B3708 – Front Washer Motor Input High (BCM)

System: Body | Standard: ISO/SAE Controlled | Fault type: General

Definition source: SAE J2012 naming/structure guidance (verify exact wording against your official DTC dataset)

B3708 means the vehicle’s body control module (BCM) is seeing an abnormally high input signal related to the front windshield washer motor circuit. For most drivers, this can show up as the front washer not spraying when commanded, the washers running at the wrong time, or washer operation that seems inconsistent—making it harder to keep the windshield clear in rain, slush, or road salt. Technically, “input high” indicates the BCM is reading a higher-than-expected electrical state on the front washer motor input circuit, which can be caused by wiring, connector, switch, motor, or BCM input issues rather than one confirmed failed part.

The B3708 code points to a “high” electrical reading on the BCM’s front washer motor input circuit. Start by checking the washer motor connector, related wiring/grounds, and the washer switch/input signal before replacing any parts.

What Does B3708 Mean?

The meaning of B3708 is that the BCM detected the front washer motor input signal higher than it expects during a self-check or while the washers were requested. In plain terms, the module thinks the washer-motor-related input is stuck “too high,” which can prevent normal washer operation or cause unexpected behavior. In technical terms, “Input High” is a circuit-signal fault category: the BCM is measuring a high voltage/state on the monitored input line associated with the front washer motor control/feedback path (exact design varies by make/model), so the code identifies a suspected trouble area in the body electrical system—not a confirmed bad washer motor.

Theory of Operation

Under normal operation, the driver commands the front washers using a stalk switch or multifunction switch. The BCM interprets that request and then controls the front washer motor (often through an internal driver, an external relay, or a smart power stage depending on vehicle design). The washer pump motor runs, fluid sprays, and the BCM expects the related input circuit to change state in a plausible way when the command is present and return to normal when the command ends.

With B3708, the BCM is detecting that the front washer motor input circuit remains higher than expected (or is higher than expected at an invalid time). This can happen if a signal line is shorted to power, a connector is contaminated bridging terminals, a harness is damaged, an internal switch/contact is biased high, or a module input/driver is not behaving correctly. Because architectures vary, confirming the exact “input” being monitored requires using the vehicle wiring diagram and checking the BCM data list for washer request/washer output status while testing the circuit.

Symptoms

You will usually notice washer system problems first, but some vehicles may only store the B3708 diagnostic code with minimal symptoms.

• Front washers inoperative: pressing the washer command results in no pump/motor operation and no spray
• Washers run unexpectedly: the washer motor may run without a washer request or run longer than intended
• Intermittent washer function: washer operation works sometimes, then fails, especially after rain, washing the vehicle, or temperature changes
• Washer warning/message: a body system warning message or service notification may appear (depending on cluster/software)
• Wiper/washer behavior odd: wipers may not perform the normal “courtesy wipes” or timing linked to washer activation on some vehicles
• Nozzle spray weak or inconsistent: pump may not run at full duty (if the system disables/limits operation due to the detected input fault)
• Multiple body codes stored: related BCM codes may accompany B3708 when a shared power/ground or connector is affected

Common Causes

• Cause: Short to battery voltage or another powered circuit on the front washer motor input circuit (signal stays higher than expected)
• Cause: Corroded, loose, pushed-out, or water-intruded connector at the washer pump/motor, BCM, or an inline junction causing an unintended high reading
• Cause: Wiring harness damage (chafing/pinched insulation) near the washer reservoir, radiator support, hood hinge area, or fender liners allowing cross-feed voltage
• Cause: Front washer motor/pump internal electrical fault creating abnormal feedback/input behavior (possible, not guaranteed)
• Cause: Poor ground path for the washer motor circuit (shared ground point loose/corroded), which can skew the BCM’s interpreted input level
• Cause: Incorrect fuse/relay installation, aftermarket wiring, or accessory tie-ins that backfeed voltage into the washer motor input circuit
• Cause: BCM input stage or internal circuit fault (rare; consider only after power/ground/wiring checks pass)
• Cause: Network/configuration or calibration issue affecting BCM interpretation of the washer input (less common; verify service info/updates after electrical integrity is confirmed)

Diagnosis Steps

Use a capable scan tool that can read Body/BCM DTCs and live data, a digital multimeter, and the correct wiring diagram for your exact vehicle. A fused jumper wire and a test light can help load-test circuits safely. Because B3708 is a BCM “input high” fault, focus on signal integrity, connector condition, and backfeed/short-to-power checks before condemning modules.

1. Confirm DTC B3708 is current (active) or history, and record freeze-frame/body event data if available (vehicle state, washer command, battery voltage).
2. Check for related body electrical codes and address power supply or communication codes first; multiple BCM codes can point to a shared power/ground issue.
3. Verify the customer complaint: operate the front washers and observe whether the pump runs, whether it runs continuously, or whether it does nothing.
4. Perform a visual inspection at the washer reservoir/pump area: look for water intrusion, damaged loom, rubbed-through insulation, and loose or broken connector locks.
5. Inspect the washer pump/motor connector terminals closely for green corrosion, spread terminals, or evidence of overheating; repair terminal fit issues before further testing.
6. Using the wiring diagram, identify the BCM “front washer motor input” circuit and backprobe at the BCM and/or pump connector; check whether the input stays high when the system is not commanded.
7. Key on, washer not requested: measure the suspected input circuit for unexpected voltage. If voltage is present when it should not be, isolate by unplugging the pump/motor and then the BCM connector (as service info allows) to see when the high voltage disappears.
8. Check for short-to-power/cross-feed: with connectors unplugged as appropriate, perform continuity tests between the input circuit and known power circuits; inspect nearby harness routing points where chafing commonly occurs.
9. Load-test grounds and power feeds used by the washer circuit (and any shared ground points). A circuit can look fine unloaded but fail under load, causing the BCM to misread the input.
10. If the scan tool supports it, monitor BCM data PIDs related to front washer request/input while commanding washers (via switch or bi-directional control). Compare PID changes to actual circuit measurements to catch intermittent connector faults.
11. After repairing any wiring/connector issues, clear codes and perform multiple washer activation cycles, including a short road test if needed, to confirm B3708 does not reset.

Professional tip: “Input high” faults are often caused by backfed voltage from a rubbed harness or water-filled connector. If B3708 returns immediately after clearing, prioritize unplug-and-isolate testing to determine whether the high signal is coming from the harness side, the load (pump/motor), or the BCM input.

Possible Fixes

• Repair chafed wiring or shorts-to-power on the front washer motor input circuit; re-route and re-protect the harness to prevent repeat damage
• Clean, dry, and secure connectors; replace corroded terminals, seals, or connector bodies where water intrusion is found
• Restore proper ground integrity by cleaning/tightening shared ground points and repairing damaged ground wires
• Replace the front washer pump/motor if testing shows it is contributing to abnormal input behavior (only after verifying wiring and command circuits)
• Correct aftermarket wiring/accessory backfeeds and verify proper fuses/relays are installed per the wiring diagram
• Reflash, repair, or replace the BCM only if the input circuit tests normal end-to-end and the BCM still detects an unjustified high input

Can I Still Drive With B3708?

In most cases you can still drive with the B3708 code stored, because it’s a Body (BCM) fault related to the front washer motor input signal being detected as “high,” not an engine or brake control failure. The practical risk is reduced visibility: the front windshield washer may not work correctly (or may behave unpredictably), which can become a safety issue in rain, road spray, mud, or winter conditions. If the washer is inoperative, avoid driving in conditions where you can’t keep the windshield clear and schedule diagnosis soon.

How Serious Is This Code?

B3708 is usually a moderate-severity fault: it’s often an inconvenience when the washer system doesn’t respond, runs at the wrong time, or the warning/message appears, but the vehicle typically remains drivable. It becomes more serious when the front washer function is lost and visibility is compromised (night driving, highway spray, snow/slush), or if the underlying electrical issue causes repeated fuse failures, battery drain, or affects other BCM-controlled Body functions. Treat it as “fix soon,” and “fix now” if you can’t maintain safe windshield visibility.

Repair Costs

Last updated: March 22, 2026