B1245

What Does Code B1245 Mean?

DTC B1245 signifies a fault within the rear wiper motor run relay circuit, specifically indicating a short to battery voltage. This code is typically set by the Body Control Module (BCM) or General Electronic Module (GEM), which is responsible for monitoring and controlling various body electrical functions, including the rear wiper system. The BCM/GEM continuously monitors the voltage on the output side of the rear wiper motor run relay, or potentially the relay’s control circuit. When the rear wiper system is commanded off, or the relay is de-energized, the BCM expects to see a low voltage state (near 0V or ground) on the circuit supplying power to the rear wiper motor. If, however, the BCM detects a constant or unexpectedly high voltage, typically approaching battery voltage (around 12V), on this circuit when it should not be present, it interprets this as an unintended short to battery voltage. This abnormal voltage signal indicates that current is flowing or is present on the circuit independent of the BCM’s command, often leading to unintended operation or preventing proper control of the rear wiper motor.

Common Symptoms

• Rear wiper operates continuously, even when the wiper switch is in the “off” position.
• Rear wiper motor does not operate at all, possibly due to a blown fuse caused by the short, or the BCM disabling the circuit.
• Rear wiper is stuck in a specific position on the window.
• Battery drain over time if the short is constant and continuously energizes a component.
• A fuse for the rear wiper circuit may be repeatedly blowing.

What Causes the Code B1245?

• Faulty Rear Wiper Motor Run Relay: An internal malfunction within the relay, causing its contacts to stick in the closed position or an internal short that routes constant battery voltage to the output terminal.
• Damaged Wiring Harness: A specific wire within the rear wiper motor run relay circuit has chafed or otherwise sustained damage, causing it to come into direct contact with another wire carrying constant battery positive voltage. This is particularly common in areas subject to movement, such as the tailgate hinge or wiring pass-throughs.
• Corroded or Damaged Connectors: Corrosion bridging terminals within the rear wiper motor relay socket or at the rear wiper motor connector itself, inadvertently creating a pathway for battery voltage.
• Internal Fault in the Rear Wiper Motor: Although less common for a “short to battery on the relay circuit” code, a severe internal short within the wiper motor itself could, in rare instances, backfeed voltage or draw excessive current, causing related circuit anomalies.
• Faulty Body Control Module (BCM) / General Electronic Module (GEM): A rare internal defect within the BCM/GEM, where the module’s internal monitoring circuit or a driver transistor is shorted to voltage, falsely registering or causing the condition.

How to Diagnose and Troubleshoot

Diagnosing B1245 requires a methodical approach, utilizing a digital multimeter (DMM) and an OBD-II scanner:

1. Visual Inspection: Begin with a thorough visual inspection of the rear wiper motor, its associated wiring harness, and the rear wiper motor run relay. Pay close attention to areas where wiring flexes, such as the tailgate hinge or chassis pass-throughs, looking for signs of chafing, fraying, pinch points, corrosion, or water intrusion. Inspect the relay and motor connectors for bent pins, corrosion, or looseness. Check the relevant fuses in the vehicle’s fuse box for the rear wiper circuit. A blown fuse indicates a direct short and should be replaced, but be aware it may blow again until the underlying short is resolved.
2. OBD-II Scan and Live Data: Connect an OBD-II scanner to confirm the presence of B1245. Check for any other related or pending DTCs that might provide additional clues. If available, monitor live data parameters related to the rear wiper system, such as wiper switch input status, relay command status, and actual voltage feedback from the wiper circuit. This can help identify if the BCM is commanding the relay off but still detecting voltage.
3. Rear Wiper Motor Run Relay Test:
   • Locate the rear wiper motor run relay. With the ignition off, carefully remove the relay from its socket.
   • Using a DMM set to continuity mode, check for continuity between the load side terminals (typically pins 30 and 87) on the relay itself. There should be no continuity when the relay is de-energized. If continuity exists, the relay is internally shorted or stuck closed and needs replacement.
   • Next, apply fused 12V power and ground from the vehicle battery to the relay’s coil terminals (typically pins 85 and 86). You should hear an audible “click,” indicating the coil is activating. While activated, re-test for continuity between pins 30 and 87. Continuity should now be present. If not, the relay is faulty.
4. Relay Socket Voltage Testing: With the relay removed from its socket, turn the ignition to the “ON” position (engine off). Use a DMM to measure voltage at the relay socket terminals:
   • Terminal 30 (Power Input): Should show constant battery voltage (approx. 12V).
   • Terminal 87 (Load Output to Motor): This is the critical terminal for B1245. When the wiper system is off and the relay is removed, this terminal should show close to 0V. If it shows battery voltage, there is a short to battery positive further down the circuit between the relay socket and the wiper motor, or a backfeed from another circuit.
   • Terminal 86 (Coil Power): This terminal typically receives battery voltage when the BCM/GEM commands the relay ON. Measure voltage here with the wiper switch toggled.
   • Terminal 85 (Coil Ground/Control): This terminal is typically controlled by the BCM/GEM, providing a ground signal to energize the relay coil. Measure voltage here with the wiper switch toggled.
5. Wiring Continuity and Short Circuit Testing: Disconnect the vehicle battery to prevent further shorts or damage. Isolate the affected wire in the circuit (e.g., the wire from relay terminal 87 to the rear wiper motor). Use a DMM to check for continuity between this isolated wire and a known good constant 12V power source (e.g., another fused 12V wire in the vehicle that is known to be hot at all times) with the battery disconnected. There should be no continuity. If continuity is present, trace the wire meticulously to locate the exact point of the short to battery. Repeat this process for the relay control wires (85 and 86) if suspicions point to a short on the control side.

Recommended Repairs and Solutions

Once the root cause of B1245 has been identified through systematic diagnosis, the appropriate repairs can be performed:

• Replace the Rear Wiper Motor Run Relay: If diagnostic tests confirm the relay is internally faulty (stuck closed, shorted, or non-responsive), replacing it with a new, OEM-quality relay is the primary solution. This is often the most common and straightforward fix.
• Repair or Replace Damaged Wiring: If a short to battery is identified within the wiring harness, the damaged section must be repaired or replaced. For localized damage (e.g., chafing), carefully cut out the compromised section, solder in a new wire of the same gauge, and protect the repair with heat-shrink tubing and electrical tape. Ensure any repairs are routed away from sharp edges or moving parts to prevent recurrence. If the damage is extensive, consider replacing the entire harness section.
• Clean or Replace Corroded Connectors: If corrosion is found on the relay socket or motor connectors, use electrical contact cleaner and a small brush to thoroughly clean the terminals. If the corrosion has caused significant damage to the terminals (e.g., pitting, deformation), the connector shell and individual pins should be replaced. Apply dielectric grease to the terminals to prevent future corrosion.
• Replace the Rear Wiper Motor: If, after exhaustive testing of the relay and wiring, the fault is isolated to an internal short or severe electrical issue within the rear wiper motor itself that is causing the “short to battery” condition on the relay circuit, then the rear wiper motor assembly will need replacement.
• Replace the BCM/GEM: This is a measure of last resort. Only consider replacing the BCM/GEM if all other components (relay, wiring, motor) have been meticulously tested and confirmed to be in good working order, and diagnostic procedures unequivocally point to an internal module failure. BCM replacement typically requires specialized programming and calibration with a factory-level diagnostic tool.

After performing any repairs, clear the DTCs from the BCM/GEM using an OBD-II scanner and thoroughly test the rear wiper system through all its modes of operation to ensure the fault has been rectified and the system functions correctly.