Understand & Fix P2402: EVAP System Leak Detection Pump Control Circuit High with iCarsoft CR Ultra P

If your vehicle’s check engine light illuminates and you fail an emissions test, a diagnostic scan will likely return P2402. This OBD-II code stands for "Evaporative Emission (EVAP) System Leak Detection Pump Control Circuit High"—a critical fault indicating the Engine Control Module (ECM) has detected an abnormal high voltage in the EVAP leak detection pump’s control circuit. The EVAP system captures fuel vapors to prevent environmental pollution; a faulty control circuit disrupts leak detection, leading to emissions non-compliance and potential performance issues.

Basic scanners might only flag an "EVAP system error" but can’t test circuit voltage, pump responsiveness, or wiring integrity—leaving you guessing between a faulty pump, damaged wiring, or ECM malfunction. The iCarsoft CR Ultra P, with its OE-level EVAP diagnostics, bi-directional control, and circuit testing tools, solves this. Below, we break down P2402, its causes, symptoms, step-by-step resolution, and 8 FAQs to answer common troubleshooting questions.

What Is P2402?

P2402 targets the EVAP system’s leak detection pump (LDP) control circuit. The LDP pressurizes the EVAP system to check for leaks; the ECM controls the pump via a voltage signal (typically 5V or 12V). The code triggers when the ECM detects a voltage reading higher than the expected range (e.g., 12V when 5V is required) in the control circuit, indicating a short, open, or faulty component.

Key Symptoms of P2402

• Illuminated Check Engine Light: The primary indicator, often paired with codes like P2401 (circuit low) or P0442 (small EVAP leak).
• Failed Emissions Tests: Disrupted EVAP leak detection leads to excess fuel vapor emissions, violating test standards.
• Fuel Odor: Uncaptured fuel vapors may escape, creating a noticeable gasoline smell near the vehicle.
• Reduced Fuel Economy: A malfunctioning EVAP system can disrupt fuel vapor recirculation, wasting fuel.
• LDP Failure: The leak detection pump may not activate, preventing the ECM from verifying system integrity.

Common Causes of P2402

Why iCarsoft CR Ultra P Excels at Diagnosing P2402

The CR Ultra P outperforms basic tools with features tailored to EVAP system and circuit diagnostics:

Step-by-Step: Diagnose P2402 with iCarsoft CR Ultra P

1. Confirm P2402 & Gather Data

   Plug the CR Ultra P into the OBD-II port, power on, and select AutoVIN Identify to retrieve your vehicle’s specs.
   Navigate to Engine > Fault Codes > Read Codes to confirm P2402. Tap Code Details for insights (e.g., "Toyota Camry: EVAP LDP Control Circuit High; Voltage: 12.5V, Expected: 4.5–5.5V; Check Wiring or LDP").

2. Analyze Live Circuit Voltage Data

   Go to Engine > Live Data > EVAP System and monitor two key metrics:
   1. LDP Control Circuit Voltage: Should match OEM specs (e.g., 5V at idle). A constant high reading (12V+) confirms the fault.
   2. LDP Activation Status: The ECM should activate the pump during leak tests. No activation = circuit or pump issue.

3. Test the Leak Detection Pump (LDP)

   1. Use Bi-Directional Control > EVAP System > LDP Test: Send activation commands to the LDP. Listen for a humming sound (pump running) and check voltage changes. No response = faulty LDP.
   2. Locate the LDP: Use the CR Ultra P’s Component Location tool (typically near the fuel tank or rear bumper).
   3. Inspect & Test: Check for damage/corrosion. Use the CR Ultra P’s Resistance Test to verify pump windings (should match specs, e.g., 10–20 ohms).

4. Inspect Wiring, Fuses & Relays

   1. Wiring Check: Use Continuity Test to check LDP wiring for breaks. Look for frayed wires or corrosion near connectors.
   2. Fuse/Relay Check: Navigate to Vehicle > Fuse Box Diagram (via CR Ultra P) to locate EVAP-related fuses/relays. Test continuity with the tool’s multimeter.
   3. Short Circuit Test: Set to "Voltage" mode, probe the circuit with ignition on—no short = voltage matches specs.

5. Repair & Clear the Code

   - Replace the LDP if tests fail (use OEM-compatible parts).
   - Repair damaged wiring, replace blown fuses/relays, or clean corroded connectors as needed.
   - Use the CR Ultra P to Clear Codes and run an EVAP Leak Detection Test (under Special Functions) to confirm P2402 is resolved.

FAQs: P2402 Troubleshooting

• Can I drive with P2402?
  Yes, but you’ll fail emissions tests, and prolonged driving may damage the EVAP system or ECM. Use the CR Ultra P to monitor circuit voltage—if it stays consistently high, repair promptly.
• How much does it cost to fix P2402?
  A new leak detection pump costs $100–$300, plus $150–$250 for labor. Using the CR Ultra P to diagnose yourself saves on shop diagnostic fees ($100–$150).
• Why does P2402 keep returning after clearing it?
  The root cause wasn’t fixed. Common culprits: unaddressed wiring shorts, a faulty relay, or a damaged ECM. Use the CR Ultra P’s History Log to track recurrence (e.g., after rain = water-damaged wiring).
• Is P2402 caused by a loose gas cap?
  No—a loose gas cap triggers P0442 (small leak), not P2402. P2402 is strictly a control circuit issue, not a physical leak.
• How do I distinguish between a faulty LDP and wiring?
  Use bi-directional testing: LDP doesn’t activate + high circuit voltage = faulty LDP; LDP activates but voltage remains high = wiring short to power.
• Do I need to reset the EVAP system after repair?
  Yes—use the CR Ultra P’s EVAP System Reset (under Special Functions) to clear adaptive data and ensure the ECM recognizes the repaired circuit.
• Can a dead battery cause P2402?
  Indirectly—low battery voltage disrupts ECM signal output, leading to false high-voltage readings. Use the CR Ultra P’s Battery Tester to check voltage (12.4–12.7V is normal).
• Will P2402 affect fuel economy?
  Yes—a malfunctioning EVAP system can’t recirculate fuel vapors, increasing fuel consumption by 5–10%. Fixing P2402 restores efficient vapor recirculation.