B1800 — 7 documented meanings by make

B1800 does not mean the same thing on every car — manufacturers reuse the number for different faults. 6 makes document it: Chrysler, Daihatsu, Ford, Mazda, Saab, Toyota. Find your make below.

B1800 on Chrysler

On Chrysler vehicles B1800 is documented as: Driver's door lock/unlock switch circuit/performance. B1800 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 Chrysler codes:

B1800 on Daihatsu

On Daihatsu vehicles B1800 is documented as: Driver's seat airbag squib, short circuit. B1800 points at airbag / restraint system. The standard definition names the system involved; which part inside it has actually failed is what the checks below establish, cheapest first.

Related Daihatsu codes:

B1800 on Ford, Mazda

On Ford, Mazda vehicles B1800 is documented as: Front turn signal light output, short circuit to positive. B1800 is stored when the ECU sees short to positive on the circuit named in the code (front). 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: Signal wire touching a permanently live wire in a damaged loom; Connector pins bridged by corrosion or a bent terminal; Internal fault in the component shorting the signal to supply; Incorrect wiring after an aftermarket accessory was fitted.

Check first, cheapest first:

1. Disconnect the component and check whether the signal line still reads battery voltage
2. Inspect the loom for melted or rubbed insulation, especially near heat sources
3. Check the connector for a pushed-back or bent terminal
4. Trace the signal wire back to the module, looking for a live wire running alongside
5. Repair the harness, or replace the component if it is shorting internally

Related Ford, Mazda codes:

B1800 on Saab

On Saab vehicles B1800 is documented as: Common output to all motors, open circuit; Common output to all motors, short circuit to ground; Common output to all motors, short circuit to positive. B1800 is stored when the ECU sees open circuit 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: Broken wire, most often at a flex point such as a door hinge or engine mount; Corroded or pushed-back terminal in the connector; Blown fuse on the supply side; Component failed with an internally open winding or element.

Check first, cheapest first:

1. Check the relevant fuse first — it is the cheapest thing that produces this code
2. Unplug and inspect both halves of the connector for corrosion and terminal fit
3. Continuity-test the wire end to end while flexing the loom by hand
4. Measure the component itself against its specification
5. Repair the break or replace the component, whichever the measurement points to

Related Saab codes:

B1800 on Toyota

On Toyota vehicles B1800 is documented as: Driver's side squib, short circuit. B1800 points at airbag / restraint system. The standard definition names the system involved; which part inside it has actually failed is what the checks below establish, cheapest first.

Related Toyota 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 B1800 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.