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DTC Test No. 87: LDP Switch/Mechanical Fault

NOTE: Before performing this test procedure, repair all other non-EVAP related DTCs. If more than one EVAP related code exists, repair in the following order: DTC 183 (DTC TEST NO. 86 ), DTC 184 (DTC TEST NO. 87 ), DTC 187 (DTC TEST NO. 89 ) then DTC 160/161 (DTC TEST NO. 82 ).
NOTE: Leak detection pump switch is an integral part of leak detection pump. Immediately after a cold start, if all leak detection test enabling conditions are met, the PCM detects the status of leak detection pump switch. DTC is set if status of leak detection pump switch does not change when leak detection pump solenoid is energized. Possible causes for DTC to set are: insufficient vacuum to leak detection pump, defective leak detection pump, defective leak detection pump switch, defective PCM, or defective connectors or wiring.
  1. Remove and reinstall fuel tank cap. This will eliminate the possibility of residual pressure in fuel tank or EVAP system that may cause a misleading reading. Turn ignition on. Using scan tool, enter leak detection pump hold mode. Observe leak detection pump switch, solenoid and vent valve status. Check leak detection pump switch status on scan tool. If scan tool displays OFF:UP, go to next step. If scan tool displays ON:DN, go to step  10.
    2. NOTE: In the following steps do not use a DVOM, analog meter or LED test light.
  2. Turn ignition off. Disconnect leak detection pump harness connector. Leak detection pump is located on a mounting bracket on front of fuel tank. See Figure. Turn ignition on. Connect a test light between terminals No. 2 (Black/White wire) and No. 4 (Red/Blue wire) at leak detection pump harness connector. See Figure. If test light illuminates, leave test light connected and go to next step. If test light does not illuminate, leave test light connected and go to step  5.
  3. Turn ignition off. Disconnect Powertrain Control Module (PCM) harness connectors. PCM is located at left front corner of engine compartment, in front of Electronic Automatic Transmission Electronic Control Module (EATX-ECM), near relay box. Turn ignition on. If test light is still illuminated, go to next step. If test light is not still illuminated, replace PCM and confirm test light does not come on. Also replace leak detection pump, since it may have been damaged by the high current from short to ground condition. Perform readiness test. See TEST NTC-49: READINESS TEST .
  4. Turn ignition off. A short to ground exists in circuit between leak detection pump and PCM. Check for a short to ground in Red/Blue wire between leak detection pump and PCM. Inspect leak detection pump connector for damaged wires or terminals. Inspect in-line harness connector E-08 for damaged wires or terminals. In-line harness connector E-08 is located under rear seat. See Figure. Inspect junction box harness connector B-41 for damaged wires or terminals. Junction box is located behind left side of instrument panel. See Figure. Inspect PCM connectors for damaged wires or terminals. Repair or replace wiring and/or connector(s) as necessary. After repairing short to ground, replace leak detection pump, since it may have been damaged by the high current from short to ground condition. Perform readiness test. See TEST NTC-49: READINESS TEST .
  5. Check leak detection pump switch status on scan tool. If scan tool displays ON:DN, go to next step. If scan tool displays OFF:UP, go to step  7.
  6. Turn ignition off. Inspect leak detection pump connector for damage. If problem exists, repair connector as necessary. Perform readiness test. See TEST NTC-49: READINESS TEST . If problem does not exist, replace leak detection pump. Perform readiness test. See TEST NTC-49: READINESS TEST .
  7. Turn ignition off. Disconnect Powertrain Control Module (PCM) harness connectors. PCM is located at left front corner of engine compartment, in front of Electronic Automatic Transmission Electronic Control Module (EATX-ECM), near relay box. Measure resistance in Red/Blue wire between terminal No. 4 (Red/Blue wire) at leak detection pump harness connector and terminal No. 72 (Red/Blue wire) at PCM harness connector A-78. See Figure and Figure . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, go to step  9.
  8. Inspect leak detection pump connector and PCM connectors for damage. If problem exists, repair as necessary. Perform readiness test. See TEST NTC-49: READINESS TEST . If problem does not exist, replace PCM. Perform readiness test. See TEST NTC-49: READINESS TEST .
  9. An open exists between leak detection pump and PCM. Check for an open in Red/Blue wire between leak detection pump and PCM. Inspect leak detection pump connector for damaged wires or terminals. Inspect in-line harness connector E-08 for damaged wires or terminals. In-line harness connector E-08 is located under rear seat. See Figure. Inspect junction box harness connector B-41 for damaged wires or terminals. Junction box is located behind left side of instrument panel. See Figure. Inspect PCM connectors for damaged wires or terminals. Repair or replace wiring and/or connector(s) as necessary. After repairing open, perform readiness test. See TEST NTC-49: READINESS TEST .
  10. Start engine and let idle. Using scan tool in hold mode, activate leak detection pump solenoid. Leak detection pump solenoid state should change from VACBLC (vacuum blocked) to VACAPP (vacuum applied). Also leak detection pump switch state should change from ON:DN to OFF:UP as diaphragm moves up. If leak detection pump states do not change as specified, go to next step. If leak detection pump states change as specified, failure is intermittent. See INTERMITTENT MALFUNCTION .
  11. If PCM does not detect leak detection pump switch status change, scan tool will display NOW HOLDING, PLEASE APPLY THE VACUUM. With engine idling, disconnect vacuum supply hose at leak detection pump and connect a vacuum gauge to disconnected vacuum supply hose. Observe idle when disconnecting hose. If no noticeable idle flare occurs immediately after disconnecting hose, vacuum reading is not strong, steady, and within one in. Hg of intake manifold vacuum, go to next step. If a noticeable idle flare occurs immediately after disconnecting hose, vacuum reading is strong, steady, and within one in. Hg of intake manifold vacuum, go to step  14.
  12. Disconnect purge hose at leak detection pump. Use a hand-held vacuum pump, apply vacuum to vacuum nipple and verify vacuum is maintained. Check for blockage or leaks in vacuum supply hose between intake plenum and leak detection pump. Repair vacuum supply problem as necessary. Check for blockage at intake plenum nipple. Go to next step.
  13. After correcting vacuum supply malfunction, confirm that leak detection pump is operating properly. Start engine and let idle. Using scan tool in HOLD MODE, press YES to activate leak detection pump solenoid. Scan tool should display VACBLC (vacuum blocked) to VACAPP (vacuum applied). Also leak detection pump switch state should change from ON:DN to OFF:UP as diaphragm moves up. If leak detection pump switch state does not change as described, failure was not repaired. Go to step  1. If leak detection pump switch state changes as described, perform readiness test. See TEST NTC-49: READINESS TEST .
  14. Disconnect leak detection pump harness connector. Using scan tool, check leak detection pump switch state. Leak detection pump switch state should change from ON:DN to OFF:UP as diaphragm moves up. If leak detection pump switch state changes as specified, replace leak detection pump. Perform readiness test. See TEST NTC-49: READINESS TEST . If leak detection pump switch state does not change as specified (remains ON:DN), go to next step.
  15. Check for a short to voltage in Red/Blue wire between leak detection pump and PCM. Inspect leak detection pump connector for damaged wires or terminals. Inspect in-line harness connector E-08 for damaged wires or terminals. In-line harness connector E-08 is located under rear seat. See Figure. Inspect junction box harness connector B-41 for damaged wires or terminals. Junction box is located behind left side of instrument panel. See Figure. Inspect PCM connectors for damaged wires or terminals. If problem exists, repair or replace wiring and/or connector(s) as necessary. Perform readiness test. See TEST NTC-49: READINESS TEST . If problem does not exist, replace PCM. Perform readiness test. See TEST NTC-49: READINESS TEST .
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