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DTC codes / BMW codes / P1442

P1442 · BMWLeakage Diagnostic Pump Control Circuit Signal Low

P1442 on BMW vehicles means the engine control module (DME) has detected a low signal on the control circuit for the leakage diagnostic pump, which is the electric pump used for evaporative emissions testing. The DME commands the pump on and monitors the circuit voltage; a low signal indicates the circuit is shorted to ground, the pump winding is open or shorted, or the DME driver is faulty.

SystemPowertrain
Code typeBMW specific
SeverityLow
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • A slight fuel odor around the rear of the vehicle if the pump or its seal is compromised
  • Failed emissions inspection due to an incomplete evaporative system monitor
  • In rare cases, a rough idle or stumble after refueling if the pump circuit interferes with purge flow
  • Intermittent warning light that appears after the vehicle sits overnight and the DME runs its leak test

Common causes, most likely first

  1. Broken, chafed, or corroded wiring between the DME and the leakage diagnostic pump, especially at the connector or where the harness passes near the rear axle
  2. Failed leakage diagnostic pump (open or shorted internal winding) causing the control circuit to read low
  3. Corroded or loose electrical connector at the pump or at the DME, introducing resistance or a short to ground
  4. Faulty DME driver stage for the pump control circuit, often after water intrusion or a previous short
  5. Blown fuse or relay supplying power to the leakage diagnostic pump, though this usually sets a different code
  6. Aftermarket alarm or audio installation tapping into the rear harness and creating a short to ground

How to diagnose and fix it

  1. Clear the code and perform a road test with a scan tool to confirm P1442 returns and to check for related evaporative system codes.
  2. Visually inspect the leakage diagnostic pump, its connector, and the harness routing for damage, corrosion, or signs of rodent chewing.
  3. Disconnect the pump and measure resistance across its control terminals; compare to BMW specifications to rule out an open or shorted pump.
  4. With the pump disconnected, check for continuity to ground on the control wire from the DME; a short to ground confirms a harness fault.
  5. Backprobe the control circuit at the DME while commanding the pump on with a scan tool; a low signal with a known-good pump points to a faulty DME.
  6. Repair or replace the faulty harness section, connector, or pump as indicated by the tests, then clear codes and verify the evaporative monitor completes.
  7. If the DME driver is confirmed faulty, have the unit rebuilt or replaced and coded by a qualified BMW specialist.

What BMW leak pump diagnostics miss

  • A low signal on the control circuit is often caused by water intrusion into the pump connector, not by a failed pump, so always inspect the connector pins for green corrosion before condemning the pump.
  • The DME runs the leak test only under specific conditions such as a cold engine and a fuel level between certain limits, so a P1442 may not reappear immediately after clearing and can fool a quick test drive.
  • A shorted purge valve or charcoal canister can back-feed the pump circuit and set P1442, so technicians who replace only the pump often see the code return.
  • Aftermarket remote starters or alarm systems that tap into the rear wiring harness are a frequent hidden cause of a low signal on this circuit on older BMW models.
  • P1442 does not always mean the pump has failed; a chafed wire against the rear subframe can intermittently short to ground only when the suspension moves, making the fault hard to reproduce in the shop.

Can I keep driving with P1442?

The vehicle remains safe to drive because the leakage diagnostic pump only affects evaporative emissions testing and does not influence engine performance or safety systems. Avoid topping off the fuel tank past the first click and schedule diagnosis soon, since a persistent fault will prevent the emissions monitor from completing and may mask a real fuel vapor leak.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for BMW vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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