What Does B1240 Mean?
This code indicates the Body Control Module (BCM) has detected an electrical fault in the rear wiper washer pump relay circuit. The BCM monitors the control circuit for proper voltage and ground, and has identified either an open circuit, short circuit, excessive resistance, or relay failure. This prevents the rear washer pump from operating when commanded by the driver.
Common Causes
35%
Failed rear washer pump relay with internal contact corrosion or coil failure
30%
Damaged wiring or corroded connectors between BCM and relay, often from water intrusion or chafing
20%
Faulty rear washer pump motor causing excessive current draw and relay circuit protection
10%
Blown fuse or fusible link in the relay power supply circuit
5%
Failed BCM internal relay driver circuit
Diagnostic Steps
1
Step 1: Locate the rear wiper washer pump relay (typically in main fuse/relay box or auxiliary box) and visually inspect for signs of burning, corrosion, or damage. Check relay socket for corrosion, loose pins, or water intrusion.
2
Step 2: With ignition off, remove relay and check fuse integrity. Use multimeter to test relay coil resistance (typically 70-120 ohms) and verify relay switching operation using 12V power supply and observing contact closure with ohmmeter.
3
Step 3: With relay removed and ignition on, command rear washer activation (or back-probe BCM connector if accessible). Use multimeter to verify BCM provides 12V switching signal to relay coil terminal. Check relay power supply terminal for constant 12V from fuse.
4
Step 4: Disconnect rear washer pump connector and measure pump motor resistance (typically 2-5 ohms). Check for short to ground. Reconnect pump and measure current draw during operation (should be 3-6 amps typically).
5
Step 5: Inspect wiring harness from BCM to relay and relay to pump for chafing, pinch points, or water damage. Pay special attention to rear hatch hinge areas and wire grommets where movement can cause wear.
6
Step 6: After repair, clear codes and verify operation of rear washer system multiple times. Monitor live data for relay command signal and verify no codes return after several wash cycles.
Estimated Repair Cost
$75 - $400
Parts + labor, varies by vehicle and location
This code indicates the Body Control Module (BCM) has detected an electrical fault in the rear wiper washer pump relay circuit. The BCM monitors the control circuit for proper voltage and ground, and has identified either an open circuit, short circuit, excessive resistance, or relay failure. This p...
The most common cause of B1240 (Wiper Washer Rear Pump Relay Circuit Failure) is: Failed rear washer pump relay with internal contact corrosion or coil failure
Typical repair costs for B1240 range from $75 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to continue driving as this only affects rear window cleaning capability. Repair at convenience, though reduced rear visibility during inclement weather may impact safe driving conditions in rain or snow.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1240 to identify the root cause.
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Quick Info
Category
Body
System
Body Electrical System - Rear Wiper/Washer
Difficulty
Type
Manufacturer
Recommended Tools
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