P1338 — Fuel Pump Module Communication Failure

What does P1338 specifically mean?

P1338 indicates a malfunction in the communication circuit between the fuel pump control module and the controller that commands it, preventing proper confirmation or control of fuel-pump operation.

Can the vehicle be driven with P1338?

Driving with P1338 is not recommended for extended periods because incorrect pump control may cause hesitation, rough running, fuel starvation, or an engine stall while moving.

What are the most common causes of P1338?

Common P1338 causes include damaged wiring, corroded connectors, an open or shorted communication line, unstable module power or ground, or a defective fuel pump control module.

How should P1338 be diagnosed before parts are replaced?

Confirm P1338 with an OBD scanner, inspect both module connectors and the harness, verify power and ground, and test the communication signal. Module replacement should follow circuit testing rather than the code alone.

When your vehicle's powertrain control module detects a fault in a sensor or actuator circuit that persists across multiple ignition cycles, it logs trouble code P1338. This code represents a specific electrical problem within one of the many control circuits your engine management system relies on. Unlike codes triggered by a single anomaly, P1338 requires the PCM to verify the fault condition repeatedly under defined operating parameters before activating the Check Engine light on your dashboard.

The onboard diagnostic system monitors voltage, resistance, and signal integrity throughout your vehicle's sensor and actuator network. When readings fall outside acceptable ranges—due to wiring issues, connector problems, or component failures—the PCM logs P1338 along with a freeze frame snapshot. That snapshot captures engine load, RPM, coolant temperature, and vehicle speed at the exact moment the fault occurred, giving you precise conditions to replicate during diagnosis.

Symptoms of P1338

The Check Engine light illumination is typically the first sign you've developed code P1338. Beyond that warning lamp, you may notice the affected system operating erratically or not functioning at all. Depending on which specific circuit is compromised, your vehicle could enter a reduced-power limp mode designed to protect drivetrain components. Some drivers report elevated fuel consumption when P1338 is active, as the engine management system compensates for inaccurate sensor data. In severe cases, related safety systems may flag warnings on your instrument cluster.

Common Causes

Wiring problems account for the majority of P1338 occurrences. An open circuit—meaning a broken or disconnected wire—or a short to ground or power prevents proper signal transmission between the PCM and the affected component. Corrosion at electrical connectors creates high resistance, disrupting data flow and triggering this code. Loose connector pins produce similar symptoms through intermittent contact. Poor ground connections prevent components from completing their electrical circuits correctly, leading to voltage irregularities the PCM interprets as faults. A blown fuse in the affected circuit's power supply also generates this code.

How to Diagnose P1338

Begin by connecting a quality OBD2 scanner to your vehicle's diagnostic port and retrieve all stored codes along with their corresponding freeze frame data. Document the conditions recorded when P1338 first appeared, including engine temperature, RPM, load percentage, and vehicle speed. Next, research technical service bulletins specific to your make, model, and year—manufacturers often publish known issues and software updates addressing these fault codes. Perform a thorough visual inspection of the wiring harness and connectors associated with the suspected circuit, looking for damaged insulation, broken strands, corrosion buildup, or any signs of moisture intrusion. Using a multimeter, check for proper reference voltage and ground at the component connector while comparing readings to manufacturer specifications. Finally, conduct a wiggle test on the harness while monitoring live data streams on your scanner; any signal dropouts indicate intermittent wiring failures that require repair.

Repair Options and Costs

Address the most common and affordable causes before considering component replacement. Wiring harness repairs or connector replacements typically run between $80 and $250 for parts and professional labor. If inspection reveals a faulty sensor or actuator at the end of the circuit, expect to pay $150 to $500 depending on the specific part and your vehicle's make. In rare situations where the PCM itself requires repair or replacement, costs climb to the $300 to $1,000 range. The total cost to fix P1338 usually falls between $80 and $1,000 depending on root cause. An accurate diagnosis before purchasing parts prevents unnecessary expenses—always eliminate wiring and connector issues before replacing expensive control modules.

Driving Safety Assessment

Most vehicles remain drivable when P1338 is stored, though you may experience diminished performance or notice certain auxiliary systems becoming unavailable. Monitor your dashboard closely for additional warning lights, particularly those indicating stalling conditions, starting failures, or brake/steering concerns. If such symptoms develop, discontinue driving and address the issue promptly rather than risking further complications.

Related OBD2 Codes

• P1300: Multi-faults - Bank 1 - With Low Side Shorts
• P1301: Multi-faults - Bank 2 - With Low Side Shorts
• P1302: Injector High Sides Shorted Together
• P1303: IDM Failure
• P1304: Cylinder Head Overtemperature Protection Active
• P1305: Boost Calibration Fault