B1620 — Wiper Rear Low Limit Input Circuit Open

OBD2 code B1620 flags a problem with the body electrical system (wiper rear low limit input circuit open). The car is usually drivable while you plan the repair. Common culprits: corroded or loose connectors, body control module (BCM) fault, blown fuse or failed relay.

body electrical

Is it safe to drive?

Short-term driving is OK Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm B1620 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many B0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the body electrical system for damage, corrosion, chafing or poor contact.
Subsystem check Do a continuity test end-to-end on the wiper rear low limit input circuit and wiggle the harness while measuring — intermittent opens show up as fluctuating readings.
Subsystem check Operate the affected function while watching its switch and motor PIDs in live data.
Subsystem check Inspect connectors and wiring at flex points (door jambs, tailgate hinges) — wires break there first.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm B1620 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1620 (parts and labor, USD, independent shop rates): BCM repair or replacement: $300–$900; Replace the switch or actuator: $120–$450; Repair wiring or connectors: $80–$250. Overall, fixing B1620 usually costs between $80 and $900. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

Is it safe to drive with B1620?

Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

How do I diagnose B1620 myself?

Start with a scan: confirm B1620, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the wiper rear low limit input, and verify the suspect component against live data before buying parts.

Will B1620 clear itself?

Sometimes B1620 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

How much does it cost to fix B1620?

BCM repair or replacement — $300–$900; Replace the switch or actuator — $120–$450; Repair wiring or connectors — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What is the most common cause of B1620?

The most common causes are: corroded or loose connectors, body control module (BCM) fault, blown fuse or failed relay.

The rear wiper system on modern vehicles relies on a small but important feedback signal: the low-limit input. This signal tells your body's control module when the wiper blade has reached its lowest resting position. When the circuit responsible for carrying that signal develops a break, the module logs code B1620. The computer doesn't set this code after a single failed reading—it confirms the problem across multiple ignition cycles before triggering the warning light. Think of it as the system double-checking itself to avoid false alarms.

When technicians describe a "circuit open," they're referring to an interrupted electrical path. Current cannot flow through the broken section, leaving the module in the dark about the wiper's actual position. This isn't a case of low voltage or a weak ground—it's a complete break somewhere in the loop. Common culprits include a cut wire, a connector that has worked loose, corrosion eating through terminals, a blown fuse, or even an internal failure inside the wiper motor assembly itself. The freeze frame data stored alongside B1620 captures engine load, RPM, coolant temperature, and vehicle speed at the exact moment the fault occurred—valuable information for recreating the failure during diagnosis.

The good news is that B1620 lives in the body electrical group, not the engine management system. Most drivers will notice no change in how the car drives, steers, or stops. The impact is limited to the rear wiper function and whatever other features share that circuit. You may lose the rear wiper entirely, see it operate erratically, or notice the dashboard warning light illuminate without any other obvious effect.

Common Symptoms of B1620

Rear wiper fails to operate or moves only partially before stopping
Intermittent operation of the rear wiper with no predictable pattern
Dashboard warning light stays illuminated after the fault is detected
Other body functions on the same circuit (if applicable) operate unpredictably
No effect on engine performance, transmission operation, or braking systems
The rear wiper may make a clicking sound without actually moving

What Causes B1620?

The most frequent cause is a blown fuse protecting the rear wiper circuit. Modules rarely fail before simpler explanations are ruled out.

Blown fuse in the rear wiper feed circuit
Connector at the rear wiper motor or limit switch is unplugged or has a backed-out pin
Heavy corrosion on connectors caused by water intrusion or road salt
Broken wire in the harness near the tailgate or rear hatch—these areas flex constantly
Body control module (BCM) internal failure
Internally open wiper motor or limit switch
Poor ground connection at the wiper motor assembly
Wiring damaged by chafing against body panels or trim

How to Diagnose B1620

Start with a scan tool to confirm the code and understand what the vehicle was doing when the fault triggered.

Connect an OBD2 scanner and verify B1620 is stored in the body control module. Record the freeze frame data showing engine conditions at the time of failure—this tells you whether the fault appears during cold starts, high speeds, or specific weather conditions.
Check for related body codes. A cluster of B0xxx codes often points to a shared power supply or ground problem rather than individual component failures. Search for any TSBs (Technical Service Bulletins) for your specific make and model year that address wiper circuit issues.
Visually inspect the rear wiper harness where it bends at the tailgate hinge. This flex point fatigues wires over time. Pull back any weatherstripping and look for broken strands or rubbed-through insulation.
Test continuity on the low-limit input circuit from the BCM to the motor assembly. An open reading confirms the break. Gently wiggle the harness during testing—intermittent opens will show as fluctuating resistance.
Verify battery voltage reaches the motor connector when the wiper is commanded on. No voltage indicates an upstream problem. Check the ground path separately with a resistance test.
Inspect and clean the motor connector if corrosion is present. Apply dielectric grease after reassembly to prevent future moisture damage.
Clear the code, perform a complete drive cycle including the conditions from the freeze frame, and verify B1620 does not return.

Repair Options and Costs

Prices below reflect typical U.S. independent shop rates for parts and labor.

BCM repair or replacement: $300–$900
Wiper motor or switch replacement: $120–$450
Wiring harness repair or connector replacement: $80–$250

Total Repair Cost for B1620

The final bill depends entirely on what caused the circuit to open. In most cases, the problem is a blown fuse or a loose connector—repairs in the $80–$150 range. Wiring damage inside the tailgate harness pushes costs toward $200–$250 if you find an experienced technician who can splice without replacing the entire harness. BCM replacement is the most expensive scenario at $300–$900 and should only be considered after the harness and connections are thoroughly verified. Budget $80–$900 total, with the average repair falling somewhere in the middle depending on your vehicle's complexity.

Can You Drive with B1620?

Generally yes. Body control codes rarely compromise engine operation or safety-critical systems. However, losing the rear wiper in heavy rain or snow is a legitimate safety concern if visibility suffers. Central locking faults stored alongside B1620 could theoretically leave your vehicle unsecured. Use your judgment—if the rear wiper is your only rear visibility aid in wet conditions, address this code sooner rather than later.