What Does B1817 Mean?
This code indicates that the Body Control Module (BCM) has detected an abnormal short-to-ground condition in the control circuit for the rear wiper motor down relay coil. The BCM monitors the relay coil circuit and sets this code when it detects current flow to ground that exceeds normal parameters, suggesting the control wire is directly grounded or the relay coil itself is internally shorted. This prevents proper operation of the rear wiper motor in the down or park position.
Common Causes
45%
Damaged or chafed wiring in the rear wiper relay coil control circuit creating a direct short to ground, often near body/hinge points
30%
Failed rear wiper motor down relay with internally shorted coil winding to ground
15%
Corroded or moisture-damaged connector terminals at relay socket or BCM creating ground path
10%
Failed Body Control Module with internal driver circuit short to ground
Diagnostic Steps
1
Step 1: Visually inspect the rear wiper motor down relay location and identify the relay. Remove the relay from its socket and inspect both relay terminals and socket for corrosion, burning, or moisture damage. Check relay coil resistance with multimeter between coil terminals (should read 70-90 ohms typically); if reading near 0 ohms, relay coil is shorted.
2
Step 2: With relay removed, use multimeter to measure resistance from the BCM-side relay coil control terminal in the socket to ground. Reading should be infinite (open circuit). If resistance is low (under 10 ohms), the control circuit is shorted to ground.
3
Step 3: Inspect wiring harness from relay socket back to BCM, paying special attention to areas where harness passes through grommets, near hinges, or contact points with body panels. Look for chafed, pinched, or damaged wire insulation. Flex harness while monitoring resistance to find intermittent shorts.
4
Step 4: If wiring and relay test normal, disconnect BCM connector and measure resistance from relay control circuit pin at BCM connector to ground with relay removed. Infinite resistance confirms wiring is good; low resistance indicates wiring fault. Near-zero resistance with BCM disconnected confirms external short; if short only appears with BCM connected, BCM internal fault is likely.
5
Step 5: Repair or replace identified shorted wiring, damaged connectors, or faulty relay. Clear codes and cycle rear wiper operation through all modes to verify relay energizes properly and code does not return. Confirm BCM can control relay without setting fault.
Estimated Repair Cost
$100 - $450
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) has detected an abnormal short-to-ground condition in the control circuit for the rear wiper motor down relay coil. The BCM monitors the relay coil circuit and sets this code when it detects current flow to ground that exceeds normal parameters,...
The most common cause of B1817 (Wiper Rear Motor Down Relay Coil Circuit Short To Ground) is: Damaged or chafed wiring in the rear wiper relay coil control circuit creating a direct short to ground, often near body/hinge points
Typical repair costs for B1817 range from $100 to $450, 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 wiper functionality. Reduced rear visibility in inclement weather creates minor safety concern, but repair is not urgent unless rear visibility is legally required or weather conditions demand it.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1817 to identify the root cause.
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Quick Info
Category
Body
System
Rear Wiper System
Difficulty
Type
Manufacturer
Recommended Tools
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