System: Body | Standard: ISO/SAE Controlled | Fault type: Circuit Low
Definition source: SAE J2012 naming/structure guidance
What Does B3722 Mean?
B3722 – Rear Wiper Relay Drive Circuit Low (BCM) is an ISO/SAE controlled diagnostic trouble code in the Body system. It indicates the Body Control Module (BCM) has detected a circuit low condition in the rear wiper relay drive circuit.
In practical terms, the BCM commands the rear wiper by driving the relay control (drive) circuit. When the BCM expects that drive circuit voltage/state to be within a certain range and instead detects it is lower than expected, it sets B3722. A “circuit low” result typically points to an electrical condition that is pulling the control circuit toward ground or preventing the circuit from reaching its commanded level.
This code is about the relay drive/control side (the BCM’s output and the relay coil/control circuit), not automatically the wiper blade, linkage, or motor itself—though downstream faults can sometimes contribute by changing circuit loading.
Quick Reference
- Code: B3722
- Official Title: Rear Wiper Relay Drive Circuit Low (BCM)
- System: Body
- Standard classification: ISO/SAE Controlled
- Fault type: Circuit Low
- Primary module involved: BCM
- What it affects: Rear wiper relay control/command circuit; rear wiper operation may be limited or inoperative
Symptoms
- Rear wiper inoperative: rear wiper does not run when commanded
- Intermittent rear wiper operation: works sometimes, fails at other times
- Rear wiper stops unexpectedly: may stop during a wipe cycle or fail to continue running
- Rear washer wipe function inconsistent: washer request may not be followed by expected rear wipe behavior (if equipped/configured that way)
- Warning indicator/message or stored code: B3722 stored in the BCM (visible with a scan tool capable of body codes)
Common Causes
- Rear wiper relay drive/control circuit short to ground: the BCM output or control wire is pulled low
- High resistance in the relay drive circuit: damaged wiring, corrosion, or poor terminal contact causing abnormal voltage drop and a low reading
- Connector or terminal issues: loose, spread, backed-out, contaminated, or corroded terminals at the BCM connector, relay socket, or an in-line connector
- Rear wiper relay fault: relay coil internal fault (including coil short) that overloads the BCM driver and drags the circuit low
- Power/ground integrity problems affecting circuit behavior: related fuse/feed/ground issues that alter expected circuit operation depending on the vehicle’s circuit design
- BCM driver/output fault: BCM internal driver unable to properly command or monitor the rear wiper relay drive circuit
Diagnosis Steps
Use a scan tool that can access BCM codes and data, a digital multimeter, and the correct wiring diagram for the specific vehicle configuration. Follow service information precautions for probing connectors and for keeping modules asleep when performing resistance checks.
- Confirm the code and its context. Scan all modules, record B3722 as stored/pending/current, and note any related body or power management codes. Save freeze frame/failure records if available.
- Verify the symptom. Command the rear wiper using the switch or a scan tool output test (if supported). Confirm whether the rear wiper is inoperative, intermittent, or stops unexpectedly.
- Check fuses and relay identification. Using the wiring diagram, identify the correct rear wiper relay and related fuses/feeds. Verify fuses are intact and seated properly.
- Inspect the relay and relay socket. Look for heat discoloration, corrosion, moisture, damaged terminals, or signs the relay is not fully seated.
- Inspect wiring and connectors in the control path. Focus on the BCM connector(s), any in-line connectors, and the harness routing to the rear body area. Look for pinched wiring, chafing, or water intrusion. Repair any obvious physical damage before deeper testing.
- Command the rear wiper and measure the control circuit. At the relay control/coil terminal (per wiring diagram), backprobe and measure voltage/state while commanding ON and OFF. A circuit that remains low when it should be driven indicates a short-to-ground, excessive load, or a driver issue.
- Isolate the relay load. Remove the rear wiper relay and repeat the control-circuit measurement while commanding ON/OFF:
- If the control circuit returns to normal behavior with the relay removed, suspect a relay coil fault or an issue that causes the relay control side to be overloaded.
- If it remains low with the relay removed, suspect wiring short-to-ground, connector/terminal faults, or a BCM driver issue.
- Check for short-to-ground (power off, modules asleep). With the system powered down per service info, test the relay drive/control wire for unintended continuity to ground. A low resistance path suggests a short-to-ground or moisture contamination.
- Check end-to-end continuity and voltage drop. Verify continuity from the BCM output pin to the relay control terminal. If continuity is present, perform voltage drop testing under commanded operation to identify excessive resistance at connectors, splices, or terminals.
- Confirm relay coil integrity (bench test if appropriate). If service information supports it, verify the relay coil is not shorted and operates correctly. Replace the relay if it fails specification or causes the control circuit to pull low.
- Evaluate BCM output only after circuit checks. If wiring, terminals, and relay test good and the circuit still shows a low condition when commanded, follow OEM procedures for BCM output driver diagnosis before considering module repair/replacement.
- Clear and verify. Clear codes, operate the rear wiper through multiple cycles, and re-scan to confirm B3722 does not return.
Need wiper wiring diagrams and relay-circuit test steps?
Wiper and washer faults often require relay socket checks, BCM output testing, switch-input checks, and front/rear body harness diagnosis.
Possible Fixes
- Repair wiring damage in the rear wiper relay drive/control circuit (short-to-ground, open, or high resistance)
- Clean and restore connector/terminal integrity at the BCM connector, relay socket, and any in-line connectors (repair terminal fit/tension as required)
- Replace the rear wiper relay if testing confirms a coil fault or abnormal loading that pulls the drive circuit low
- Restore proper power/ground integrity for related feeds/grounds per wiring diagram and service information
- Diagnose and repair BCM output driver concerns only after confirming the external circuit and relay are not responsible
Can I Still Drive With B3722?
You can typically drive with B3722 because it is a Body system code related to the rear wiper relay drive circuit, not a powertrain or braking control fault. The primary concern is reduced rear visibility if the rear wiper is inoperative or intermittent during rain, snow, or spray.
If the rear wiper behaves unpredictably, avoid relying on it until the circuit low condition is diagnosed and repaired, since an electrical fault in the control circuit can worsen or create additional electrical issues in the same harness area.
Repair Costs
Repair cost depends on whether the confirmed root cause is wiring, connector condition, a switch or module issue, or the labor needed to diagnose the fault correctly.
| Repair Type | Estimated Cost |
|---|---|
| Basic DIY inspection | FAQ– |
| Professional diagnosis | 0 – 0 |
| Wiring / connector repair | – 0+ |
| Component / module repair | 0 – 0+ |
FAQ
Is B3722 a BCM code?
Yes. The official title includes “(BCM)” and the code indicates the Body Control Module detected a rear wiper relay drive circuit low condition.
What does “circuit low” mean for B3722?
“Circuit low” means the BCM measured the rear wiper relay drive/control circuit at a lower voltage/state than expected during monitoring. This can happen if the circuit is pulled toward ground, overloaded, or has a resistance/connection problem that prevents the circuit from reaching the commanded level.
Will a bad relay cause B3722?
It can. A rear wiper relay with a coil fault (including a shorted coil) can overload the BCM’s driver and contribute to a circuit low condition, triggering B3722.
What should I check first for B3722?
Start with the basics tied directly to the code: confirm the correct rear wiper relay and related fuses, then inspect the relay socket and the BCM-to-relay control wiring for damage, corrosion, or poor terminal fit. After that, measure the relay drive circuit while commanding the rear wiper ON/OFF.
Does B3722 automatically mean the rear wiper motor is bad?
No. B3722 specifically points to a rear wiper relay drive circuit low detected by the BCM. While other faults can influence circuit behavior, the code itself targets the relay control/drive circuit and its electrical integrity.