P2402 Code: That Cold-Start Rattle Is the EVAP Pump, Not a Leak

What Does P2402 Actually Mean?

Modern vehicles use an Evaporative Emission Control (EVAP) system to prevent fuel vapors from escaping into the atmosphere. The system stores vapors in a charcoal canister and periodically routes them into the engine to burn. To make sure the system is sealed (no vapor escape), the PCM runs an automated leak test — typically about 5 hours after the engine is shut off — using a small electric pump called the Leak Detection Pump (LDP), sometimes called the Canister Pump Module on Chrysler/Jeep platforms.

P2402 fires when the PCM detects that the LDP's electrical control circuit is reading higher voltage or current than expected. Translation: the pump is drawing too much power, is stuck in the ON position, or has shorted internally. The pump's job is to test for leaks — but in P2402 cases, the pump itself is the broken part, not whatever it was trying to test.

What Are the Symptoms of P2402?

P2402's symptoms are mostly silent — it doesn't affect engine performance or driveability. But it does have one famous audible giveaway:

Is P2402 Code Serious?

Low severity for driveability, but guaranteed emissions test failure. P2402 won't strand you, won't damage your engine, and won't compromise safety. But it has consequences:

The good news: P2402 is one of the cheapest "serious-looking" codes to fix. The pump is usually accessible without complex disassembly, the part is moderately priced, and the diagnostic process is fast with the right tools. You're rarely looking at more than a single afternoon of DIY work.

What Causes a P2402 Code? (Ranked by Frequency)

P2402's cause distribution is unusual for an OBD-II code — the pump itself dominates, with little variance across platforms.

What You'll Need

How Do You Fix a P2402 Code?

Follow these steps in order. The cold-start rattle test (Step 2) and bidirectional pump test (Step 3) confirm the cause for free, in under 5 minutes combined.

• 1

  Scan for All Codes and Locate the Leak Detection Pump

  Plug in your scanner and record every stored code. P2402 frequently appears with companion codes:

  • P0455 / P0456 (EVAP leak) — appears if the broken pump fails to pressurize the system; usually clears after pump replacement
  • P0496 (EVAP flow during non-purge) — appears if the pump runs when it shouldn't
  • P0446 / P0449 (EVAP vent valve circuit) — separate fault but may share wiring damage
  • P0457 (loose fuel cap) — secondary symptom of failed leak test

  Identify the LDP physical location on your vehicle:

  • VW Atlas, Tiguan, Jetta, Audi Q5/Q7: behind rear passenger-side wheel well liner — access via wheel removal and trim removal
  • Chrysler/Jeep/Dodge: attached to charcoal canister near the fuel tank, usually under the vehicle near the rear axle
  • Toyota/Lexus (older with LDP): bolted onto canister assembly, often above rear wheel or near spare tire well
  • BMW (older models): usually integrated with canister, near fuel tank

  Note: not every vehicle has a separate LDP. Some newer designs integrate leak detection into the fuel tank pressure sensor instead. If you can't locate a discrete pump, check your service manual.

• 2

  Listen for the Cold-Start Rattle — The Free Audible Test

  This is the easiest P2402 diagnostic — costs nothing, confirms the failure in 30 seconds.

  • Park the car for at least 6 hours (overnight is ideal)
  • Open the hood and a rear door just before the leak test runs (about 5 hours after shutoff) — or just listen carefully when you start the car cold
  • Walk to the rear of the vehicle, especially the rear passenger side

  Three possible sounds tell you the diagnosis:

  • Quiet, brief humming (few seconds) = pump is healthy. Cause is elsewhere — go to Step 4.
  • Loud rattling/buzzing for 20-30+ seconds = pump is failing internally. Go to Step 6 (replacement).
  • No sound at all = pump isn't activating. Could be fuse, relay, wiring, or PCM driver. Go to Step 3.

  VW Atlas, Tiguan, and Audi Q5/Q7 owners describe this rattle so consistently in service reports that VW dealerships often confirm P2402 by the sound alone — no scan tool needed. If you can record the sound, share it with any tech and they'll recognize it instantly.
• 3

  Bidirectional Pump Activation — The 30-Second Electrical Test

  If your scanner supports bidirectional EVAP control (UR1000 does), this is the most decisive electrical test:

  • With engine OFF (key on, engine off), navigate to EVAP system bidirectional controls
  • Select "Leak Detection Pump" or "Canister Pump Module" activation
  • Command pump ON for the maximum duration the scanner allows (typically 10-30 seconds)
  • Have a helper listen at the pump location while you command from the cabin

  Three diagnostic outcomes:

  • Pump activates and runs smoothly = pump is electrically OK. Cause is intermittent — likely connector corrosion (Step 5).
  • Pump activates but rattles loudly = pump motor/solenoid failing internally. Replace.
  • Pump doesn't respond at all = electrical path broken. Check fuse, relay, wiring, or driver (Steps 4-5).

  This is the killer step for shops that misdiagnose P2402 as a leak. The pump either responds to direct command or it doesn't — there's no ambiguity. Save yourself a smoke-test session by running this first.
• 4

  Check the EVAP Pump Fuse and Relay

  Before condemning the pump, verify the upstream electrical path:

  • Locate the EVAP fuse — typically in underhood or trunk fuse box. Consult owner's manual; look for labels "EVAP," "LDP," "Canister," or similar
  • Pull fuse and inspect: blown fuse with melted metal = pump shorted internally and took the fuse with it
  • Critical: if the fuse is blown, DO NOT just replace it — the pump that shorted will blow the new fuse immediately. Replace fuse AND pump as a set
  • Test relay (if equipped): swap with identical relay from another circuit. If symptom moves, replace relay (Chrysler/Jeep platforms only — VW/Audi typically have no separate relay)

  A blown EVAP fuse is the #1 sign that the pump shorted internally. It's also the most common reason a "new" pump fails within days of installation — someone replaced the pump but not the fuse, the marginal fuse blew at first activation, and the customer thinks the pump is bad again.
• 5

  Inspect the Pump Connector and Wiring

  Raise the vehicle safely on jack stands and access the LDP location. Unplug the pump connector:

  • Connector pins: green corrosion (very common — pump sits exposed) → clean with electrical contact cleaner; melted plastic = replace pigtail
  • Wire crimps: pull each wire at the back of the connector — if any moves more than 1mm, internal crimp failed
  • Voltage test: KOEO, command pump on via scanner — power wire should pulse to battery voltage. No voltage = upstream wiring or PCM issue
  • Ground continuity: ground wire to chassis should read under 1Ω
  • Wiring harness inspection: trace the harness from pump back as far as you can see — look for chafing, rodent damage, melted insulation

  Apply dielectric grease to the connector pins before reinstalling. This is the #2 most common reason for P2402 returning after repair — the corrosion that triggered the original failure wasn't cleaned during pump replacement.

• 6

  Replace the Leak Detection Pump — The Most Common Fix

  For about 90% of P2402 cases, this is the actual fix. The pump is moderately accessible on most platforms:

  • Order OEM only. Aftermarket pumps for VW Atlas (use OEM 5Q0-906-271-A or revised version), Audi Q5/Q7, and Chrysler/Jeep platforms have very high failure-from-new rates. Buying the cheap one costs you twice
  • Disconnect the negative battery cable before working
  • Raise vehicle safely on jack stands; remove wheel and fender liner on VW/Audi platforms
  • Unplug the pump's electrical connector and EVAP hose (don't break the plastic fitting — flexes back over time but new is brittle)
  • Unbolt the pump mounting bracket (usually 2-3 bolts, 8-10mm or T25 torx)
  • Transfer any mounting hardware from old pump to new pump (rubber isolators, brackets)
  • Install in reverse order — DO NOT cross-thread the EVAP hose fitting (you'll create a real leak that triggers P0455)
  • Reconnect battery, clear codes, and complete a full drive cycle including overnight rest (so the leak test runs)

  After replacement, the EVAP monitor takes 5-10 drive cycles to complete its readiness check. Don't be alarmed if "EVAP not ready" persists for a few days — this is normal. Avoid trying to "force" the monitor with aggressive driving; the test runs on the PCM's schedule, not yours.

How Much Does P2402 Cost to Fix?

P2402 fix costs are relatively predictable because the pump dominates the cause distribution. Most cases land between $130 and $400 DIY.

Per the EPA's emissions standards ↗ EPA Vehicle Emissions I/M Program, a vehicle with an active P2402 code will fail OBD-II emissions inspection — the EVAP monitor cannot complete its readiness check. Some manufacturers offer extended emissions warranty coverage for EVAP components (typically 8 years / 80,000 miles federal). VW has issued service campaigns on Atlas LDP issues — check with your dealer for coverage before paying out of pocket.

Which Vehicles Are Most Prone to P2402?

P2402 only appears on vehicles equipped with a discrete EVAP leak detection pump (LDP). Two platforms generate the bulk of the cases: VW Group (Atlas, Tiguan, Audi Q5/Q7) and Chrysler/Jeep/Dodge (the original LDP design they pioneered). Deep-dives below.

P2402 on VW Atlas, Tiguan, and Audi Q5/Q7 (VW Group MQB Platform)

VW Group's MQB and MLB platforms (2018+ Atlas, Atlas Cross Sport, Tiguan, Jetta, Passat, Audi Q5, Q7) are the highest-volume P2402 generators in North America. The pattern is extremely consistent:

1. The 30-second cold-start rattle (textbook symptom). The LDP is mounted behind the rear passenger-side wheel well liner, exposed to road salt, water spray, and vibration. About 5 hours after engine shutoff, the PCM runs the automated leak test — the pump activates for ~30 seconds. A healthy pump makes a quiet hum. A failing pump rattles loudly enough to be heard from inside the cabin or from outside the rear of the vehicle. This is so consistent that VW dealers often confirm P2402 by the sound alone before scanning.

2. Atlas 2018-2024 service campaign coverage. VW has issued multiple TSBs and service campaigns addressing LDP failure on 2018-2024 Atlas and Atlas Cross Sport. Some are covered under the federal emissions warranty (8 years / 80,000 miles). Always check with your VW dealer with VIN before paying out of pocket — coverage varies by build date and prior service history.

3. The "remote start disabled" giveaway. If your VW Atlas remote start feature stops working at the same time the CEL appears, P2402 is a very strong suspect. VW's connected services intentionally disable remote start when EVAP system faults are active. Once the pump is replaced and codes clear, remote start typically resumes within a day or two.

P2402 on Chrysler / Jeep / Dodge / Ram (Pentastar and HEMI Platforms)

Chrysler pioneered the LDP design in the late 1990s, and modern Stellantis platforms still use a variant called the Canister Pump Module (CPM). Common pattern across Grand Cherokee, Wrangler, Cherokee, 300, Charger, Challenger, Pacifica, and Ram 1500:

1. The Canister Pump Module failure at 80,000-120,000 miles. The CPM is mounted near the charcoal canister, typically attached to the fuel tank area on the underside of the vehicle. It's exposed to road salt and water more aggressively than VW's wheel-well-mounted design. Failure modes are nearly identical to VW: stuck-on solenoid, worn motor, internal short. Replacement CPM (Mopar OE) is $120-$250 — less expensive than VW's pump.

2. Common companion code: P0496. Chrysler platforms frequently set P2402 alongside P0496 (EVAP flow during non-purge condition). The relationship is direct: a stuck-on CPM keeps the EVAP system pressurized when it shouldn't be, triggering the flow code. Fix the CPM (P2402), and P0496 typically clears on the next drive cycle.

3. The fuse-blow signature. Chrysler CPMs tend to fail by drawing excess current rather than rattling like VW pumps. The result: the EVAP fuse (typically in the underhood fuse box) blows. Replacing only the fuse without replacing the CPM means the new fuse blows immediately. Always inspect the fuse on Chrysler P2402 cases AND plan to replace both the fuse and the CPM as a set.

Should You DIY or Call a Mechanic?

Related Codes You May See With P2402

Frequently Asked Questions