Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DLC Circuit Troubleshooting
- Turn the ignition switch to LOCK (0).
- Connect the HDS to the DLC (see HOW TO USE THE HDS (HONDA DIAGNOSTIC SYSTEM) ).
- Turn the ignition switch to ON (II), and read the HDS.
Does the HDS identify the vehicle?
YES -Go to step 4.
NO -Go to step 21.
- Check for Pending or Confirmed DTCs in the PGM-FI system with the HDS.
Are any Pending or Confirmed DTCs indicated?
YES -Go to the indicated DTC's troubleshooting.
NO -
- If the HDS does not communicate with the SRS, go to step 5.
- If the HDS does not communicate with the VSA system, go to step 7.
- If the HDS does not communicate with the TPMS, go to step 9.
- If the HDS does not communicate with the IMMOBI (immobilizer) system, go to step 11.
- If the HDS does not communicate with the BODY ELECTRICAL system, go to step 13.
- Turn the ignition switch to LOCK (0).
- Turn the ignition switch to ON (II), and watch the SRS indicator.
Does the SRS indicator come on and go off?
YES -Go to step 15.
NO -Go to the SRS symptom troubleshooting for SRS indicator stays on, but no DTCs are set (see SRS INDICATOR STAYS ON, BUT NO DTCS ARE STORED, OR CANNOT BE READ ).
- Turn the ignition switch to LOCK (0).
- Turn the ignition switch to ON (II), and watch the VSA indicator.
Does the VSA indicator come on and go off?
YES -Go to step 15.
NO -Go to the VSA system symptom troubleshooting for an ABS indicator, brake system indicator, and VSA indicator do not go off (see SYMPTOM TROUBLESHOOTING ).
- Turn the ignition switch to LOCK (0).
- Turn the ignition switch to ON (II), and watch the TPMS indicator.
Does the TPMS indicator come on and go off?
YES -Go to step 15.
NO -Go to the TPMS symptom troubleshooting for TPMS indicator does not go off, and no DTCs are stored (see TPMS INDICATOR DOES NOT GO OFF, AND NO DTCS ARE STORED ).
- Turn the ignition switch to LOCK (0).
- Turn the ignition switch to ON (II), and watch the immobilizer indicator.
Does the immobilizer indicator stay on or flash?
YES -Go to the immobilizer symptom troubleshooting (see SYMPTOM TROUBLESHOOTING INFORMATION ).
NO -Go to step 15.
- Do the gauge self-diagnostic function (see SELF-DIAGNOSTIC FUNCTION ).
- Check the gauge display.
Is Error 2 indicated?
YES -Check for B-CAN system DTCs (see GENERAL TROUBLESHOOTING INFORMATION ).
NO -Go to step 15.
- Turn the ignition switch to LOCK (0), then do the battery terminal disconnection procedure (see DISCONNECTION ), and wait at least 3 minutes before continuing.
- Disconnect the HDS from the DLC.
- Check for continuity between DLC terminal No. 7 and body ground.
Is there continuity?
YES -Go to step 18.
NO -Go to step 19.
- Continue to check for continuity between DLC terminal No. 7 and body ground while disconnecting these connectors, one at a time:
- SRS unit connector A (28P)
- VSA modulator-control unit 46P connector
- TPMS control unit 20P connector
- Immobilizer-keyless control unit 7P connector
- Audio unit connector A (24P)
- Under-dash fuse/relay box connector Q (16P)
Does continuity go away when one of the above connectors is disconnected?
YES -Replace the part that caused an open when it was disconnected.
NO -Repair a short in the wire between the DLC (K-line) and the VSA modulator-control unit, the SRS unit, the TPMS control unit, the immobilizer-keyless control unit, the audio unit, or the under-dash fuse/relay box.
- Connect DLC terminal No. 7 to body ground with a jumper wire.
- Check for continuity between body ground and these connector terminals:CONNECTOR TERMINAL CHART
Connector Terminal SRS unit A (28P) No. 24 (LT BLU) VSA modulator-control unit 46P No. 15 (LT BLU) TPMS control unit 20P No. 7 (LT BLU) Immobilizer-keyless control unit 7P No. 5 (LT BLU) Audio unit A (24P) No. 3 (LT BLU) Under-dash fuse/relay box Q(16P) No. 8 (LT BLU) Is there continuity between body ground and each of the terminals in the chart?
YES -Replace the part that does not communicate with the HDS.
NO -Repair an open in the wire between the DLC (K-line) and the appropriate connector.
- Check for B-CAN system DTCs without the HDS (see
GENERAL TROUBLESHOOTING INFORMATION
).
Is DTC U0029 and/or U0100 indicated?
YES -Go to step 32.
NO -Go to step 22.
- Turn the ignition switch to LOCK (0).
- Disconnect the HDS from the DLC.
- Measure the voltage between DLC terminal No. 16 and body ground.
Is there battery voltage?
YES -Go to step 25.
NO -Repair an open in the wire between DLC terminal No. 16 and the No. 23 BACK UP (10 A) fuse in the under-hood fuse/relay box.
- Measure the voltage between DLC terminals No. 4 and No. 16.
Is there battery voltage?
YES -Go to step 26.
NO -Repair an open in the wire between DLC terminal No. 4 and body ground (G502) (see STARTER SUBHARNESS ('07-09 MODELS) ).
- Connect the HDS to the DLC.
- Jump the SCS line with the HDS.
- Disconnect PCM connector A (49P).
- Disconnect the HDS from the DLC.
- Check for continuity between PCM connector terminal A3 and DLC terminal No. 6.
Is there continuity?
YES -Go to step 31.
NO -Repair an open in the wire between the PCM (A3) and DLC terminal No. 6.
- Check for continuity between PCM connector terminal A4. and DLC terminal No. 14.
Is there continuity?
YES -Update the PCM if it does not have the latest software (see PCM Update ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ).
NO -Repair an open in the wire between the PCM (A4) and DLC terminal No. 14.
- Try to start the engine.
Does the engine start and idle smoothly?
YES -Go to the F-CAN circuit troubleshooting (see F-CAN CIRCUIT TROUBLESHOOTING ).
NO -Go to step 33.
- Turn the ignition switch to LOCK (0).
- Check the No. 2 IG MAIN (50 A) fuse in the under-hood fuse/relay box.
Is the fuse OK?
YES -Repair an open in the wire between the No. 2 IG MAIN (50 A) fuse and the ignition switch. If the wire is OK, go to step 35.
NO -Repair a short in the wire between the No. 2 IG MAIN (50 A) fuse and the ignition switch. Also replace the No. 2 IG MAIN (50 A) fuse.
- Inspect the No. 19 Fl MAIN (15 A) fuse in the under-hood fuse/relay box.
Is the fuse OK?
YES -Go to step 42.
NO -Go to step 36.
- Remove the blown No. 19 FI MAIN (15 A) fuse from the under-hood fuse/relay box.
- Remove PGM-FI main relay 1 (A) from the under-hood fuse/relay box.
- Check for continuity between body ground and PGM-FI main relay 1 4P connector terminals No. 1 and No. 3 individually.Fig 8: Checking Continuity Between Body Ground And PGM-FI Main Relay 1 4P Connector Terminals No. 1 And No. 3
Is there continuity?
YES -Replace the under-hood fuse/relay box (see REMOVAL AND INSTALLATION ). Also replace the No. 19 Fl MAIN (15 A) fuse.
NO -Go to step 39.
- While disconnecting each of the parts or connectors below, one at a time, check for continuity between PGM-FI main relay 1 4P connector terminal No. 2 and body ground:
- PGM-FI main relay 2 (FUEL PUMP)
- PCM connector A (49P)
- Each injector 2P connector
- Camshaft position (CMP) sensor B 3P connector
- Crankshaft position (CKP) sensor 3P connector
- MAF sensor/IAT sensor 5P connector
- Electronic throttle control system (ETCS) control relay
Does continuity go away when one of the above parts or connectors is disconnected?
YES -Replace the part that made the short to body ground go away when disconnected. If the part is the PCM, update the PCM if it does not have the latest software (see PCM Update ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ). Also replace the No. 19 Fl MAIN (15 A) fuse.
NO -Go to step 40.
- Disconnect the connectors from these parts:
- PGM-FI main relay 2 (FUEL PUMP)
- PCM connector A (49P)
- Injectors
- Camshaft position (CMP) sensor B
- MAF sensor/IAT sensor
- Crankshaft position (CKP) sensor
- Electronic throttle control system (ETCS) control relay
- Check for continuity between PGM-FI main relay 1 4P connector terminal No. 2 and body ground.
Is there continuity?
YES -Repair a short in the wire between PGM-FI main relay 1 and each part. Also replace the No. 19 Fl MAIN (15 A) fuse.
NO -Replace PGM-FI main relay 1. Also replace the No. 19 Fl MAIN (15 A) fuse.
- Inspect the No. 2 FUEL PUMP (15 A) fuse in the under-dash fuse/relay box.
Is the fuse OK?
YES -Go to step 54.
NO -Go to step 43.
- Remove the blown No. 2 FUEL PUMP (15 A) fuse from the under-dash fuse/relay box.
- Remove PGM-FI main relay 2 (FUEL PUMP) (A) from the under-dash fuse/relay box.
- Test PGM-FI main relay 2 (FUEL PUMP) (see
POWER RELAY TEST
).
Is the relay OK?
YES -Go to step 46.
NO -Replace PGM-FI main relay 2 (FUEL PUMP). Also replace the No. 2 FUEL PUMP (15 A) fuse.
- Check for continuity between PGM-FI main relay 2 (FUEL PUMP) 4P connector terminal No. 2 and body ground.Fig 12: Checking Continuity Between PGM-FI Main Relay 2 (Fuel Pump) 4P Connector Terminal No. 2 And Body Ground
Is there continuity?
YES -Go to step 47.
NO -Go to step 50.
- Jump the SCS line with the HDS.
- Disconnect PCM connector C (49P).
- Check for continuity between PCM connector terminal C10 and body ground.
Is there continuity?
YES -Repair a short in the wire between the No. 2 FUEL PUMP (15 A) fuse and the PCM (C10), between the No. 2 FUEL PUMP (15 A) fuse and PGM-FI main relay 2 (FUEL PUMP), or between the No. 2 FUEL PUMP (15 A) fuse and the immobilizer control unit. Also replace the No. 2 FUEL PUMP (15 A) fuse.
NO -Replace the No. 2 FUEL PUMP (15 A) fuse, then update the PCM if it does not have the latest software (see PCM Update ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ).
- Fold the left side rear seat forward, and pull back the carpet to expose the access panel.
- Remove the access panel from the floor (see FUEL TANK UNIT REMOVAL AND INSTALLATION ).
- Disconnect the fuel pump 4P connector.
- Check for continuity between fuel pump 4P connector terminal No. 2 and body ground.
Is there continuity?
YES -Repair a short in the wire between the fuel pump and PGM-FI main relay 2 (FUEL PUMP). Also replace the No. 2 FUEL PUMP (15 A) fuse.
NO -Check the fuel pump, and replace it if needed (see FUEL PUMP/FUEL GAUGE SENDING UNIT REPLACEMENT ). Also replace the No. 2 FUEL PUMP (15 A) fuse.
- Jump the SCS line with the HDS.
- Disconnect PCM connectors A (49P) and C (49P).
- Turn the ignition switch to ON (II).
- Measure the voltage between PCM connector terminal C10 and body ground.
Is there battery voltage?
YES -Go to step 58.
NO -Repair an open in the wire between the No. 2 FUEL PUMP (15 A) fuse and the PCM (C10).
- Measure the voltage between PCM connector terminal A7 and body ground.
Is there battery voltage?
YES -Go to step 63.
NO -Go to step 59.
- Turn the ignition switch to LOCK (0).
- Remove PGM-FI main relay 1 (A) from the under-hood fuse/relay box.
- Measure the voltage between PGM-FI main relay 1 4P connector terminal No. 3 and body ground.
Is there battery voltage?
YES -Go to step 62.
NO -Replace the under-hood fuse/relay box (see REMOVAL AND INSTALLATION ).
- Check for continuity between PCM connector terminal A7 and PGM-FI main relay 1 4P connector terminal No. 4.Fig 19: Checking Continuity Between PCM Connector Terminal A7 And PGM-FI Main Relay 1 4P Connector Terminal No. 4
Is there continuity?
YES -Test PGM-FI main relay 1 (see POWER RELAY TEST ). If the relay is OK, update the PCM if it does not have the latest software (see PCM Update ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ), then recheck. If the symptom/indication goes away and the PCM was updated, troubleshooting is complete. If the symptom/indication goes away and the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ).
NO -Repair an open in the wire between the PCM (A7) and PGM-FI main relay 1.
- Turn the ignition switch to LOCK (0).
- Remove PGM-FI main relay 1 (A) from the under-hood fuse/relay box.
- Measure the voltage between PGM-FI main relay 1 4P connector terminal No. 1 and body ground.
Is there battery voltage?
YES -Go to step 66.
NO -Replace the under-hood fuse/relay box (see REMOVAL AND INSTALLATION ).
- Check for continuity between PCM connector terminal A9 and PGM-FI main relay 1 4P connector terminal No. 2.Fig 22: Checking Continuity Between PCM Connector Terminal A9 And PGM-FI Main Relay 1 4P Connector Terminal No. 2
Is there continuity?
YES -Go to step 67.
NO -Repair an open in the wire between the PCM (A9) and PGM-FI main relay 1.
- Test PGM-FI main relay 1 (see
POWER RELAY TEST
).
Is PGM-FI main relay 1 OK?
YES -Go to step 68.
NO -Replace PGM-FI main relay 1.
- Disconnect PCM connector B (49P).
- Check for continuity between body ground and PCM connector terminals B1, B10, C2, C44, and C48 individually.
NO RELATED
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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.