B1817 — Wiper Rear Motor Down Relay Coil Circuit Short To Ground #

Note: The wording for this DTC may vary depending on the vehicle manufacturer (OEM). Below are some known variations:

• B1817 – Rear Wiper Motor Down Relay Circuit Short to Ground (Ford, Mazda)
• B1817 – Rear Wiper Down Relay Coil Shorted to Ground (Chrysler, Dodge)
• B1817 – Rear Wiper Relay Circuit Low (Nissan, Infiniti)

Summary of B1817 #

The B1817 code indicates that the vehicle’s onboard diagnostic system has detected an electrical short to ground in the relay coil circuit responsible for moving the rear wiper motor to its “down” or rest position. In simpler terms, this means that somewhere in the wiring or relay, electricity is unintentionally flowing directly to the vehicle’s chassis (the “ground”), potentially preventing the wiper from operating correctly. Modern vehicles use relays as electronically controlled switches to manage the power sent to high-draw components like wiper motors. When this circuit is compromised, it can result in erratic or non-functional rear wiper operations. While this is rarely a safety-critical fault, it can be inconvenient—especially in poor weather conditions. Prompt diagnosis and repair are recommended to restore normal functionality.

Common Symptoms for Code B1817 #

When the B1817 code is present, you may notice several telltale signs related to your rear wiper system. Some symptoms are obvious, while others may be more subtle. Be attentive to the following:

• The rear wiper does not move or parks incorrectly
• Wiper only works intermittently, or at limited speeds
• Unusual clicking sounds near the rear wiper motor or relay
• Rear wiper stops in the middle of its sweep
• Dashboard warning lights related to the wiper system may illuminate
• Possible blown fuse for the rear wiper circuit

Probable Causes for Code B1817 #

There are several potential reasons why the B1817 code might be triggered. Some are more common than others, and understanding these helps target your diagnostic efforts effectively. Here are the most frequent causes, in order of likelihood:

1. Wiring harness damage—Chafed, pinched, or corroded wires shorting to the vehicle body
2. Faulty relay—Internal short within the rear wiper down relay coil
3. Connector issues—Loose, bent, or corroded pins at the relay or wiper motor
4. Rear wiper motor fault—Motor windings shorting to ground, though less common
5. Water intrusion—Moisture in the rear hatch area damaging electrical components
6. Incorrect aftermarket modifications—Poorly installed wiring or accessories affecting the circuit

Step-by-Step Diagnostic Guide for B1817 #

Diagnosing B1817 requires a methodical approach to avoid unnecessary part replacements and ensure an accurate fix. Follow these steps:

• Verify the code with a reliable OBD-II/EOBD scanner and clear it, then see if it returns.
• Visually inspect the wiring harness between the rear wiper motor, relay, and vehicle body for any signs of wear, corrosion, or damage.
• Check all related connectors for water, corrosion, or bent pins; clean or repair as needed.
• Test the relay by swapping it with a known-good identical relay (if possible).
• Measure the resistance of the relay coil circuit using a multimeter. A reading close to zero indicates a short to ground.
• Inspect the rear wiper motor for internal shorts (unplug the motor and check for continuity between the coil and vehicle ground).
• Review the vehicle’s wiring diagram for any shared circuits and check for other affected systems.
• After repairs, clear the code and verify normal rear wiper operation.

Possible Repairs for B1817 #

Once the root cause of the B1817 code has been identified, the following repairs are commonly performed. Always address the underlying issue—don’t just clear the code:

• Repair or replace damaged wiring harness sections
• Replace the faulty rear wiper down relay
• Clean and secure connector terminals and pins; replace if corroded or broken
• Replace rear wiper motor if found shorted to ground
• Seal or repair areas where water is entering and affecting components
• Remove or correct any incorrect aftermarket electrical modifications

Can You Drive With Code B1817? #

Yes, but with limitations. The B1817 code does not typically impact the core safety or drivability of your vehicle, as it relates solely to the rear wiper system. However, if you rely on your rear wiper for visibility—especially in rain or snow—driving without it can be hazardous. It’s best to address the issue sooner rather than later, particularly if you live in an area with frequent inclement weather.

Vehicles Most Affected by B1817 #

While B1817 can appear in various makes and models, it is more commonly reported in vehicles where the rear wiper wiring is routed through moving tailgates or hatchbacks, increasing the risk of wire fatigue or water ingress. The following vehicles are frequently associated with this code:

• Ford Escape/Kuga (2012–2019)
• Mazda CX-5, CX-7 (2010–2017)
• Dodge Caravan and Chrysler Town & Country (2008–2016)
• Nissan Rogue/X-Trail (2014–2021)
• Jeep Grand Cherokee (2011–2019)

Common Mistakes & Best Practices for B1817 #

Misdiagnosing a B1817 code can lead to unnecessary expenses or recurring issues. Here’s what to avoid and how to approach the repair process:

• Replacing the wiper motor before checking the relay and wiring
• Overlooking connector corrosion, especially after exposure to moisture
• Neglecting to check for blown fuses or shared circuit issues
• Ignoring potential aftermarket wiring changes
• Always use OEM or high-quality replacement parts to ensure reliability
• After repair, verify function in all rear wiper modes before returning the vehicle to service

FAQ Express – B1817 #

Still have questions? Here are answers to some of the most common concerns about B1817:

• Q: Can I reset the B1817 code myself?
  A: You can clear the code with an OBD-II scanner, but if the root problem isn’t fixed, it will likely return almost immediately.
• Q: Does B1817 mean I need a new rear wiper motor?
  A: Not always. Most often, the issue is with the relay or wiring rather than the motor itself. A thorough diagnosis is essential before replacing parts.