B1621

Code

Other B — Body

Wiper Rear Low Limit Input Circuit Short To Battery

Brand: Other

Type: B — Body

Views: UK: 26 EN: 39 RU: 30

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Page language: EN

Causes

Wiring insulation damaged and contacting battery positive (B+)
Corroded or contaminated connector at the rear wiper motor or harness splice
Internal failure of the rear wiper motor park/low-limit switch (internal short to B+)
Aftermarket accessories or recent repairs that pinched or misrouted the harness
Water intrusion in the hatch/door area causing short to B+
Faulty BCM/wiper control module (less common)

Symptoms

MIL or body warning lamp may be illuminated
Rear wiper inoperative, stuck out of park, or does not park correctly
Erratic rear wiper behavior (runs continuously or will not park)
Stored trouble code B1621 in BCM or wiper control module
Possible fuse(s) related to wiper circuit may blow (if short is heavy)

What to check

Retrieve and record DTCs and freeze-frame data with a scan tool. Confirm B1621 is current or history.
Visually inspect rear wiper motor connector, harness, and grommet at the hatch hinge for damage, corrosion, or water intrusion.
With ignition ON, backprobe the low-limit input at the rear wiper connector and measure voltage. Compare to expected values below.
Disconnect the rear wiper motor connector and measure for continuity between the low-limit circuit and battery positive (B+)—with ignition OFF.
Inspect splices and inline connectors for signs of heat, corrosion, or repair wiring.
Wiggle the harness and operate the wiper while watching live data/voltage for intermittent changes.

Signal parameters

Normal (no short): low-limit input should be open/high-impedance or pulled to ground by the switch when in the low limit; measured voltage typically ~0 V (or near 0 V) when pulled low.
Fault condition (short to battery): low-limit input measures near battery voltage (~12 V) continuously when it should not.
When rear wiper motor is disconnected: continuity to B+ should be open/infinite for the low-limit circuit. Low resistance to B+ indicates a short.

Diagnostic algorithm

Verify and reproduce: Read/wipe the code with a scan tool and observe rear wiper behavior. Note whether the code is current or intermittent.
Visual inspection: Inspect harness routing, especially at the rear hatch hinge and grommet. Look for rubbed-through insulation, melted wire, or corrosion at connectors.
Backprobe voltage: With ignition ON (accessory or run as appropriate), backprobe the low-limit input at the rear wiper connector. If voltage is ~12 V when it should be low, a short to battery is present.
Isolate the motor: Turn ignition OFF and disconnect the rear wiper motor connector. Check for continuity between the low-limit circuit pin and battery positive. Continuity indicates wiring or internal motor short to B+.
Inspect/repair harness: If continuity to B+ is found with connector disconnected, trace the harness toward the body splice and BCM, repairing damaged insulation, connectors, or splices as needed.
Motor bench/test: If no short is found in the harness, suspect internal motor/switch. Replace or bench-test the rear wiper motor/park switch assembly and re-check for the short after replacement.
Re-check system: After repairs, clear codes, reconnect components, and exercise the rear wiper through several park cycles while monitoring for return of B1621.
Module check: If wiring and motor are verified good and the fault persists, consider BCM/wiper control module diagnosis per manufacturer procedures.

Likely causes

Chafed or pinched wiring at the rear hatch hinge or harness grommet
Corroded terminal or connector at the rear wiper motor/controller
Failed internal low-limit/park switch inside the rear wiper motor assembly
Short at a splice or connector where the circuit is tied to battery positive

Fault status

⚠️ Status

Stored when the rear wiper low-limit/park input circuit is detected at battery voltage (short to B+) when it should be open or pulled to ground, indicating a short to battery or internal motor switch failure.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours