What is OBD2 Code P1479 on a Dodge?
OBD2 diagnostic trouble code P1479 is a manufacturer-specific code primarily associated with Chrysler, Dodge, and Jeep vehicles. Its generic definition is “Leak Detection Pump Switch or Circuit.” This code is directly related to the vehicle’s Evaporative Emission Control (EVAP) system, a critical component for reducing hydrocarbon emissions and preventing fuel vapors from escaping into the atmosphere. When the Powertrain Control Module (PCM) detects an electrical fault within the Leak Detection Pump’s (LDP) switch circuit—such as an open, short to ground, or short to voltage—it will illuminate the Check Engine Light and store code P1479. Unlike codes for large leaks (P0455) or small leaks (P0456), P1479 points to an electrical or functional failure of the pump’s internal switch used during the system’s self-test.
Symptoms and Common Causes of P1479
Identifying the symptoms and root causes is the first step in effective troubleshooting. A P1479 code often presents subtly but can lead to a failed emissions test.
Primary Symptoms of Code P1479
- Illuminated Check Engine Light (MIL): The most common and often the only noticeable symptom.
- Failed EVAP System Monitor: The vehicle’s onboard diagnostics will be unable to complete the EVAP system self-test, which is required for emissions readiness.
- Possible Fuel Odor: While not always present, a compromised Leak Detection Pump can sometimes lead to a faint smell of gasoline near the vehicle.
- No Driveability Issues: Crucially, engine performance, fuel economy, and drivability are typically unaffected by this code alone.
Most Frequent Causes of P1479
- Faulty Leak Detection Pump (LDP): The internal switch or motor within the pump itself has failed. This is the most common culprit.
- Damaged Wiring or Connectors: Corroded, broken, or shorted wires in the LDP circuit, especially near the pump (often located near the fuel tank).
- Poor Electrical Connections: A loose or oxidized connector at the Leak Detection Pump or the PCM.
- Blown Fuse: A fuse supplying power to the LDP or the EVAP system solenoid control circuit.
- Rarely, a Faulty PCM: An internal failure of the Powertrain Control Module is possible but should be considered only after all other causes are ruled out.
Step-by-Step Diagnostic and Repair Guide
Diagnosing P1479 requires a systematic approach, starting with the simplest checks. You will need a quality OBD2 scanner, a digital multimeter (DMM), and basic hand tools.
Step 1: Preliminary Inspection and Code Verification
Begin with a thorough visual inspection. Locate the Leak Detection Pump (common on many Dodge/Jeep models near the spare tire or fuel tank). Check its electrical connector for corrosion, bent pins, or looseness. Follow the wiring harness from the pump, looking for chafing, cuts, or burn marks. Clear the code with your scanner, perform a drive cycle, and see if P1479 returns immediately or after the EVAP monitor runs. An immediate return suggests a hard fault.
Step 2: Electrical Circuit Testing
Using a wiring diagram for your specific model is highly recommended. With the connector disconnected from the LDP and the ignition OFF, use your multimeter to check for continuity between the suspected ground wire and chassis ground. Next, with the ignition ON, check for reference voltage (typically 5V or 12V) at the appropriate pin. Check for short-to-power or short-to-ground in the signal wire back to the PCM. Any readings outside specification indicate a wiring fault that must be repaired.
Step 3: Testing the Leak Detection Pump Itself
Resistance checks can often determine pump health. Consult a service manual for the exact specifications for your vehicle’s LDP. Typically, you will measure the resistance across the pump motor terminals and across the switch terminals. An open circuit (infinite resistance) or a short (zero or very low resistance) indicates an internal failure of the pump. Some advanced scanners can also command the LDP on and off for an operational test.
Step 4: Repair and Clearance
Based on your findings:
- Repair Wiring: Solder and seal any repaired wires, and ensure connectors are clean and tight.
- Replace the LDP: If the pump fails electrical tests, replacement is necessary. Use an OEM or high-quality aftermarket part.
- Address Fuses/Connections: Replace any blown fuses and ensure all connections are secure.
After the repair, clear all codes. The critical final step is to perform a complete drive cycle to allow the PCM to run all monitors, especially the EVAP monitor, to ensure the code does not return and the system is “Ready” for emissions testing.
Vehicle-Specific Notes and Importance of Repair
Common Dodge, Chrysler, and Jeep Models Affected
Code P1479 is prevalent across many FCA (Stellantis) vehicles from the late 1990s through the 2010s. Common models include the Dodge Ram 1500/2500, Dodge Durango, Dodge Charger, Dodge Challenger, Jeep Grand Cherokee, Jeep Liberty, Chrysler 300, and Chrysler Town & Country. The diagnostic process is similar, but the physical location of the Leak Detection Pump may vary.
Why You Should Not Ignore Code P1479
While your vehicle may run fine, ignoring P1479 has consequences. First, you will fail any state or local emissions inspection, as the EVAP monitor will be in a “Not Ready” state. Second, a malfunctioning EVAP system can allow harmful fuel vapors to pollute the air. Third, what starts as an electrical fault (P1479) could be related to or mask an actual physical vapor leak, potentially leading to a lingering fuel smell. Addressing P1479 promptly restores your vehicle’s full emissions compliance and ensures all systems are functioning as designed.