What Does B1816 Mean?
This code indicates that the Body Control Module (BCM) has detected a short-to-battery voltage condition in the rear wiper motor down relay coil circuit. The control module sensed unexpected battery voltage present on the relay coil control wire when it should have been at ground or off state. This prevents proper control of the rear wiper motor down function and can cause the rear wiper to operate continuously or not at all.
Common Causes
45%
Damaged or chafed wiring harness causing short to power between BCM and rear wiper relay
30%
Faulty rear wiper motor down relay with internal short to battery
15%
Corroded or damaged connector pins at BCM or relay causing cross-circuit short
10%
Failed Body Control Module with internal short on relay driver circuit
Diagnostic Steps
1
Step 1: Perform visual inspection of rear wiper relay, connector, and all associated wiring from BCM to relay location. Look for chafed, pinched, or damaged wires, corroded terminals, or signs of water intrusion.
2
Step 2: Disconnect the rear wiper motor down relay and use a digital multimeter to check for battery voltage on the relay coil control wire from the BCM (should read 0V with relay removed and ignition on). If battery voltage is present, there is a short in the wiring harness.
3
Step 3: With relay still disconnected, check resistance of the relay coil (typically 70-100 ohms). Also check for continuity between relay coil terminals and relay case/ground to identify internal relay short.
4
Step 4: If wiring and relay test good, disconnect BCM connector and inspect pins for corrosion, damage, or pushed-back terminals. Measure resistance between the relay control circuit and battery voltage circuit at BCM connector (should be infinite resistance/open circuit).
5
Step 5: If all wiring and connections are intact, suspect BCM internal fault. Replace BCM or relay as identified by previous tests, clear codes, and verify proper rear wiper operation through all modes.
Estimated Repair Cost
$100 - $600
Parts + labor, varies by vehicle and location
This code indicates that the Body Control Module (BCM) has detected a short-to-battery voltage condition in the rear wiper motor down relay coil circuit. The control module sensed unexpected battery voltage present on the relay coil control wire when it should have been at ground or off state. This ...
The most common cause of B1816 (Wiper Rear Motor Down Relay Coil Circuit Short To Battery) is: Damaged or chafed wiring harness causing short to power between BCM and rear wiper relay
Typical repair costs for B1816 range from $100 to $600, 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 visibility cleaning function. Repair at convenience, though reduced rear visibility in inclement weather may be a concern for larger vehicles where rear visibility is important.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1816 to identify the root cause.
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Quick Info
Category
Body
System
Rear Wiper/Washer System
Difficulty
Type
Manufacturer
Recommended Tools
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