B1338 — Door Ajar RR Circuit Short To Ground

What is the most common cause of B1338?

The most common causes are: faulty switch, motor or actuator of the affected system, blown fuse or failed relay, damaged wiring in door jambs or wet areas.

How much does it cost to fix B1338?

Repair wiring or connectors — $80–$250; Replace the switch or actuator — $120–$450; BCM repair or replacement — $300–$900. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

How do I diagnose B1338 myself?

Start with a scan: confirm B1338, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the body electrical system, and verify the suspect component against live data before buying parts.

Will B1338 clear itself?

Sometimes B1338 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

Is it safe to drive with B1338?

Usually safe to drive — body codes rarely affect drivability. Exceptions: exterior lighting and wipers in bad weather, and central locking faults that can leave the car unsecured.

When your vehicle's control module logs code B1338, it's reporting a specific electrical problem in the body system — a short to ground on the right rear door ajar circuit. In plain language: the module expected a normal signal from that circuit but instead detected an unintended path to ground. This usually means a wire has lost its insulation and is touching bare metal, a connector has become waterlogged, or an internal switch failure is pulling the circuit to ground when it shouldn't.

The right rear door ajar switch is the component at the center of this issue. Its job is straightforward — tell the body control module whether the door is open or closed. That signal feeds several functions: interior lighting, the dome light delay feature, and the security alarm system. When B1338 sets, the module receives an abnormal reading it cannot interpret correctly, so it stores the fault and illuminates the check engine or body system warning light.

The module does not set B1338 after a single glitch. It typically monitors the circuit across multiple drive cycles and confirms the fault persists before committing the code. Along with the stored trouble code, the module saves a freeze frame snapshot — engine rpm, load, coolant temperature, and vehicle speed recorded the instant the failure occurred. That data is gold during diagnosis because it tells you exactly what conditions triggered B1338 in the first place.

Symptoms of B1338

• The body system or check engine warning light stays illuminated on the dashboard
• Interior dome light fails to turn on when the right rear door opens, or stays on when the door closes
• Central locking may behave unpredictably, since the module cannot determine the correct door position
• Security system malfunctions if your vehicle uses door position inputs for arming or disarming
• In most cases, engine performance and drivability remain unaffected — the vehicle still runs and drives normally
• The affected door may incorrectly display as open or closed on the instrument cluster

Common causes of B1338

The most frequent culprit is a faulty door ajar switch itself — these small plastic components sit inside the door latch and wear out over time, developing internal shorts. Second most common: damaged wiring inside the right rear door jamb. Door wiring harnesses flex thousands of times as doors open and close, and the insulation eventually cracks, especially in areas where the door meets the body. Water intrusion accelerates both problems — moisture in connectors creates corrosion that conducts stray current to ground. Corroded or loose electrical connectors anywhere in the door ajar circuit will produce the same result. A failed body control module is less common but still possible if voltage spikes or water damage have compromised its internal circuits. Blown fuses or failed relays supplying the door circuit can also trigger B1338, though this is relatively rare.

How to diagnose B1338

1. Connect an OBD2 scanner and confirm B1338 is stored. Record the freeze frame data immediately — it shows engine conditions at the exact moment the fault appeared.
2. Check for any related trouble codes. Secondary codes often point to the underlying cause rather than the consequence. Search for TSBs (technical service bulletins) for your specific make, model, and year — manufacturers publish service fixes for recurring B0xxx code patterns that can save hours of diagnosis.
3. Perform a visual inspection of the right rear door ajar switch and its wiring harness. Look for cracked insulation, exposed copper strands, moisture residue, or greenish corrosion on terminals.
4. Monitor the door switch PID in live data while manually opening and closing the right rear door. The signal should toggle cleanly between open and closed states — any hesitation or partial readings indicate a worn switch or bad connection.
5. Inspect connectors at flex points, particularly the door hinge area where wires bend repeatedly. Wiggle the harness gently while watching live data for intermittent dropouts.
6. Clear B1338, complete a full drive cycle that replicates the conditions captured in the freeze frame, and verify the code does not return.

Repair options and costs

Begin with the least expensive repairs before replacing major components. Wiring harness repair or connector replacement typically runs $80–$250 for parts and labor at an independent shop. If diagnostics confirm the door ajar switch is faulty, replacement costs $120–$450 depending on the vehicle and whether the switch is integrated into the door latch assembly or sold separately. In cases where the body control module itself has failed, BCM repair or replacement ranges from $300–$900.

Total repair cost for B1338 generally falls between $80 and $900 depending on the root cause. An accurate diagnosis before purchasing parts is strongly recommended — the most expensive scenario (BCM replacement) should never be the first assumption.

Can you drive with B1338?

In most vehicles, B1338 presents minimal safety risk — body electrical codes do not typically affect engine operation, transmission function, or braking systems. The vehicle remains driveable, and you will not cause additional damage by continuing to drive short distances. However, if the malfunction involves exterior lighting, wipers during inclement weather, or a central locking system that leaves the vehicle unsecured, those exceptions warrant more urgent attention. Overall, B1338 is classified as short-term safe to drive, but the underlying issue should be diagnosed and repaired at the earliest convenience.

Related OBD2 codes

• B1300: Power Door Lock Circuit Failure
• B1301: Power Door Lock Circuit Open
• B1302: Accessory Delay Relay Coil Circuit Failure
• B1303: Accessory Delay Relay Coil Circuit Open
• B1304: Accessory Delay Relay Coil Circuit Short To Battery
• B1305: Accessory Delay Relay Coil Circuit Short To Ground