OBD-II trouble code
P0708: Transmission Range Sensor "A" Circuit High
A range circuit stayed at reference voltage when the switch should have pulled it down. This is the mileage-driven failure in the family — contacts that have been wiped several hundred thousand times eventually stop making contact at all.
Quick facts
- System
- Powertrain
- Category
- Transmission / Shift Control
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $120 – $500
- DIY difficulty
- Intermediate DIY
What does P0708 mean?
The module holds each range circuit at a reference voltage through an internal pull-up resistor and waits for the switch to pull it to ground. P0708 is set when that never happens — the circuit sat at reference the whole time, in a range where the lookup table says it should have gone low. Electrically this is an open circuit, and every open circuit has the same three candidates: the wire, the ground, or the contact.
What gives this code its own character is which of those three usually wins. Unlike a grounded circuit, which tends to be caused by an external event — water, chafe, a pinched harness during a repair — an open range circuit is most often the result of ordinary wear inside the switch. A range sensor's contacts are wiped every single time the selector moves. A vehicle that has been shifted into and out of Park twenty times a day for fifteen years has cycled those contacts well over a hundred thousand times, and the plating on the wiper eventually wears through to base metal, oxidises, and stops conducting reliably. Nothing dramatic happened. The part simply reached the end of its service life.
That gives P0708 a distinct profile compared with its sibling codes. It is the quiet, gradual one. It usually appears on a high-mileage vehicle with no recent repair history and no weather correlation, often preceded by weeks of a gear indicator that flickered or dropped out briefly on one particular range before the code finally set. There is also a design distinction worth checking before you order anything: some manufacturers use a potentiometer-style range sensor rather than a multi-contact switch, and on those a high reading can equally mean the sensor's *ground* has opened rather than its signal. Testing the ground first on that style costs nothing and occasionally saves the whole repair.
Common causes
- Worn internal contacts in a high-mileage transmission range sensor — the most common cause by a wide margin
- Open or broken signal wire between the sensor and the module
- Open or high-resistance sensor ground circuit (especially on potentiometer-style sensors)
- Loose, backed-out or spread terminal in the sensor or module connector
- Connector not fully latched after a previous repair
- Sensor unplugged or left disconnected during other work
- Aftermarket sensor with contacts that do not close on the same sweep as the original
Symptoms
- Check engine light is on
- Gear indicator drops out or goes blank in one particular range
- Engine will not crank in the affected range but cranks in another
- Reverse lamps do not illuminate
- Transmission uses a fail-safe shift pattern or holds one gear
- Symptom built up gradually over weeks — a flickering indicator long before the code set
- No correlation with weather, washing or recent repair work
Diagnostic steps
- 1.Note the vehicle's mileage and history before testing. A high-mileage vehicle with no recent work and a symptom that crept in gradually is pointing at a worn switch, and the testing below is confirmation rather than exploration.
- 2.Watch the range PID through a full slow sweep of the selector and identify precisely which range fails to register. A single dead range is a worn contact; every range dead is power, ground or a connector.
- 3.Back-probe the affected signal circuit at the module connector and measure voltage while the selector is moved into that range. Reference voltage that never falls confirms the open.
- 4.With the sensor connected and the selector in the failing range, measure the voltage drop across the sensor ground. More than a few tenths of a volt means the ground is the fault, not the signal.
- 5.Wiggle-test the harness and both connectors while watching the PID. A reading that responds to gentle movement is a terminal problem and can be repaired without a new sensor.
- 6.Only after those three checks — signal, ground, connector — is the sensor itself confirmed. Replace and index it per the make's procedure, then verify all ranges register before returning the vehicle.
Repair cost
$120 – $500
Replacement is the usual outcome here rather than repair, because worn contacts cannot be restored. The sensor is $35 to $200 and fits in 30 to 60 minutes on external designs, putting the job at $150 to $350. Internal valve-body-mounted designs require dropping the pan and fluid and land nearer $400 to $500. A loose terminal or open wire repair, where that turns out to be the cause, is $100 to $200.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with transmission range sensor / neutral safety switch replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.