B1559 — 3 documented meanings by make

B1559 does not mean the same thing on every car — manufacturers reuse the number for different faults. 4 makes document it: Ford, Jaguar, Mazda, Suzuki. Find your make below.

B1559 on Ford, Mazda

On Ford, Mazda vehicles B1559 is documented as: Door lock cylinder circuit. B1559 points at door / window / lock. The standard definition names the system involved; which part inside it has actually failed is what the checks below establish, cheapest first.

Related Ford, Mazda codes:

B1559 on Jaguar

On Jaguar vehicles B1559 is documented as: Door key barrel circuit. B1559 points at immobiliser / key. The standard definition names the system involved; which part inside it has actually failed is what the checks below establish, cheapest first.

Related Jaguar codes:

B1559 on Suzuki

On Suzuki vehicles B1559 is documented as: Ignition power supply voltage data malfunction. B1559 is stored when the ECU sees malfunction on the circuit named in the code. That describes how the circuit is behaving, not which part has failed — the wiring, the connector and the component itself can all produce it, which is why the checks below start with the cheapest.

Usually one of: Wiring or connector fault in the circuit; Component failed electrically; Supply or ground problem feeding the circuit; Controlling module fault, though this is the least common of the four.

Check first, cheapest first:

1. Read all stored codes — a general fault code is often the symptom of a more specific one
2. Inspect the connector and wiring for the named component
3. Check supply and ground at the component
4. Measure the component against specification
5. Replace the component once wiring and supply are ruled out

Related Suzuki codes:

Which one is yours

A generic OBD reader gives you the number, not which of these meanings your manufacturer assigned to it. To get to the specific one:

1. Use a brand-specific scanner — VCDS for VAG, INPA or ISTA for BMW, XENTRY for Mercedes, Forscan for Ford. It shows the manufacturer's own text rather than the generic one.
2. Read all stored codes together — the neighbouring ones usually point at which system is involved and narrow the list.
3. Check freeze-frame data: the RPM, temperature and load at the moment it triggered indicate which system was active.
4. If you have no brand scanner, tell me the make and model below and I will tell you which of these applies to your car.

Code family

B1xxx is body systems, manufacturer-specific.

Severity

Manufacturer-specific body system — needs a brand scanner to read the actual cause.

That is what holds for B1559 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.