensor’s output is within specifications. Swap components if possible: Use parts from a known good vehicle to test. Refer to technical service bulletins (TSBs): Check for known issues and solutions. Examine the TCM: Consider its condition, especially under varying temperatures. |
P0708 Meaning
Imagine the transmission range sensor as a translator that communicates your gear selection to the car’s computer. If this translator starts speaking in a language the computer can’t understand (sending a signal too high), the computer gets confused.
This confusion can manifest as problems with shifting gears, showing the wrong gear on the dashboard, or even preventing the car from starting properly. The issue might stem from the sensor itself, the wires connecting it to the computer, or even the computer’s ability to understand the signals, all of which are crucial for a smooth driving experience.
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How to fix P0708 – learn from mechanics
I looked into P0708 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Chevrolet
Vehicle information 2010 Chevrolet Silverado 3500 HD LT 6.6L
Issue + repair history
- Intermittent problem with 1-2 shift
- MIL Lamp on
- Codes: P0708 (Internal Mode Switch), P0762 (Shift valve jammed)
- Symptoms:
- Good upshifts and downshifts when codes are cleared
- Check engine light illuminated intermittently
- Cruise control disengages
- PRNDL indicator fails to show shifter position
- Slippage when stopping and taking off
- Clunking during shifting when codes are present
- Previous repairs:
- Installed internal wiring harness due to leakage into external connector
- Changed filters and fluid
Other OBD2 Codes + Test Results
- OBD2 Codes:
- P0708 – Internal Mode Switch
- P0762 – Shift valve jammed
Mechanic suggestions
- Locate and inspect the Internal Mode Switch (IMS) inside the valve body attached to the manual shift lever shaft
- Investigate the Transmission Control Module (TCM) for potential failure, especially if it works when cold but fails when hot
- Consider swapping modules from a donor vehicle to test functionality
- Use diagnostic tree tests to identify specific parameters related to the codes
Final fix Discovered the issue with the Internal Mode Switch located inside the valve body. Confirmed by checking resistance on the mode switch wires from the transmission.
Case #2: Hyundai
Vehicle information 2006 Hyundai Elantra GLS 2.0L
Issue + repair history
- MIL Lamp on
- Code: P0708 (Transmission position range switch high)
- Symptoms:
- Code returned after switching sensor for a known good part and test driving
- Pinpoint test did not reveal any faults
- Previous repairs:
- Installed another switch and carefully checked harness connections
Other OBD2 Codes + Test Results
- OBD2 Codes:
- P0708 – Transmission position range switch high
Mechanic suggestions
- Check for any Technical Service Bulletins (TSBs) related to the issue (e.g., TSB 09-AT-013)
- Investigate possible causes such as an open or short in the transaxle range switch, faulty transaxle range switch, or faulty PCM
- Measure voltage at all pins in the connector, ensuring 0V at all terminals except pin 8 which should be B+
- Inspect connections closely for pushed out pins and harness for rubbed-through wiring
- Utilize resources like www.hmaservice.com for factory manuals and TSB information
- Check for proper adjustment of the range switch, ensuring alignment in the N position
Final fix Successfully installed another switch and carefully checked harness connections, following new instructions. Issue resolved.
Case #3: Mazda
Vehicle information 1996 Mazda B4000 LE 4.0L
Issue + repair history
- MIL Lamp on
- Codes: P0713 (Transmission range sensor), P0708 (Transmission fluid temperature)
- Symptoms:
- Truck starts up but won’t start in gear, indicates it’s in drive all the time
- Voltage reading at the computer for transmission range sensor is consistently 5 volts in all gears
- Attempted repair:
- Replaced transmission range sensor but problem persisted
- Found ground wire from battery to frame was repaired, resolving the issue
Other OBD2 Codes + Test Results
- OBD2 Codes:
- P0713 – Transmission range sensor
- P0708 – Transmission fluid temperature
Mechanic suggestions
- Confirm the condition of the ground circuit, as both sensors share a ground circuit and an open circuit is likely
- Obtain the wiring diagram to locate and inspect the common ground for the sensors
- Consider adding a ground strap from the frame to the engine to ensure adequate grounding
- Check all ground connections thoroughly
Final fix Repaired the ground wire from the battery to the frame, resolving the issue with both P0713 and P0708 codes.
How to diagnose P0708
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Brief Explanation |
|---|---|
| Inspect the transmission range sensor | Check for proper adjustment, damage, or wear. |
| Check wiring and connectors | Look for damage, corrosion, or poor connections affecting the signal. |
| Measure voltage and resistance at the sensor | Ensure the sensor’s output matches the manufacturer’s specifications. |
| Swap components with a known good vehicle | Test functionality with parts from another vehicle to pinpoint issues. |
| Refer to technical service bulletins (TSBs) | Check for any manufacturer-advised issues and fixes related to P0708. |
| Examine the Transmission Control Module (TCM) | Assess for faults that might arise under different temperature conditions. |
Leveraging real service cases offers a practical approach to diagnosing and fixing the issues associated with P0708. Addressing the root causes, such as sensor maladjustment, wiring problems, or TCM issues, is key to resolving this code and restoring normal transmission function.
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko