B1817: Rear Wiper Park Relay Circuit Short to Ground
The B1817 diagnostic trouble code indicates that the control module (typically the GEM or BCM) has detected a short to ground in the rear wiper park/return relay coil circuit. This circuit controls the relay responsible for completing the wiper sweep cycle and returning the wiper arm to its rest position. A short to ground prevents proper relay activation or causes excessive current draw, which the module identifies as a fault. To protect components, the module disables the function and stores the code.
1. Commonly Affected Makes
2. Most Common Causes
- Short to ground in the wiring of the rear wiper relay coil control circuit
- Internally shorted relay coil (if the relay is a replaceable external component)
- Internal damage to the control module (GEM/BCM) driver or relay control circuit
- Corroded, bent, or moisture-damaged relay or module connectors/pins causing a short to ground
- Blown fuse in the circuit as a result of the short (requires wiring repair first)
3. Symptoms You Will Notice
- Rear wiper does not park or return to the rest position
- Rear wiper may be inoperative or function intermittently
4. Step-by-Step Diagnosis
Check for blown fuse related to the rear wiper system; replace if necessary after repairing the short.
Inspect the rear wiper relay and its socket for corrosion, damage, or moisture.
Test the relay coil resistance; compare to specifications (typically 50-100 ohms).
Check for continuity to ground on the relay control wire from the module; if continuity exists, repair the short.
If wiring and relay are good, suspect a faulty GEM/BCM and perform module diagnostics.
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but the rear wiper may not function or park correctly. Avoid using the rear wiper until repaired to prevent further electrical damage.
How much does it cost to fix?▼
Repair costs typically range from $100 to $400, depending on whether the issue is a simple wiring repair, relay replacement, or module replacement.