OBD Code B1620: Wiper Rear Low Limit Input Circuit Open

Q: What does OBD code B1620 mean?

Wiper Rear Low Limit Input Circuit Open. The rear wiper motor circuit has an open connection, meaning the ECU can't detect the wiper's lowest position. Think of it like a light switch that's completely disconnected from the circuit—the system can't tell when the wipers are parked.

Q: What are the symptoms of fault code B1620?

Rear wiper won't operate or stops mid-sweep, Wiper control unresponsive or stuck in one position, Fault code displayed on dashboard

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What This Actually Means

In plain language — no jargon

The rear wiper motor circuit has an open connection, meaning the ECU can't detect the wiper's lowest position. Think of it like a light switch that's completely disconnected from the circuit—the system can't tell when the wipers are parked.

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Symptoms You May Notice

3 known symptoms for this code

Rear wiper won't operate or stops mid-sweep

Wiper control unresponsive or stuck in one position

Fault code displayed on dashboard

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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors a low-limit switch signal that activates when the rear wiper reaches its parked (lowest) position. This signal tells the motor when to stop, establishing a reference point. An open circuit prevents any voltage signal from reaching the ECU, breaking the feedback loop.

Voltage & Parameter Thresholds

Parameter	Normal Range	Fault Condition
Low Limit Switch Voltage	0.2–4.8V (switch closure detected)	5.0V+ (open circuit/no signal)
Circuit Resistance	Less than 10 ohms (closed)	Greater than 1 megohm (open)

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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

Wiring harness connector

Inspect and reseat the rear wiper motor connector at the liftgate; corrosion or loose pins often cause open circuits.

2

Wiring harness

Check the wiring between the liftgate and body for breaks, pinches, or damaged insulation; repair or replace as needed.

3

Rear wiper motor assembly

Replace the motor if internal low-limit switch contacts are faulty and wiring tests pass.

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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1620 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.

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How to Clear Code B1620

What happens after you fix the fault

Once the fault is repaired, B1620 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When

Fault has been diagnosed and repaired
You want to confirm the repair worked
Code appeared after a sensor was cleaned

⚠️ Do Not Clear When

Preparing for an emissions/PUC test
Root cause is still undiagnosed
Check engine light is flashing

Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.