Understanding the Dodge P1485 Diagnostic Trouble Code
The OBD2 diagnostic trouble code (DTC) P1485 is a manufacturer-specific code primarily associated with Dodge, Chrysler, Jeep, and Ram vehicles. In simple terms, it indicates a malfunction within the circuit of the Evaporative Emission (EVAP) Leak Detection Pump (LDP) or Leak Monitor Pump. This system is a critical component of your vehicle’s emissions control, designed to prevent fuel vapors from escaping into the atmosphere. When the Powertrain Control Module (PCM) detects an electrical fault—such as an open, short, or performance issue—in the LDP’s control circuit, it stores code P1485 and illuminates the check engine light. Ignoring this code can lead to failed emissions tests and, in some cases, driveability issues.
What is the EVAP Leak Detection Pump (LDP)?
The Leak Detection Pump is not a traditional fuel pump. It is an electrically-operated pump used by many Chrysler group vehicles to pressurize the EVAP system for leak testing. During a self-test (usually performed after a cold start under specific driving conditions), the PCM activates the LDP. The pump creates a slight vacuum or pressure in the fuel tank and vapor lines. The PCM then monitors pressure changes to determine if the system is sealed or has a leak exceeding a specified size (e.g., 0.020″ or 0.040″). A fault in its control circuit prevents this crucial self-test from completing.
How the PCM Detects a P1485 Fault
The PCM monitors the LDP circuit by sending a pulsed signal and checking for expected feedback. It looks for proper voltage levels and electrical current draw. If the signal is absent, out of range, or indicates an unexpected resistance (like an open or short to ground/power), the PCM interprets this as a circuit malfunction and triggers P1485. This is a “Circuit” code, meaning the problem is electrical in nature, not necessarily a mechanical failure of the pump itself.
Common Symptoms of a P1485 Code on Your Dodge
While sometimes the only symptom is an illuminated check engine light (MIL), a persistent P1485 code can manifest in other noticeable ways. Recognizing these signs can help you understand the urgency of the repair.
Primary Symptom: Check Engine Light
The most universal and immediate symptom is the illumination of the malfunction indicator lamp (MIL) on your dashboard. A code scanner will confirm the presence of P1485. It may be the only code stored or appear alongside related EVAP codes like P0442 (small leak) or P0455 (large leak) if the circuit fault prevents leak testing.
Potential Performance and Operational Symptoms
- Failed Emissions Inspection: This is a very common consequence. Since the EVAP monitor cannot run, your vehicle’s onboard diagnostics will show an “incomplete” or “not ready” status for the EVAP test, causing an automatic failure in regions with mandatory testing.
- Fuel Odor: While less common with a pure circuit fault, if the LDP is stuck or a related valve is compromised, you might smell gasoline vapors near the vehicle, especially after refueling.
- Rough Idle or Hard Starting: In rare cases, a severe vacuum leak caused by a stuck-open component in the EVAP system (related to the LDP’s failure) can introduce unmetered air, leading to a rough idle or extended cranking.
Diagnosing the Root Cause of P1485
Effective diagnosis requires a methodical approach, starting with the simplest checks. You will need a quality digital multimeter (DMM) and a wiring diagram for your specific Dodge model.
Step 1: Preliminary Visual and Basic Checks
- Locate the LDP: Typically found near the fuel tank or in the rear quarter panel. On many Dodge trucks and SUVs, it’s behind a protective panel near the spare tire.
- Inspect Wiring and Connectors: Look for obvious damage, corrosion, chafed wires, or loose connections at the LDP harness connector. Check the connector pins for bent or pushed-out terminals.
- Check Related Fuses: Consult your owner’s manual to find and inspect the fuse for the EVAP system or PCM. A blown fuse is a quick fix but indicates a deeper short circuit.
Step 2: Electrical Circuit Testing with a Multimeter
This is the core of the diagnosis. Disconnect the electrical connector from the LDP.
- Test for Power (Supply Voltage): With the ignition key in the ON position, probe the appropriate wire (often a red/white or orange wire) for battery voltage (approx. 12V). No voltage points to an open circuit or fuse issue.
- Test for Ground: Check the ground wire (often black) for continuity to a good chassis ground. High resistance indicates a bad ground connection.
- Test the LDP Solenoid Coil: Use the multimeter’s ohmmeter function across the two terminals of the pump itself (not the vehicle harness). Resistance should typically be between 10 and 30 ohms. A reading of infinite ohms (open) or zero ohms (short) confirms a failed pump.
- Check for Shorts to Ground/Power: Test each wire in the vehicle harness for a short to ground or to power with the connector still disconnected.
Step 3: Functional Test and PCM Considerations
If the wiring and pump resistance check out, you can command the LDP with a capable bidirectional scan tool. If the tool can activate the pump and you hear/feel it click, the circuit is functional, and the issue may be an intermittent fault or a failing PCM (rare). A lack of activation with good power and ground suggests a PCM driver circuit failure.
Repair Solutions for the P1485 Code
Once the faulty component is identified, the repair is typically straightforward. Always clear the codes after repair and perform a drive cycle to ensure the monitor runs and the code does not return.
Repair 1: Fixing Wiring Harness Issues
If the problem is damaged wiring, repair it using proper solder and heat shrink tubing—never use twist connectors. Ensure the repair is sealed from moisture. Clean corroded connector terminals with electrical contact cleaner.
Repair 2: Replacing the Leak Detection Pump (LDP)
This is the most common fix. If the pump’s coil resistance is out of specification or it fails the activation test, replacement is necessary.
- Ensure the vehicle is cool and parked on a level surface.
- Disconnect the negative battery cable as a safety precaution.
- Disconnect the electrical connector and the vacuum hoses (note their positions!).
- Unbolt or unclip the old pump, install the new one, and reconnect everything.
- Use OEM or high-quality aftermarket parts for reliability.
Repair 3: Addressing a Blown Fuse or Bad Ground
Replace a blown fuse with one of the identical amperage rating. If it blows again, you have a short circuit that must be found. Clean and tighten ground connections, sanding down to bare metal if needed to ensure a perfect connection.
Professional Insight and Final Recommendations
While P1485 is generally not a code that will strand you on the side of the road, it is important to address it promptly. A non-functional EVAP leak test means you cannot know if your fuel system is properly sealed, potentially releasing pollutants and wasting fuel through evaporation.
Cost Estimation for Repair
Costs vary widely. A DIY repair with a pump costing $80-$150 is the most economical. At a repair shop, including diagnosis and labor, expect a total bill between $200 and $400, depending on labor rates and the vehicle’s accessibility.
Importance of a Complete Drive Cycle
After clearing the code, the vehicle must complete a specific drive cycle to run the EVAP monitor. This often involves driving on the highway for a sustained period after a cold start with a fuel tank level between 15% and 85%. Only after a successful test will the monitor show “ready,” allowing you to pass an emissions inspection.
By following this structured diagnostic approach, you can effectively resolve the P1485 code on your Dodge, restoring full emissions system functionality and turning off that check engine light for good.