P06A3: Sensor Reference Voltage D Circuit/Open
What to do
If the scan report lists several unrelated sensor faults, they are very probably all this one fault. Several sensors share a single power supply from the engine module, and when that supply fails they all stop reporting together.
Ask specifically whether the affected sensors share a reference supply before agreeing to replace any of them. This is the fault most likely to result in several parts being replaced unnecessarily.
Expect reduced power or limp mode, since the module is missing several inputs at once.
Mention any recent work in the engine bay or any accident repair, since a disturbed or pinched harness is a common cause.
What this code means
The fourth sensor reference voltage supply is open circuit.
Reference voltage codes are the ones to read first when a scan tool shows a page of unrelated sensor faults, and this corpus records that pattern repeatedly because it is the single most common way a diagnosis goes wrong.
Most sensors on an engine do not have their own power supply. The module provides a small number of regulated five-volt rails — labelled A, B, C, D and so on — and shares each one between several sensors. A pedal sensor, a pressure sensor and a position sensor may all sit on reference D.
So when this rail goes open, every sensor on it stops reporting at once. The scan tool then lists half a dozen faults that appear to have nothing in common, and each one individually looks like a failed sensor.
Chasing them one at a time is how a straightforward wiring repair becomes several unnecessary parts. Read the whole stored list, notice that the affected sensors share a supply, and fix the supply.
An open reference is usually a broken wire, a connector that has lost its terminal grip, or a module output stage that has failed — and the last of those is frequently the consequence of a short somewhere on the rail rather than an independent failure.
Which is why the rail should be checked for a short before a module is replaced. A new module fed into the same short fails the same way.
Likely causes
Start here
- Open circuit in sensor wiring · moderate
- Corroded or loose connector · easy
- Shorted sensor dragging the reference down · moderate
Less common
- Failed sensor reference voltage supply · specialist
- Damaged wiring harness · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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