The P0708 code is a generic OBD-II diagnostic trouble code indicating “Transmission Range Sensor ‘A’ Circuit High.” It means the powertrain control module detected an abnormally high voltage in the transmission range sensor circuit.
This code does not automatically prove the sensor has failed. Diagnosis requires checking the sensor adjustment, inspecting the wiring for opens or shorts, and testing the circuit before replacing any components.
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Key Takeaways
- The P0708 code indicates the control module detected a high voltage condition or open circuit in the transmission range sensor signal circuit.
- Possible causes include a misadjusted sensor, damaged wiring, corroded connectors, or a failed transmission range sensor.
- Diagnosis involves verifying the gear selector alignment, inspecting the harness, and measuring the sensor’s signal voltage and resistance.
- Repairs may involve adjusting the sensor linkage, repairing wiring, or replacing the confirmed failed transmission range sensor.
P0708 Code Description and Implications
The P0708 code indicates that the powertrain or transmission control module detected a high voltage condition on the transmission range sensor circuit. This generic error code applies to vehicles equipped with automatic transmissions.
The transmission range sensor tells the control module which gear the driver has selected. The module uses this data to allow the engine to start in Park or Neutral and to control shift scheduling.
When the module detects that the signal voltage remains high when it should be pulled low, or detects an open circuit, it stores this code. This is an electrical fault that can prevent starting.
Common Causes of the P0708 Code
A misadjusted transmission range sensor or shift linkage is a primary cause. If the mechanical linkage does not perfectly align the sensor with the selected gear, the module may read an invalid voltage state.
Damaged wiring, chafed insulation, or corroded connectors in the harness between the control module and the sensor will interrupt the signal circuit or cause a short to voltage.
An internally failed transmission range sensor can create an open circuit condition, preventing the signal voltage from dropping and triggering the high input code.
Symptoms Associated With P0708
An illuminated Check Engine Light is expected once the monitor detects the circuit fault. MIL behavior varies by application, but the light commands when the electrical fault is verified.
You may experience a no-start condition. Because the module cannot verify the transmission is in Park or Neutral, the starter relay will not engage, preventing the engine from cranking.
In some applications, the transmission may enter a limp mode, the gear indicator on the dashboard may blank out, and shift quality may become harsh or erratic.
Diagnosing the P0708 Trouble Code
Diagnosis must begin by confirming the exact factory definition and checking for related transmission codes. Record freeze-frame data to see the conditions when the code set.
Verify the mechanical alignment of the shift linkage and the transmission range sensor. Ensure the gear selector physically matches the sensor position and the transmission manual valve.
Perform a thorough visual inspection of the wiring harness and connectors at the sensor and the control module. Look for chafed wires, broken insulation, corrosion, or loose pins.
Use a multimeter to test the signal circuit for continuity, shorts to voltage, and open circuits. Measure the sensor resistance and signal voltage across different gear positions.
Repairing the P0708 Issue
Repairs must follow confirmed diagnosis. If the shift linkage or sensor is misadjusted, realign the mechanical linkage and secure the sensor mounting bolts to the exact manufacturer specification.
If the wiring harness is found to be broken, shorted, or corroded, repair the circuit and secure the harness to prevent future damage from heat or moving components.
If electrical testing confirms the transmission range sensor is internally open or fails the manufacturer resistance test, replace the sensor using a component meeting the exact vehicle specification.
Cost Considerations for P0708 Repairs
Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.
Adjusting the shift linkage or repairing damaged external wiring involves minimal parts and moderate labor expenses.
If the transmission range sensor requires replacement, the cost of the component and the labor to access it will dictate the overall repair price.
Prevention Strategies for Future Occurrences
Inspecting exposed transmission wiring harnesses and connectors during routine under-vehicle service can help identify developing insulation damage or moisture intrusion before it causes an open circuit.
Keeping the shift linkage lubricated and ensuring the sensor seals are intact may reduce the risk of mechanical binding or moisture intrusion into the electrical connector.
Some electrical failures occur due to normal component aging and cannot be reliably prevented through standard maintenance.
Troubleshooting Tips and Best Practices
Do not attempt to fix a P0708 code by simply replacing the sensor without checking the mechanical linkage first. A bent shift cable is a frequent cause of this circuit code.
Always verify the reference voltage and ground circuits at the sensor connector before condemning the sensor itself. A missing ground will mimic an open circuit or high voltage condition.
Check for technical service bulletins for your exact vehicle application, as some manufacturers release updated shift linkage components or revised sensor designs to address chronic alignment issues.
More OBD-II Codes
| P0707 | P0706 | P0705 | P0704 |
| P0703 | P0700 | P0711 | P0713 |
| P0714 | P0715 | P0716 | P0717 |
| P0730 | P0740 | P0750 | P0760 |
| P0770 | P0780 | P0850 | P1700 |
| P1705 | P1715 | P1720 | P1738 |
Frequently Asked Questions
Is the P0708 code generic or manufacturer-specific?
Yes, P0708 is a generic SAE OBD-II diagnostic trouble code. However, the exact transmission range sensor design and testing procedures vary by manufacturer and vehicle application.
Will a P0708 code prevent my car from starting?
Yes. The control module uses this sensor to verify the transmission is in Park or Neutral before engaging the starter. A circuit fault can prevent the engine from cranking.
Does a P0708 code mean my transmission is broken?
Not necessarily. This code indicates an electrical circuit fault or mechanical misalignment in the range sensor. It does not automatically prove internal transmission gears or clutches have failed.
Can a bad shift cable cause a P0708 code?
Yes. A stretched, bent, or misadjusted shift cable can prevent the transmission range sensor from aligning correctly with the selected gear, triggering the high circuit code.
Can I clear the P0708 code without fixing the problem?
Clearing the code only resets the warning light. If the underlying wiring fault, misadjustment, or failed sensor remains, the monitor will detect the condition immediately and turn the light back on.
What Should You Do About the P0708 Code?
Confirm the exact factory definition and check for related transmission codes for your specific vehicle application. Follow the applicable manufacturer diagnostic procedure to verify whether the fault lies in the linkage, wiring, or sensor.
Once testing confirms the root cause, repair or replace the confirmed failed component in the relevant system, then retest the gear position signals to ensure the control module reads the correct transmission state.
