P0708–P2803 Transmission Range Sensor A Circuit High

Which code is which

Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.

The definition

P0708: Transmission Range Sensor A Circuit High.

P0708 is a powertrain code (the engine or gearbox), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.

What to check first

Cheapest and fastest checks first:

1. Unplug the sensor and check whether the signal falls. If it stays high, suspect the wiring rather than the sensor.
2. Check the earth path - a missing earth makes a sensor read high.

What actually causes this on a VAG

Here the selector position signal is sitting high, at or near battery voltage, when it should not be. On these gearboxes that usually means the circuit is broken somewhere so nothing is pulling the wire down, though a wire rubbed through onto a permanent live does the same thing. As with the other range codes, the visible symptoms are a car that will only start in one selector position or not at all, reverse lights that do not work, or a gearbox that stays in a safe gear. An open circuit here normally fails in the cautious direction - the car will not crank rather than cranking when it should not - but it will still leave you stranded. Again, this describes the wiring and the sensor, not the gears.

Most likely causes, in order

1. Connector at the gearbox open, corroded or oily. A plug left unlatched after a service, a broken locking clip, a pin pushed back out of the housing, corroded contacts, or gearbox oil that has crept along the inside of the wires and coated the pins - any of these gives an open circuit. Check this first on any car that has recently had gearbox, starter, subframe or exhaust work. Unplug it fully, inspect the pins for corrosion and for one sitting deeper than the others, and refit until it clicks. If you find an oily film inside the connector body, the affected loom section usually needs replacing rather than cleaning, because the oil will keep wicking through.
2. Broken wire in the loom. Wires break where they flex, typically just behind the connector or where the loom crosses from the body to the gearbox and moves with the engine. The insulation often looks untouched while the copper inside has parted. Gently flex the loom in sections with the ignition on and watch for the live position value to jump.
3. Failed multifunction switch or position sensor. An internally open contact in the switch produces the same picture as a broken wire. Confirm by measuring at the gearbox connector rather than by substitution, since these parts are not cheap and the loom is by far the more common culprit. Splitting the circuit at that plug tells you immediately which side of it the open is on.

Worth knowing: A high or open circuit is the one fault in this family where a careful look at the connector really can solve it for nothing, so make that the first job of the day. Resist any suggestion of a mechatronic unit or a gearbox overhaul off the back of this code: it is describing a wire that is not connected to anything. And as with the other range codes, reverse lights that have stopped working are a roadworthiness failure in their own right.

Common questions

What does P0708 mean?

P0708 means Transmission Range Sensor A Circuit High. The voltage on this circuit is sitting near battery voltage. Typically a short to a positive feed, or a disconnected sensor floating high.

Can I drive with P0708?

The engine light will stay on and the car may run in a reduced-power mode. Read the freeze-frame data to see the conditions the fault was logged under.

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