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Malfunction Indicator Light Circuit Diagnosis

CAUTION: Manufacturer recommends using backprobe wire set (07SAZ-001000A) for testing connectors and terminals.
  1. Turn ignition on and watch MIL. If MIL never comes on, go to next step. If MIL comes on and stays on for more than 2 seconds or comes on after 2 seconds, go to step  5 . If MIL operates intermittently, check for a loose No. 14 (15-amp) fuse in underdash fuse relay/box, poor connection at PCM connector "A" (32-pin connector) terminal No. 18, and/or an intermittent open in Gray/Red wire between instrument panel and PCM connectors. See Figure and WIRING DIAGRAMS article.
  2. Turn ignition off, and then on again. If charge system light is on, go to next step. If charge system light is not on, replace No. 14 (15-amp) fuse and repair short or open in Black/Yellow wire between No. 14 (15-amp) fuse and instrument panel. See WIRING DIAGRAMS article.
  3. Try to start engine. If engine does not start, go to next step. If engine starts, turn ignition off. Using a jumper wire, connect PCM connector "A" (32-pin connector) terminal No. 18 (Gray/Red wire) to body ground. See Figure . Turn ignition on. If MIL is on, substitute known-good PCM and retest. See SUBSTITUTING POWERTRAIN CONTROL MODULE  . If symptom/indication goes away, replace original PCM. If MIL is not on, check for open in Gray/Red wire between PCM connector "A" (32-pin connector) terminal No. 18 and instrument panel. Also check for blown MIL bulb. If wire and MIL bulb are okay, replace instrument panel assembly. Perform final procedure. See FINAL PROCEDURE  .
  4. Turn ignition on. Backprobing, measure voltage between ground and PCM connector "A" (32-pin connector) terminals No. 10 and 23 (Black wires), individually. See Figure . If voltage reading is less than one volt, substitute known-good PCM and retest. See SUBSTITUTING POWERTRAIN CONTROL MODULE  . If symptom/indication goes away, replace original PCM. If voltage reading is not less than one volt, repair open in suspect Black wire between PCM and ground point located at right side of engine, below VTEC pressure switch. See WIRING DIAGRAMS article.
  5. If MIL comes on and stays on for more than 2 seconds or comes on after 2 seconds, go to next step. If this symptom is intermittent, check the following:
    • Loose No. 4 (10-amp) fuse located in underdash fuse/relay box.
    • Loose No. 23 (15-amp) fuse located in Supplemental Restraint System (SRS) fuse block, located above underdash fuse/relay box.
    • Intermittent short in Red/White wire between PCM connector "C" (31-pin connector) terminal No. 7 and 2-pin service check connector located at right side of center console behind access cover. See Figure and Figure .
    • Intermittent short in Gray/Red wire between PCM connector "A" (32-pin connector) terminal No. 18 and instrument panel. See Figure and WIRING DIAGRAMS article.
    • Intermittent short in Yellow/Red wire between PCM connector "D" (16-pin connector) terminal No. 4 and MAP sensor. See Figure and WIRING DIAGRAMS article.
    • Intermittent short in Yellow/Blue wire between PCM connector "D" (16-pin connector) terminal No. 10 and TP sensor, EGR valve lift sensor and/or Fuel Tank Pressure (FTP) sensor. See WIRING DIAGRAMS article.
    • Faulty PGM-FI main relay.

    Perform repairs as necessary and recheck MIL operation. If no problems are found, go to next step.

  6. Turn ignition off. Connect scan tool to 16-pin Data Link Connector (DLC) located at right side of center console behind access cover. See Figure . Turn ignition on and read DTCs. See RETRIEVING DIAGNOSTIC TROUBLE CODES  . If no DTCs are present, go to next step. If DTCs are present, go to DIAGNOSTIC TROUBLE CODE IDENTIFICATION  and perform designated diagnostics.
    7. NOTE: If SCS Service Connector is connected when ignition switch is turned on and no Diagnostic Trouble Codes (DTC) are stored in the Powertrain Control Module (PCM), Malfunction Indicator Light (MIL) will stay on.
  7. Turn ignition off. Connect SCS Service Connector to 2-pin service check connector. See Figure . Turn ignition on. If MIL does not indicate any DTCs are present, go to next step. If MIL indicates DTCs are present, repair open or short in Light Green wire between PCM connector "C" (31-pin connector) terminal No. 8 and DLC terminal No. 15. See Figure and Figure . After repair, perform final procedure and retest. Perform final procedure. See FINAL PROCEDURE  . If DTCs are present, go to DIAGNOSTIC TROUBLE CODE IDENTIFICATION  and perform designated diagnostics.
  8. Attempt to start engine. If engine starts, go to next step. If engine does not start, go to step  11 .
  9. Stop engine. Turn ignition on. Backprobing, measure voltage between PCM connector "C" (31-pin connector) terminal No. 7 (Red/White wire) and PCM connector "D" (16-pin connector) terminal No. 11 (Green/Black wire). See Figure and Figure . If voltage reading is about 5 volts, go to next step. If voltage reading is not about 5 volts, repair short to ground in appropriate wire (Red/White or Green/Black) between 2-pin service check and PCM connectors. See WIRING DIAGRAMS article.
  10. Turn ignition off. Disconnect PCM connector "A" (32-pin connector). Turn ignition on. If MIL is on, repair short to ground in Gray/Red wire between instrument panel and PCM connectors. If MIL is not on, substitute known-good PCM and retest. See SUBSTITUTING POWERTRAIN CONTROL MODULE  . If symptom/indication goes away, replace original PCM. Perform final procedure. See FINAL PROCEDURE  .
  11. Inspect No. 4 (10-amp) fuse in underdash fuse/relay box. If fuse is okay, go to next step. If fuse is not okay, replace fuse and repair short in White/Green wire between underdash fuse/relay box and PGM-FI main relay.
  12. Inspect No. 23 (15-amp) fuse located in Supplemental Restraint System (SRS) fuse block, located above underdash fuse/relay box. If fuse is okay, go to next step. If fuse is not okay, replace fuse and repair short in Red/Orange wire between SRS fuse block and PGM-FI main relay.
  13. Turn ignition on. Disconnect each of the following sensors, one at a time, and watch MIL.
    • MAP sensor 3-pin connector
    • TP sensor 3-pin connector
    • EGR valve lift sensor 3-pin connector
    • FTP sensor 3-pin connector

      If MIL does not go out when each sensor is disconnected, go to next step. If MIL goes out when a sensor is disconnected, replace sensor that caused MIL to go out.

  14. Turn ignition off. Disconnect PCM connector "D" (16-pin connector). Check continuity between body ground and PCM connector "D" (16-pin connector) terminals No. 4 (Yellow/Red wire) and No. 10 (Yellow/Blue wire), individually. See Figure . If continuity is not present at either test point, go to next step. If continuity is present at both test points, repair short to ground in Yellow/Red wire between MAP sensor and PCM connectors and/or repair short to ground in Yellow/Blue wire between TP sensor, EGR valve lift sensor and/or FTP sensor and PCM connectors. See WIRING DIAGRAMS article.
  15. Disconnect IAC valve and fuel injector connectors. Turn ignition on. Backprobing, check voltage between body ground and PCM connector "A" (32-pin connector) terminals No. 11 and 24 (Yellow/Black wires), individually. See Figure . If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Yellow/Black wires between PCM and PGM-FI main relay connectors and/or check for poor connections or loose wires at PGM-FI main relay. If connections and wires are okay, check PGM-FI main relay. See RELAYS under RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article.
  16. Turn ignition off. Reconnect all sensor connectors and PCM connector "D" (16-pin connector). Turn ignition on. Backprobing, measure voltage between ground and PCM connector "A" (32-pin connector) terminals No. 9 and 22 (Brown/Black wires), individually. See Figure . If voltage is less than one volt, substitute known-good PCM and retest. See SUBSTITUTING POWERTRAIN CONTROL MODULE  . If symptom or indication goes away, replace original PCM. If voltage for either terminal is not less than one volt, repair open in appropriate Brown/Black wire between PCM connector and ground point located at right side of engine, below VTEC pressure switch. Perform final procedure. See FINAL PROCEDURE  .
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