Understanding OBD2 Code P1473: The EVAP System Sentinel
When your vehicle’s check engine light illuminates and a diagnostic scan reveals the OBD2 code P1473, it points directly to a fault within a critical component of your car’s emission control system. Specifically, P1473 is defined as “Leak Detection Pump Circuit High”. This code is manufacturer-specific but is commonly found in Chrysler, Dodge, Jeep, and other Stellantis vehicles. The Leak Detection Pump (LDP) is the heart of the EVAP (Evaporative Emission Control) system’s self-diagnostic routine. Unlike generic EVAP codes, P1473 indicates an electrical or performance issue with the pump circuit itself, preventing the system from accurately testing for fuel vapor leaks. Ignoring this code can lead to failed emissions tests and potentially allow harmful hydrocarbons to escape into the atmosphere.
Root Causes and Symptoms of a P1473 Diagnostic Trouble Code
A P1473 code is set when the vehicle’s Powertrain Control Module (PCM) detects an abnormal voltage signal or an implausible condition in the Leak Detection Pump circuit. This is typically during the key-on engine-off (KOEO) test or during a driving cycle. The “Circuit High” designation usually means the PCM is seeing a voltage higher than expected, often pointing to an open circuit or a failing component.
Primary Causes of the P1473 Fault
- Faulty Leak Detection Pump (LDP): The most common culprit. Internal motor failure, seized pump, or internal electrical faults within the LDP assembly.
- Open or Shorted Wiring: Damaged, corroded, or broken wires in the LDP control circuit or its power feed. This includes poor connections at the pump connector or the PCM.
- Blown Fuse: A dedicated fuse for the LDP circuit may be blown, cutting power to the pump entirely.
- Failed EVAP System Solenoid or Valve: While less direct, a stuck-open vent solenoid or a faulty purge valve can cause abnormal pressure readings that confuse the LDP diagnostic.
- Defective Powertrain Control Module (PCM): A rare but possible cause where the PCM itself fails to provide the correct signal or interpret feedback from the LDP.
Common Symptoms Drivers Experience
- Illuminated Check Engine Light (MIL): The primary and often only initial symptom.
- Failed Emissions Inspection: The vehicle will not pass a state or local emissions test with an active P1473 code.
- Possible Fuel Odor: While not always present, a compromised EVAP system can sometimes lead to a smell of gasoline, especially near the fuel tank or under the hood.
- No Direct Driveability Issues: The car will typically run, start, and drive normally, as this is an emissions-related fault, not a fuel or ignition problem.
Step-by-Step Diagnosis and Repair for Code P1473
Diagnosing a P1473 code requires a methodical approach, combining visual inspection, electrical testing, and functional checks. Always begin with the simplest and most cost-effective steps. You will need a digital multimeter (DMM) and a reliable scan tool capable of accessing manufacturer-specific data.
Step 1: Preliminary Visual Inspection
Locate the Leak Detection Pump. It is usually found in the engine bay or near the fuel tank. Carefully inspect:
- The LDP electrical connector for corrosion, bent pins, or looseness.
- The wiring harness leading to the pump for any obvious chafing, cuts, or burn damage.
- The vacuum lines connected to the LDP for cracks, disconnections, or brittleness.
- The relevant fuse in the power distribution center (check your owner’s manual for location).
Step 2: Electrical Circuit Testing
With the battery disconnected, use your multimeter to perform continuity and resistance checks.
- Power and Ground: Check for battery voltage (typically 12V) at the appropriate pin of the LDP connector with the key in the ON position. Verify a clean ground path.
- Signal Circuit: Test the resistance of the control circuit wire from the LDP connector back to the PCM connector for an open or short.
- Pump Resistance: Unplug the LDP and measure its internal motor resistance across its terminals. Compare the reading to the manufacturer’s specification (often between 10-30 ohms). An infinite reading (open) or zero reading (short) confirms a bad pump.
Step 3: Functional and Data Stream Analysis
Using your advanced scan tool, command the LDP to activate. You should hear and feel a distinct clicking or humming from the pump. If it’s silent, it’s likely faulty or not receiving power. Monitor the EVAP system test data, such as LDP duty cycle and system pressure, to see if the PCM is attempting to command the pump and if it’s responding.
Step 4: Component Replacement and Code Clearance
Once the faulty component is identified (most often the LDP itself), proceed with replacement.
- Disconnect the battery.
- Disconnect the electrical connector and vacuum lines, noting their positions.
- Remove the mounting bolts and the old pump.
- Install the new Leak Detection Pump, reconnect all lines and the electrical connector securely.
- Reconnect the battery, clear the P1473 code with your scan tool, and perform a complete drive cycle to allow the PCM to run its self-tests and verify the repair.
Technical Insights and Prevention Strategies
The Leak Detection Pump operates by applying a precise vacuum to the sealed EVAP system and then monitoring the rate of decay. A “Circuit High” fault disrupts this calibration. Technicians often find that LDP failure is accelerated by moisture ingress or exposure to extreme underhood temperatures.
Why Timely Repair of P1473 is Crucial
- Emissions Compliance: A functional EVAP system is legally required to minimize environmental pollution.
- Preventing Secondary Issues: A stuck LDP or related solenoid can sometimes affect fuel tank pressure, potentially leading to difficult refueling (gas pump clicking off prematurely).
- Diagnostic Clarity: An unresolved P1473 can mask or complicate the diagnosis of other, smaller EVAP leak codes (like P0442).
Proactive Maintenance Tips
- During routine underhood inspections, visually check the condition of the LDP and its connections.
- Always ensure the gas cap is tightened securely after refueling to maintain proper EVAP system integrity.
- Address any other EVAP-related codes immediately, as system strain can contribute to LDP failure.
While a P1473 code may not strand you on the side of the road, it is a clear call to action for your vehicle’s emission health. A systematic diagnosis will pinpoint the issue, whether it’s a simple wiring repair or a pump replacement, restoring your EVAP system to full function and ensuring your vehicle runs cleanly and efficiently.