P0788–P078D Shift Timing Solenoid A High
The ECU has logged a fault on P0788. The definition below is the exact wording the standard uses for this code.
Can you drive it? 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.
Which code is which
Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.
| Code | Definition | Severity |
|---|---|---|
P0788 | Shift Timing Solenoid A High | Investigate soon |
P078D | Shift Timing Solenoid B High | Investigate soon |
The definition
P0788: Shift Timing Solenoid A High.
P0788 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:
- Read the freeze-frame data stored with the fault - engine speed, load and temperature at the moment it logged tell you whether this happens cold, hot or under load.
- Check the connector at the part for corrosion, and that it is fully seated.
- Clear the code and see whether it returns, and under what conditions.
What actually causes this on a VAG
The mirror image of the 'low' code: the transmission control unit is seeing a higher voltage than expected on that shift timing solenoid's control circuit. In real terms 'high' most often means the circuit is broken - an open wire or a disconnected plug - or that it has touched a positive feed, so the valve cannot be driven at all. Expect limp home, a fixed gear and a warning light. As with the rest of this family, the letter 'A' and the phrase 'shift timing solenoid' are generic wording; a VAG-capable tool will identify the actual valve.
Most likely causes, in order
- Open circuit or a plug that is not fully latched. Check the gearbox connector is properly clipped home. This is especially likely if the car has recently had work near the gearbox - clutch, starter, engine mount, subframe or sump - where the plug is easy to disturb or leave half seated.
- Broken or chafed wire in the gearbox loom. Look where the harness runs over the bellhousing or crosses metalwork, and for shiny or rubbed insulation. A break can hide inside the outer sleeving, so flex the loom while the fault data is being watched.
- Open winding inside the solenoid. The coil has gone open circuit and simply cannot draw current. A workshop can compare it with the other solenoids in the same unit before committing to valve body work.
- Control unit output stage. Genuine but uncommon, and only a fair conclusion once the wiring, the connector and the solenoid itself have been checked.
Worth knowing: Because 'circuit high' usually just means the circuit is open, a disturbed connector or a single broken wire is far more likely than a dead gearbox. If this appeared immediately after garage work or a battery disconnection, start with what was touched rather than pricing up a mechatronic. Do not treat limp home as something to live with in the meantime - a box locked in one gear leaves you without the acceleration you expect for joining a motorway or overtaking.
Reading the code is the easy part
A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.
VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.
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Common questions
What does P0788 mean?
P0788 means Shift Timing Solenoid A High. It is logged when the ECU sees this circuit outside its expected operating window.
Can I drive with P0788?
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.