B1240 — Wiper Washer Rear Pump Relay Circuit Failure #

The code label may vary depending on the vehicle manufacturer (OEM). Below are known description variations for this DTC:

• Rear Washer Pump Relay Circuit Malfunction (Ford)
• Rear Wiper Washer Pump Relay Open/Short (Toyota)
• Rear Washer Relay Circuit Fault (Nissan)

Summary of code B1240 #

B1240 is an OBD-II (On-Board Diagnostics) body code that signals a problem with the electrical circuit controlling the rear wiper washer pump relay. In simpler terms, this means the vehicle’s control module (often called the Body Control Module, or BCM) has detected an abnormality—such as an open or short circuit—within the wiring, relay, or related components that activate the rear window washer pump. This code is often triggered when the system cannot properly energize the pump relay or detect correct feedback, which is essential for spraying washer fluid on the rear glass. The code does not directly indicate the pump itself is faulty, but rather the relay circuit that powers it. Identifying and addressing this issue is important for both convenience and safety, especially when rear visibility is compromised.

Common symptoms for code B1240 #

When B1240 is present, you may notice several operational issues related to the rear wiper washer system. These problems tend to be obvious, but can sometimes go unnoticed until you need to clean your rear window. Watch for the following:

• Rear washer pump does not operate (no fluid sprays when activated)
• Intermittent or weak washer fluid spray
• Rear wiper works, but no washer fluid dispenses
• Warning light or message on the dashboard (in some vehicles)
• Clicking noise from rear relay area, but no pump action

Likely causes for B1240 (in order of frequency) #

The B1240 code generally points to faults within the rear washer pump relay circuit. The most common culprits are electrical in nature, but mechanical failure is possible. Here’s what typically triggers this code, starting with the most frequent:

1. Faulty rear washer pump relay (sticking contacts or internal failure)
2. Wiring issues (open circuit, short to ground, corroded connections)
3. Blown fuse (protecting the rear washer circuit)
4. Defective rear washer pump (drawing excessive current or open coil)
5. Body Control Module (BCM) malfunction (rare, but possible if controls the relay directly)

Step-by-step diagnosis for B1240 #

Diagnosing B1240 requires a systematic approach to avoid unnecessary part replacements. Always follow basic safety procedures and consult your vehicle’s wiring diagram if possible. Here’s a proven step-by-step checklist:

• 1. Scan for additional codes: Check for related DTCs that could help pinpoint a shared wiring or module issue.
• 2. Inspect the fuse: Locate and visually check the fuse for the rear washer pump circuit. Replace if blown and re-test.
• 3. Test the relay: Remove the rear washer pump relay and bench-test it with a 12V source, or swap with an identical known-good relay.
• 4. Check wiring and connectors: Inspect the wiring harness and connectors at the relay, pump, and BCM for corrosion, loose pins, or damage.
• 5. Measure voltage and ground: With a multimeter, verify battery voltage is present at relay terminals when commanded and that ground connections are solid.
• 6. Test the rear washer pump: Apply direct battery voltage to the pump terminals (with relay out) to verify pump operation and current draw.
• 7. Evaluate BCM output: If all above checks pass, determine if the BCM is providing the correct control signal to the relay.

Possible repairs for B1240 #

Once the specific cause is found, the following repairs are typical for resolving B1240. Always address the root cause, not just the symptom, to prevent recurrence.

• Replace the faulty rear washer pump relay
• Repair or replace damaged wiring/connectors in the relay circuit
• Replace a blown fuse and address underlying cause (such as a shorted pump)
• Install a new rear washer pump if it is drawing excessive current or has an open coil
• Reprogram or replace the BCM (only if confirmed defective and after all other steps)

Is it safe to drive with code B1240? #

Yes, you can generally continue driving with code B1240 present, but with some limitations. This code does not affect critical engine or braking functions; however, your rear visibility may be reduced in poor weather or dirty conditions since the rear washer will not operate as designed. For safety, it is always advisable to repair washer system issues promptly—especially if you rely on clear rear vision.

Vehicles most commonly affected by B1240 #

While B1240 can appear on various makes, it’s more commonly reported on certain vehicles, especially those with dedicated rear washer pump relays and BCM-controlled circuits. The following vehicles are among those most frequently associated with this code:

• Ford Escape, Explorer, Focus
• Toyota RAV4, Highlander
• Nissan Rogue, Murano
• Mazda CX-5, CX-9
• Chevrolet Equinox, Traverse

Common mistakes & best practices for B1240 #

Avoiding misdiagnosis and unnecessary parts replacement is key with B1240. Here are some common errors, and the best ways to proceed:

• Replacing the washer pump without testing the relay or circuit first
• Overlooking a blown fuse or corroded connector
• Failing to verify ground connections
• Assuming BCM failure before checking all wiring and relay components
• Best practice: Always use a wiring diagram and test each circuit component systematically before replacing any parts.

Quick FAQ about code B1240 #

Q: Will clearing the code fix the issue?
A: No. Clearing the code may turn the warning light off temporarily, but if the underlying fault remains, B1240 will return the next time the system self-tests.

Q: Can a stuck rear washer pump cause B1240?
A: Yes. If the pump is internally shorted or draws excessive current, it can blow the fuse or damage the relay, causing the code to set.