P06A7–P06A9 Sensor Reference Voltage B Circuit Range/Performance

Which code is which

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

The definition

P06A7: Sensor Reference Voltage B Circuit Range/Performance.

P06A7 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. 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.
2. Check the connector at the part for corrosion, and that it is fully seated.
3. Clear the code and see whether it returns, and under what conditions.

What actually causes this on a VAG

Your ECU generates its own small regulated supply - commonly around five volts - to feed sensors such as the accelerator pedal, boost or manifold pressure sensor, fuel rail pressure sensor and throttle position sensor. There is more than one of these supplies, and 'B' is the second. Range/performance means the voltage on that rail has drifted outside what the ECU expects, so every sensor sharing it starts reporting nonsense at the same moment. Expect reduced power and a long list of apparently unrelated sensor codes. Because the accelerator pedal sensor can sit on one of these supplies, the car can also cut to reduced power without warning, so don't put off looking at it.

Most likely causes, in order

1. One failed sensor dragging the rail down. Any single sensor on that circuit that shorts internally loads the supply for all the others, which is why so many faults appear together. The standard way to find it is methodical: with the fault present, unplug the sensors on that rail one at a time - when the rail recovers and the readings sober up, the last one you unplugged is the culprit. Do it somewhere safe rather than in traffic, because the engine may stumble or stall as sensors come off, and clear the extra codes the test itself stores.
2. Water or corrosion in a sensor connector. Sensors mounted low in the engine bay or out at the front where the charge air pipework runs take road spray, and damp bridging between pins pulls the reference voltage off. Unplug the likely candidates and look for green pins, moisture or crusty white residue in the connector body.
3. Chafed reference wiring. A reference wire that has rubbed through and is touching earth or a live feed does exactly the same thing as a shorted sensor. Follow the loom where it crosses brackets, the engine, or anything that vibrates against it, particularly if the fault started after recent work.
4. ECU internal regulator. The regulator inside the ECU that produces this supply can fail, but it is rare. Do not accept it as a diagnosis until every sensor on that rail has been disconnected in turn and the supply still misbehaves with nothing plugged into it.

Worth knowing: Several implausible sensors at once almost never means several failed sensors - it means one shared supply and one bad branch. Unplugging sensors one at a time until the rail recovers finds it in minutes and costs nothing, and it is what stops someone selling you a new ECU.

Common questions

What does P06A7 mean?

P06A7 means Sensor Reference Voltage B Circuit Range/Performance. The sensor still works, but its reading has drifted outside the window the ECU expects. That usually means a tired sensor or a problem with what it is measuring, not a broken wire.

Can I drive with P06A7?

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.

Related reading

• Battery Keeps Going Flat on a VW or Audi: Finding the Cause
• VW or Audi will not start: working out which problem you have
• Several warning lights on at once: usually one cause, not many
• Why the same fault code has completely different causes