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DTC P1494: Leak Detection Pump Pressure Switch

NOTE: For connector terminal ID, see CONNECTOR IDENTIFICATION  . For wiring diagram, see WIRING DIAGRAMS article.
NOTE: Leak detection pump may also be referred to as EVAP leak detection pump. Leak detection pump pressure switch operation is monitored immediately after a cold start with ambient temperature of 40-90°F (4.4-32.0°C) and engine coolant temperature is within 10°F (-12°C) of ambient temperature. DTC may be stored in Powertrain Control Module (PCM) if state of leak detection pump pressure switch does not change when leak detection pump solenoid is energized. Possible causes are: leaking or restricted hose, defective leak detection pump, defective PCM, or defective connectors or wiring.
  1. Start engine and allow engine to idle. Go to LEAK DETECTION PUMP TEST on scan tool and observe Leak Detection Pump (LDP) pressure switch state. While still in LEAK DETECTION PUMP TEST, press "1" on scan tool keypad and then press down arrow on scan tool several times while monitoring LDP pressure switch state. LDP pressure switch state may also be referred to as LEAK DETECT PUMP SW state. LDP pressure switch state should change from OPEN (UP) to CLOSED (DN). If LDP pressure switch state changes as specified, go to next step. If LDP pressure switch state does not change as specified, go to step  5 .
  2. Shut engine off. Turn ignition on with engine off. Using scan tool, read DTCs and record FREEZE FRAME data. Using scan tool, clear DTCs from PCM. Start engine and allow engine to idle. Using scan tool, perform LDP monitor test while wiggling wiring harness and connectors from leak detection pump to PCM. Leak detection pump is located below driver's side of steering gear, above engine cradle. See Fig 1 . PCM is located between driver's side front fender and power distribution center, near battery.
    Fig 1: Locating Leak Detection Pump & Identifying Hoses
    G95C35065Courtesy of DAIMLERCHRYSLER CORPORATION
  3. Stop LDP monitor test. Using scan tool, check for DTCs. If DTC P1494: LEAK DETECTION PUMP PRESSURE SWITCH does not exist, go to next step. If DTC P1494: LEAK DETECTION PUMP PRESSURE SWITCH exists, repair wiring or connectors between leak detection pump and PCM as necessary that caused DTC to be set. Perform TEST VER-5A  .
  4. Ensure ignition is off. Inspect wiring harness and connectors between leak detection pump and PCM. If no problems exist, test is complete. If any problems exist, repair wiring or connectors as necessary. Perform TEST VER-5A  .
  5. Turn ignition off. Disconnect leak detection pump connector. Leak detection pump is located below driver's side of steering gear, above engine cradle. See Fig 1 .
  6. Turn ignition on with engine off. Using voltmeter, check voltage at terminal No. 2 (White/Black wire) on leak detection pump connector. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, repair open on White/Black wire to leak detection pump. White/Black wire is the fused ignition switch output which supplies voltage to leak detection pump from ignition switch, through Positive Temperature Coefficient (PTC) No. 1, to power distribution center, and then to leak detection pump. PTC No. 1 is a specified amperage solid-state circuit breaker which receives voltage when ignition is on and may be reset when all current is removed from PTC for approximately 20 seconds. PTC No. 1 is located in junction block behind driver's side of instrument panel, to left of steering column. Perform TEST VER-5A  .
  7. Turn ignition off. Disconnect engine vacuum hose at leak detection pump. See Fig 1 . This is the engine vacuum supply hose from engine to leak detection pump. Install vacuum gauge on engine vacuum hose at leak detection pump and at engine vacuum source. Start engine and note vacuum readings. Vacuum at engine vacuum hose at leak detection pump should be within one in. Hg of the engine vacuum.
  8. If vacuum at engine vacuum hose at leak detection pump is within one in. Hg of engine vacuum, remove vacuum gauges, reinstall engine vacuum hose and go to next step. If vacuum at engine vacuum hose at leak detection pump is not within one in. Hg of engine vacuum, remove vacuum gauges and repair leak or obstruction on engine vacuum hose to leak detection pump. Perform TEST VER-5A  .
  9. Ensure ignition is off. Disconnect PCM connectors. PCM is located between driver's side front fender and power distribution center, near battery.
  10. Ensure leak detection pump connector is still disconnected. Using ohmmeter, check resistance between ground and terminal No. 72 (Yellow/Black wire on 2.4L or Dark Blue/White wire on 3.3L and 3.8L) on Gray PCM connector C2. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground on Yellow/Black on 2.4L or Dark Blue/White wire on 3.3L and 3.8L between PCM and leak detection pump. Perform TEST VER-5A  .
  11. Using ohmmeter, check resistance between terminal No. 4 (Yellow/Black wire on 2.4L or Dark Blue/White wire on 3.3L and 3.8L) on leak detection pump connector and terminal No. 72 (Yellow/Black wire on 2.4L or Dark Blue/White wire on 3.3L and 3.8L) on Gray PCM connector C2. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open on Yellow/Black wire on 2.4L or Dark Blue/White wire on 3.3L and 3.8L between PCM and leak detection pump. Perform TEST VER-5A  .
  12. Disconnect engine vacuum hose at leak detection pump. See Fig 1 . This is the engine vacuum supply hose from engine to leak detection pump. Connect vacuum pump to engine vacuum hose port on leak detection pump. Reinstall leak detection pump connector.
  13. Turn ignition on with engine off. Connect voltmeter between ground and terminal No. 72 (Yellow/Black wire on 2.4L or Dark Blue/White wire on 3.3L and 3.8L) on Gray PCM connector C2. Connect jumper wire between ground and terminal No. 77 (White/Dark Green wire) on Gray PCM connector C2 and note voltage reading. This will energize leak detection pump solenoid.
  14. Using vacuum pump, apply vacuum to leak detection pump while noting voltage reading. If voltage changes when applying vacuum on leak detection pump, replace PCM. Perform TEST VER-5A  . If voltage does not change when applying vacuum on leak detection pump, replace leak detection pump. Perform TEST VER-5A  .
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