B1245

Wiper Rear Motor Run Relay Circuit Short to Battery

Body Chassis/Safety Wiper System 🟢 Low — Fix at next service ✅ Safe to Drive
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What This Actually Means

In plain language — no jargon

The rear wiper motor relay circuit is shorted directly to battery power, meaning electricity is flowing where it shouldn't. It's like a wire touching the positive terminal of a battery when it shouldn't be connected there at all.

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Symptoms You May Notice

3 known symptoms for this code
Rear wiper motor runs continuously or won't turn off
Rear wiper inoperative despite control switch operation
Burning smell or visible damage near rear wiper motor relay
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors the voltage at the rear wiper motor relay control circuit. It detects when voltage remains at battery level (12-14V) during normal operation when it should be ground-switched or pulse-modulated. The fault triggers when sustained high voltage is detected instead of controlled relay switching patterns.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Relay Control Voltage 0V to 5V (ground-switched signal) Sustained 12-14V (battery short)
Circuit Resistance High impedance when inactive Low/zero resistance indicating short path to battery
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Rear wiper motor relay
Locate relay in underhood fuse box, remove and inspect for corrosion or internal short, then replace with OEM relay.
2
Wiring harness connector
Disconnect rear wiper motor connector and inspect for corroded pins, water damage, or exposed conductors causing short to battery.
3
Rear wiper motor assembly
If relay and wiring are good, replace the motor unit as internal short may be present in motor windings or switch.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1245 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 B1245

What happens after you fix the fault

Once the fault is repaired, B1245 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.