B1873 — Turn Signal / Hazard Power Feed Circuit Short To Ground

The diagnostic trouble code B1873 indicates a short circuit in the power feed circuit related to turn signals or hazard lights. This code points to an electrical fault that affects the vehicle’s signaling system, specifically a possible short to ground in the power supply wiring. It’s important to note that labels for this code may vary between different vehicle manufacturers, which can influence how the fault is identified or reported in diagnostic tools.

Manufacturer variations for trouble code B1873

Because different vehicle manufacturers may use various coding labels and descriptions for similar issues, the label related to the B1873 code can differ. It is essential to cross-reference the specific vehicle’s repair manual or diagnostic scanner to ensure accurate diagnosis. Here are some known variations:

• BMW: 613E — Short to ground, turn signal / hazard circuit
• Volkswagen / Audi: 00563 — Turn signal/hazard circuit shorted to ground
• Ford: U1356 — Power feed circuit to turn signals or hazard lights shorted
• Mercedes-Benz: 204A — Fault in power supply for signaling system
• Peugeot / Citroën: EC68 — Short circuit in turn signal/hazard wiring

What does trouble code B1873 mean?

Behind the B1873 code lies an electrical issue detected in the vehicle’s turn signal or hazard lighting circuit. The ECU (Engine Control Unit), which is the vehicle’s central computer, continuously monitors these circuits for faults. When it detects a short to ground—meaning a direct connection between the circuit’s power feed and ground—a predefined fault is stored, and the warning light or message may be triggered.

This code typically appears when there’s an unintended electrical connection causing excess current to flow through the circuit, risking damage to the switch, wiring, or peripheral components. It might occur after work has been done on the vehicle’s lighting system, or it can happen randomly due to wiring deterioration.

Severity and risks of trouble code B1873

The B1873 code is classified as a moderate severity issue. If left unresolved, it can lead to multiple electrical problems, including blown fuses, damaged switches, or wiring degradation. The hazard is that a short circuit can potentially cause wiring fires in extreme cases, although this is less common.

In terms of drivability, this trouble code generally results in malfunctioning lighting components—such as turn signals or hazard warnings—without directly affecting vehicle operation. However, because signaling is a critical safety feature, addressing the issue promptly is advisable. Can the vehicle be driven with this code? Yes, but only with caution and understanding that lighting signals may not function properly.

Symptoms of trouble code B1873

Drivers or technicians might notice various issues when this code is active. Common symptoms include:

• Failing turn signals or hazard lights that do not activate or blink irregularly.
• Warning lights or messages on dashboard related to signaling or electrical faults.
• Intermittent lighting issues, where signals work sometimes but not consistently.
• FUSE blowouts related to the lighting circuit.
• Unusual electrical behaviour in the switch or wiring harnesses associated with signaling.

Most likely causes of trouble code B1873

The causes of this fault are typically linked to electrical issues within the signaling circuit. While specific causes can vary depending on vehicle make and model, common underlying problems include:

1. Short circuit in the wiring harness: Damage or wear causing the power feed to connect directly to ground.
2. Faulty turn signal or hazard switch: A defective switch may create an internal short or cause electrical failures.
3. Corroded or damaged connectors: Corrosion, dirt, or loose connections can lead to unintended grounding.
4. Damaged lighting components: Faulty bulbs or assemblies with internal wiring issues can induce a short.
5. Aftermarket modifications or repairs: Incorrect wiring during aftermarket installation may lead to shorts.

How to diagnose trouble code B1873

Diagnosing this issue involves a combination of visual inspection and electrical testing. Here are the recommended generic steps:

1. Visual inspection: Check wiring and connectors associated with the turn signals and hazard lights for obvious damage, corrosion, or loose connections.
2. Check fuses: Inspect relevant fuses for blowout, indicating a possible circuit short.
3. Test switches and relays: Verify that the turn signal and hazard switches are functioning properly and not internally shorted.
4. Live data monitoring: Use a diagnostic scanner to monitor the circuit’s voltage during operation, observing for abnormal voltage drops or grounding indications.
5. Continuity and resistance tests: Perform electrical tests on wiring and components to identify any shorts to ground.

Possible repairs for trouble code B1873

Repair strategies primarily depend on identifying the root cause found during diagnosis. Common repairs include:

• Repair or replace damaged wiring harnesses: A professional job, especially if wiring is frayed, corroded, or melted.
• Replace faulty switches or relays: Basic repair that addresses internal electrical faults in control components.
• Reconnect or replace damaged connectors: Ensures proper electrical contact and prevents shorts.
• Correct aftermarket wiring issues: Rewire or remove incorrect wiring modifications.
• Replace faulty bulbs or lighting assemblies: If an internal short in a light component is identified.

Vehicles commonly associated with trouble code B1873 in Europe

This code is generally related to a broad range of European vehicles, especially those with complex electrical systems. Vehicles from well-known brands such as Volkswagen, Audi, BMW, Mercedes-Benz, Peugeot, and Citroën frequently encounter issues affecting turn signal and hazard lighting circuits.

Frequent mistakes with trouble code B1873

During diagnosis and repairs, certain mistakes are common that may prolong the resolution or cause further issues. Some include:

• Assuming the fault is solely in the switch: Without inspecting wiring or connectors.
• Ignoring visual damage: Overlooking obvious wiring deterioration or corrosion.
• Using incorrect testing procedures: Applying inappropriate electrical tests that do not reflect real-world conditions.
• Replacing parts without proper diagnosis: Such as swapping switches or relays prematurely.
• Neglecting vehicle-specific wiring diagrams: Which are critical for accurate diagnosis.

FAQ — trouble code B1873

Can this code disappear on its own? No. This fault indicates a physical electrical issue that requires repair. Clearing the code may temporarily turn off the warning, but if the underlying issue remains, the code will return.

Can I keep driving? Yes, but with caution. The vehicle may have functioning turn signals and hazard lights, but electrical faults can worsen, risking further damage. If signals are essential for your safety or if the warning persists, it’s best to have the vehicle inspected promptly.

Why does the code return after clearing? This happens when the underlying issue—such as damaged wiring, a faulty switch, or a short circuit—has not been repaired. The ECU re-detects the fault during system checks once the code is cleared.