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.
Section 185 (Immobilizer System): Troubleshooting
- Turn the ignition switch ON (II) with a programmed key.
- Check to see if the immobilizer indicator comes on.
Does the indicator come on?
- YES - Go to step 3.
- NO - Go to step 12 .
- Check the immobilizer indicator operation.
Does the indicator come on for 2 seconds, then go off?
- YES - Go to step 4.
- NO - Go to step 6 .
- Try to crank the engine.
Does the starter motor operate?
- YES - Go to step 5.
- NO - Check the starter motor.
- Try to start the engine.
Does the engine start?
- YES - Check the Status Log in the Immobilizer Info with the HDS (see STATUS LOG ).
- NO - Go to step 27 .
- Check to see if the immobilizer indicator comes on and blinks.
Does the indicator blink?
- YES - Go to step 27 .
- NO - Go to step 7.
- Disconnect the 7P connector from the immobilizer control unit-receiver.
- Check to see if the immobilizer indicator goes off.
Does the indicator go off?
- YES - Substitute a known-good immobilizer control unit-receiver and/or PCM.
- NO - Go to step 9.
- Turn the ignition switch OFF.
- Remove the gauge control module and disconnect its connectors (see GAUGE CONTROL MODULE REPLACEMENT ).
- Check for continuity between the immobilizer control unit-receiver 7P connector No. 5 terminal and body ground.Fig 1: Checking Continuity Between Immobilizer Control Unit-Receiver 7P Connector Terminal 5 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
- YES - Repair a short in the wire.
- NO - Faulty immobilizer indicator, replace the gauge control module.
- Try to start the engine.
Does the engine start?
- YES - Go to step 13.
- NO - Go to step 19 .
- Turn the ignition switch OFF.
- Disconnect the 7P connector from the immobilizer control unit-receiver.
- Check for voltage between the immobilizer control unit-receiver 7P connector No. 7 terminal and body ground.Fig 2: Checking Voltage Between Immobilizer Control Unit-Receiver 7P Connector Terminal 7 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there battery voltage?
- YES - Go to step 16.
- NO - Faulty No. 7 (7.5 A) fuse in the driver's under-dash fuse/relay box. If the fuse is OK, check for an open in the wire between the immobilizer control unit-receiver and driver's under-dash fuse/relay box.
- Using a jumper wire, connect the immobilizer control unit-receiver No. 5 terminal to ground.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Does the indicator come on?
- YES - Replace the immobilizer control unit-receiver.
- NO - Go to step 17.
- Remove the gauge control module and disconnect its 30P connector (see GAUGE CONTROL MODULE REPLACEMENT ).
- Check for continuity between the immobilizer control unit-receiver 7P connector No. 5 terminal and gauge control module connector A (30P) No. 16 terminal.Fig 4: Checking Continuity Between Immobilizer Unit-Receiver 7P Connector Terminal 5 And Gauge Control Module Connector A (30P) Terminal 16
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
- YES - Faulty immobilizer indicator, replace the gauge control module.
- NO - Repair an open in the wire.
- Turn the ignition switch OFF.
- Disconnect the 7P connector from the immobilizer control unit-receiver.
- Turn the ignition switch ON (II).
- Check for voltage between the immobilizer control unit-receiver 7P connector No. 6 terminal and body ground.Fig 5: Checking Voltage Between Immobilizer Control Unit-Receiver 7P Connector Terminal 6 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there battery voltage?
- YES - Go to step 23.
- NO - Faulty No. 19 (15 A) fuse in the driver's under-dash fuse/relay box. If the fuse is OK, check for an open in the wire between the immobilizer control unit-receiver and driver's under-dash fuse/relay box.
- Check for voltage between the immobilizer control unit-receiver 7P connector No. 1 and No. 6 terminals.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there battery voltage?
- YES - Substitute a known-good immobilizer control unit-receiver control and recheck.
- NO - Go to step 24.
- Turn the ignition switch OFF.
- Jump the SCS line with the HDS, then disconnect PCM connector A (44P) (see HOW TO TROUBLESHOOT CIRCUITS AT THE PCM CONNECTORS ).
- Check for continuity between the immobilizer control unit-receiver 7P connector No. 1 terminal and PCM connector A (44P) No. 22 terminal.
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
- YES - Check the PCM terminals B36, B43 and C1 for poor connections to G101 and terminals B1 and C40 for poor connections to G102. If OK, substitute a known-good immobilizer control unit-receiver and recheck.
- NO - Repair an open in the wire.
- Turn the ignition switch OFF.
- Connect the HDS to the data link connector.
- Turn the ignition switch ON (II).
- Look at the System Check in the Immobilizer Info with the HDS (see SYSTEM CHECK
).
Is the immobilizer system normal?
- YES - Go back to step 1 .
- NO - Go to step 31.
- Verify the System Check display on the HDS for the following information:
- Harness short from the PCM to the immobilizer unit. (S-net line short)
- The communication was not good between the PCM and the immobilizer unit by the battery voltage low.
- The communication was not good between the immobilizer unit and the PCM by influence of some noise.
- Immobilizer unit failure
- PCM failure
Does the HDS display any of the above information?
- YES - Go to step 32.
- NO - Go to step 36 .
- Turn the ignition switch OFF.
- Disconnect the 7P connector from the immobilizer control unit-receiver.
- Jump the SCS line with the HDS, then disconnect PCM connector A (44P) (see HOW TO TROUBLESHOOT CIRCUITS AT THE PCM CONNECTORS ).
- Check for continuity between the immobilizer control unit-receiver 7P connector No. 2 terminal and body ground.Fig 8: Checking Continuity Between Immobilizer Control Unit-Receiver 7P Connector Terminal 2 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
- YES - Repair a short in the wire.
- NO - Substitute a known-good immobilizer control unit-receiver and/or PCM.
- Verify the System Check display on the HDS for the following information:
- Blown fuse
- Harness open from the PCM and the immobilizer unit.
- The communication was not good between the PCM and the immobilizer unit by battery voltage low.
- The communication was not good between the immobilizer unit and the PCM by the battery voltage low.
- The communication was not good between the immobilizer unit and the PCM by influence of some noise.
- Immobilizer unit failure
- PCM failure
Does the HDS display any of the above information?
- YES - Go to step 37.
- NO - Check the Possible Failures shown on the System Check display (see SYSTEM CHECK ).
- Turn the ignition switch OFF.
- Disconnect the 7P connector from the immobilizer control unit-receiver.
- Jump the SCS line with the HDS, then disconnect PCM connector A (44P) (see HOW TO TROUBLESHOOT CIRCUITS AT THE PCM CONNECTORS ).
- Check for continuity between the immobilizer control unit-receiver 7P connector No. 2 terminal and PCM connector A (44P) No. 44 terminal.Fig 9: Checking Continuity Between Immobilizer Control Unit-Receiver 7P Connector Terminal 2 And PCM Connector A (44P) Terminal 44
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Is there continuity?
- YES - Substitute a known-good immobilizer control unit-receiver and recheck the system. If the immobilizer control unit-receiver is OK, substitute a known-good PCM and recheck (see PCM UPDATING AND SUBSTITUTION FOR TESTING ).
- NO - Repair an open in the wire.
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.