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HOMESERVICE MANUALSACURA20043.5RLREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - BASIC DIAGNOSTIC PROCEDURESFUEL SYSTEMPGM-FI MAIN RELAY CIRCUIT TESTINGMDX
2004 Acura 3.5RL

PGM-FI Main Relay Circuit Testing: MDX

2004 Acura 3.5RLSECTION MDX
  1. Listen for fuel flow noise at fuel injector rail under intake manifold cover. Fuel pump should operate for 2 seconds after ignition switch is turned on. If fuel pump operates as specified, fuel pump is okay. If fuel pump does not operate as specified, go to next step.
  2. Turn ignition on. With the Honda PGM Tester or the HDS, do the DTC CLEAR in the CLEAR menu. Start the engine. Check for Temporary DTCs or DTCs. If DTC P0657 is set, troubleshoot first. See DTC P0657: AIR FUEL RATIO SENSOR RELAY CIRCUIT MALFUNCTION under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - MDX article. If DTC P0657 is not indicated, go to next step.
  3. Remove lower dashboard cover and disconnect PGM-FI main relay No. 2, located in the middle of dash. Turn ignition on. Using a voltmeter measure voltage between ground and 5-pin relay connector terminal No. 1. If battery voltage is not present, check for faulty No. 1 FUEL PUMP (15-amp) fuse in driver's underdash fuse/relay box. Repair as necessary. If battery voltage is present, go to next step.
  4. Turn ignition switch off. Remove second row seat. Cut carpet on dotted line. See Fig 1 . Be careful not to cut wire harness under carpet. Remove fuel pump access panel. Go to next step. Within the first 2 seconds after turning ignition on, measure voltage between ground and fuel pump harness connector terminal No. 5 (Red/Orange wire). If battery voltage is present, go to step  7 . If battery voltage is not present, go to next step.
  5. Turn ignition off. Disconnect PGM-FI main relay No. 2. Connect a fused jumper wire between PGM-FI main relay harness connector terminals No. 1 and 2. See Fig 2 . Go to next step.
  6. Turn ignition on. Measure voltage between ground and fuel pump harness connector terminal No. 5 (Red/Orange wire). If battery voltage is not present, check for faulty circuit between fuel pump, PGM-FI main relay No.2 and fuel pump harness connector. See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. Repair as necessary. If battery voltage is present, replace PGM-FI main relay No. 2 (FUEL PUMP).
  7. Turn ignition off. Check for continuity between ground and fuel pump connector terminal No. 4 (Brown/Black wire). If there is no continuity, repair wire between fuel pump harness connector and ground connector G601. If there is continuity, replace fuel pump.
Fig 1: Identifying Fuel Pump Access Location (MDX)
G00070905Courtesy of AMERICAN HONDA MOTOR CO., INC.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.