Code
B3718
HUMMER
B — Body
Front Wiper Relay Drive Circuit High (BCM)
Views:
UK: 12
EN: 27
RU: 17
AI status
Completed
Completed
100%
Causes
- Short to battery voltage on the front wiper relay control wire
- Stuck or welded relay contacts feeding back voltage into the driver
- Corroded or damaged relay connector or harness causing intermittent high voltage
- BCM driver transistor or internal BCM failure
- Poor or missing ground elsewhere in the circuit causing abnormal voltages
- Aftermarket equipment or modifications backfeeding the circuit
Symptoms
- Wipers run intermittently or continuously without driver input
- Wipers inoperative or stuck in park position
- BCM-related faults or lamp on the instrument cluster
- Intermittent wiper operation or loss of control
- Possible blown fuse(s) related to wiper circuit
What to check
- Retrieve freeze frame data and full DTC list with a scan tool; record conditions when code set
- Inspect front wiper relay and socket for corrosion, melted plastic or signs of overheating
- Verify fuses and accessory power feeds for the wiper circuit
- Visually inspect wiring harness from relay to wiper motor and BCM for damage, pinched wires or aftermarket taps
- Verify good battery voltage and chassis/engine grounds
Signal parameters
- BCM output (wiper relay drive) expected when OFF: near 0 V (typically
- BCM output when ON: switched to battery voltage (≈11–14 V)
- Relay coil supply (constant feed) typically battery voltage (≈11–14 V)
- Typical relay coil current draw (varies by relay): roughly 0.1–1.0 A depending on coil resistance
Diagnostic algorithm
- Connect a scan tool, confirm B3718 is current or history and note freeze-frame conditions. Clear the code and attempt to reproduce.
- With ignition ON (wipers OFF), measure voltage at the BCM relay driver pin/wire at the relay socket. Expected: low (~0 V). If high (~battery), verify whether feed is being backfed from the relay feed circuit.
- Remove the front wiper relay. Re-measure the BCM driver pin at the harness with relay removed. If voltage returns low with relay removed, suspect the relay or feed wiring backfeed. If still high with relay removed, suspect wiring short to battery or BCM fault.
- Inspect and wiggle the harness and connector while monitoring the driver voltage for intermittent faults. Repair any damaged wiring or corroded terminals.
- Check continuity between BCM driver pin and relay socket; check for unintended continuity to battery feed or other circuits. Repair shorts/splices as needed.
- Swap the relay with a known-good relay of the same type (if available) to rule out relay internal failure.
- Verify ground integrity for the wiper motor and BCM ground points.
- If wiring and relay verify good and the driver output still shows a high fault condition, suspect BCM internal driver failure. Verify by following manufacturer procedures for BCM bench tests or replacement qualification before replacing the BCM.
- After repairs, clear codes and verify proper operation through multiple cycles (intermittent, low/high speed, park position).
Likely causes
- Shorted wiring between relay socket and power source (relay control wire tied to battery)
- Failed front wiper relay with internal short or welded contacts
- Corrosion or wiring chafing at relay connector or splice
- Faulty BCM output driver on the front wiper relay circuit
Fault status
Status
BCM detected a voltage on the front wiper relay drive circuit higher than the allowed threshold. Possible causes include a short to battery, a stuck/failed relay, wiring/connector damage, or an internal BCM driver fault.
Repair difficulty: Medium
Diagnostic time: 0.5 - 2.0 hours
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