B1622 Wiper Rear Low Limit Input Circuit Short To Ground

Introduction

The B1622 diagnostic trouble code (DTC) signals a fault within the rear wiper system of a vehicle, specifically indicating a short to ground in the low limit input circuit. This circuit is crucial for the proper functioning of the rear wiper, as it informs the body control module (BCM) or a similar control unit about the wiper's position. Addressing this issue promptly is vital to ensure the rear wiper operates correctly, maintaining visibility and safety.

Comprehensive Table: B1622 Wiper Rear Low Limit Input Circuit Short To Ground

Detailed Explanations

Definition: The B1622 DTC (Diagnostic Trouble Code) is a specific code generated by a vehicle's onboard diagnostic system. It pinpoints an electrical fault in the rear wiper system, specifically within the circuit responsible for the low limit input. This input is a signal the wiper motor sends to the vehicle's computer (usually the BCM - Body Control Module) to indicate that the wiper arm has reached its lowest point in its range of motion. A short to ground means that the wire carrying this signal is inadvertently making electrical contact with the vehicle's chassis or another grounded component, disrupting the normal electrical flow.

Symptoms: When the B1622 code is present, several symptoms can manifest, indicating a problem with the rear wiper system. The most obvious symptom is the rear wiper not functioning at all. Alternatively, the rear wiper might be stuck in a single position, unable to complete its sweep. Intermittent operation is also common, where the wiper works sporadically or unpredictably. In some cases, the wiper may operate continuously, even when switched off. In more severe situations, the short circuit can lead to a battery drain. Finally, the vehicle's computer may trigger a check engine light or other warning light to alert the driver of the issue.

Troubleshooting & Repair: Resolving a B1622 code requires a systematic approach to identify and rectify the underlying electrical fault. The first step is a visual inspection of the wiring and connectors associated with the rear wiper motor and switch. Look for any signs of damage, such as frayed wires, cracked insulation, or corroded terminals. Next, test the wiper motor and switch to ensure they are functioning correctly. This can be done using a multimeter to check for proper voltage and continuity. The core of the repair involves checking for shorts to ground with a multimeter. This is done by disconnecting the circuit and measuring the resistance between the wire in question and a known good ground point on the vehicle's chassis. A low resistance reading indicates a short. Inspect the BCM/Control Module for any signs of damage or corrosion, although this is less frequent. Depending on the findings, replace damaged wiring or components as needed. In some cases, particularly if the BCM/Control Module was involved, reprogramming the BCM/Control Module may be necessary after the physical repair.

Damaged wiring harness: The wiring harness that connects the rear wiper motor and switch to the BCM/control module is susceptible to damage from various sources. Vibration, heat, and exposure to the elements can cause the insulation to crack and wires to fray, leading to a short circuit. Rodents can also chew on the wires.

Faulty rear wiper motor/switch assembly: The wiper motor or the switch itself can develop internal faults that cause a short to ground. This can be due to wear and tear, corrosion, or physical damage.

Corroded connectors: Connectors are electrical connection points within the wiring harness. Over time, they can corrode due to exposure to moisture and road salt, leading to poor electrical contact and potential short circuits.

Defective BCM/Control Module: While less common, the BCM or other control module responsible for managing the rear wiper system can develop internal faults that trigger the B1622 code. This is usually a last resort diagnosis after all other possibilities have been exhausted.

Wiring harness rubbing against chassis: The wiring harness for the rear wiper is often routed through the vehicle's body. If the harness is not properly secured, it can rub against the chassis, eventually wearing through the insulation and causing a short to ground.

Incomplete or failed self-test: The vehicle's computer system performs periodic self-tests to check the functionality of various components. If the rear wiper circuit fails this self-test, it can trigger the B1622 code.

Wiper motor failure: A failing wiper motor can draw excessive current, potentially damaging the wiring and leading to a short circuit.

Short circuit in wiring: A direct short circuit in the wiring between the wiper motor, switch, and control module is the most common cause of the B1622 code.

BCM/Control Module malfunction: A malfunctioning BCM or control module can misinterpret signals from the wiper circuit or send incorrect commands, leading to the code.

Use a multimeter to check continuity and voltage: A multimeter is an essential tool for diagnosing electrical problems. It can be used to check for continuity (a complete circuit), voltage (electrical potential), and resistance (opposition to current flow).

Consult wiring diagrams for accurate testing: Wiring diagrams provide detailed information about the wiring circuits in the vehicle. Consulting these diagrams is crucial for accurate testing and troubleshooting.

Replace faulty components with OEM or equivalent parts: When replacing components, use OEM (Original Equipment Manufacturer) or equivalent parts to ensure proper fit and function.

Professional diagnostic tools may be required: Some diagnostic procedures, such as reprogramming the BCM/Control Module, may require specialized professional diagnostic tools.

Frequently Asked Questions

What does the B1622 code mean? The B1622 code indicates a short to ground in the rear wiper low limit input circuit, meaning the wire is making unintended electrical contact with the vehicle's chassis.

Can I fix the B1622 code myself? Depending on your mechanical and electrical skills, you might be able to fix it. Start with a visual inspection and basic multimeter tests. More complex repairs may require professional assistance.

What tools do I need to diagnose the B1622 code? You'll need a multimeter, wiring diagrams for your vehicle, and potentially a scan tool to read and clear the code.

How much will it cost to fix the B1622 code? The cost varies depending on the cause and the labor involved. A simple wiring repair might be inexpensive, while replacing the BCM/Control Module could be costly.

Is it safe to drive with the B1622 code? While generally safe, a malfunctioning rear wiper can impair visibility in inclement weather, potentially posing a safety risk. It's best to address the issue as soon as possible.

Conclusion

The B1622 DTC signals a problem with the rear wiper's low limit input circuit, most often a short to ground. A systematic approach to troubleshooting, including visual inspection, multimeter testing, and component replacement, is key to resolving the issue and restoring proper rear wiper function.