Immobilizer System — Acura MDX II (2006-2010)

Scheme 1

Scheme 1: Component Location Index

System Description

The vehicle is equipped with an immobilizer system that will disable the vehicle unless a programmed ignition key is used.

This system consists of a transponder, a keyless transmitter, immobilizer-keyless control unit, immobilizer indicator, imoes unit (built into the MICU), and the PCM.

When the immobilizer key (programmed by the HDS) is inserted into the ignition switch and turned to the ON (II) position, the immobilizer-keyless control unit sends power to the transponder in the ignition key. The transponder then sends a coded signal back to the immobilizer-keyless control unit which then sends a coded signal to the imoes unit, which confirms the code and signals the PCM to continue to supply power to the fuel pump circuit.

Scheme 2

Scheme 2: System Description

If the wrong key has been used or the code was not received or recognized by the unit, the vehicle will not start, then shut off, and the indicator will quickly flash once, then it will blink until the ignition switch is turned to LOCK (0). When the ignition switch is turned to LOCK (0), the indicator will blink ten times to signal that the unit has reset correctly, then the indicator will go off.

Scheme 3

Scheme 3: Circuit Diagram

DTC B1905: Immobilizer-Keyless Control Unit Lost Communication with Driver's MPCS Unit (DRLOCKSW Message)

Note. If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ).

Clear the DTCs with the HDS.
Turn the ignition switch to LOCK (0), and then back ON (II).
Wait for 6 seconds or more.
Check for DTCs with the HDS. Is DTC B1905 indicated? YES - Go to step 5. NO - Intermittent failure, the system is OK at this time. Check for loose or poor connections between the immobilizer-keyless control unit and the driver's MPCS unit.
Check for DTCs with the HDS. Are DTCs B1013, B1065, B1182, and/or B1356 also indicated? YES - Do the driver's MPCS unit input test (see «DRIVER'S MPCS UNIT INPUT TEST»(/acura/mdx/ii-2006-2010/remont/communication-devices/#multiplex-integrated-control-system__drivers-mpcs-unit-input-test) ). NO - Do the immobilizer-keyless control unit input test (see «IMMOBILIZER-KEYLESS CONTROL UNIT INPUT TEST»(/acura/mdx/ii-2006-2010/remont/door-locks-anti-theft-systems/#immobilizer-system__immobilizer-keyless-control-unit-input-test) ).

DTC B1906: Immobilizer-Keyless Control Unit Lost Communication with Gauge Control Module (A/T Message)

Note. If you are troubleshooting multiple DTCs, be sure to follow the instructions in B-CAN System Diagnosis Test Mode A (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ).

Clear the DTCs with the HDS.
Turn the ignition switch to LOCK (0), and then back ON (II).
Wait for 6 seconds or more.
Check for DTCs with the HDS. Is DTC B1906 indicated? YES - Go to step 5. NO - Intermittent failure, the system is OK at this time. Check for loose or poor connections between the immobilizer-keyless control unit and the gauge control module.
Check for DTCs with the HDS. Are DTCs B1061, B1359, B1808, and B1956 also indicated? YES - Do the gauge control module input test (see «GAUGE CONTROL MODULE INPUT TEST»(/acura/mdx/ii-2006-2010/remont/gauges-instrument-panels/#gauges__gauge-control-module-input-test) ). NO - Do the immobilizer-keyless control unit input test (see «IMMOBILIZER-KEYLESS CONTROL UNIT INPUT TEST»(/acura/mdx/ii-2006-2010/remont/door-locks-anti-theft-systems/#immobilizer-system__immobilizer-keyless-control-unit-input-test) ).

General Check before Troubleshooting

Before troubleshooting the immobilizer system, check the following general items to minimize troubleshooting time

If the battery is low; fully charge the battery, then troubleshoot the immobilizer system.
The ignition key is not a genuine Acura part; use the Acura-approved key blank, register the key, then troubleshoot the immobilizer system.
Check to see if a key ring, or a key case is used; remove the immobilizer key from it, and troubleshoot the immobilizer system with the immobilizer key only.
Check to see if an aftermarket electrical part is attached; remove it, then troubleshoot the immobilizer system.

Symptom Troubleshooting Using the Immobilizer Indicator Lighting Pattern

The blinking pattern of the immobilizer indicator light can help troubleshoot the condition of the immobilizer system. Following are descriptions of the four possible patterns.

Normal operation

If the immobilizer code is identified, the immobilizer indicator comes on for a maximum of 2 seconds, then goes off after turning the ignition switch ON (II).

The immobilizer indicator does not come on when the ignition switch is turned to LOCK (0).

Immobilizer code is not identified

If the immobilizer code is not identified, the immobilizer indicator comes on for a maximum of 2 seconds, then blinks after turning the ignition switch ON (II). The immobilizer indicator blinks ten times, then goes off when the ignition switch is turned to LOCK (0).

The state of the immobilizer key registration and the IMOCD (S-NET) line can be checked by doing a SYSTEM CHECK with the HDS (see SYSTEM CHECK ).

Immobilizer indicator does not come on

If the immobilizer indicator does not come on after turning the ignition switch ON (II), an open or short in the F-CAN lines between the PCM and the gauge control module. Watch the malfunction indicator lamp (MIL). If the MIL stays on, go to the PGM-FI system troubleshooting (see GENERAL TROUBLESHOOTING INFORMATION ).

Immobilizer indicator does not go off

If the immobilizer indicator does not go off after turning the ignition switch ON (II), do the gauge control module self-diagnostic function (see SELF-DIAGNOSTIC FUNCTION ). If the indicator drive circuit is OK, do the SYSTEM CHECK with the HDS.

Symptom Troubleshooting Using Malfunctioning Circuit Functions

If a malfunction occurs in the immobilizer circuit, use the table to cross-reference the malfunctioning function to the line(s) that should be checked table

Scheme 4

Scheme 4: Symptom Troubleshooting Using Malfunctioning Circuit Functions

System Check and Status Log

Note. The HDS can be used to: Check the state of the immobilizer key registration and the IMOCD (S-NET) line by doing a SYSTEM CHECK. Check the number of times the immobilizer control unit-receiver doesn't permit the engine to run by checking the STATUS LOG. Troubleshoot the line with the highest count first.

Connect the HDS to the data link connector, then turn the ignition switch ON (II) and follow the prompts to the MAIN MENU. NOTE: If the HDS does not communicate with the vehicle, go to the DLC circuit troubleshooting (see «DLC CIRCUIT TROUBLESHOOTING»(/acura/mdx/ii-2006-2010/remont/testing-diagnostics/#pgm-fi-system__dlc-circuit-troubleshooting) ).
At the MAIN MENU, enter IMMOBILIZER, then select the IMMOBILIZER SETUP.
Do the SYSTEM CHECK. If there is a system check number, do the troubleshooting for the item indicated.
Check the status log using the HDS. Troubleshoot the line with the highest counts. If all the lines are "0" zero, the problem may not be caused by the immobilizer system, check for ignition or fuel problems. NOTE: Once repaired, clear the status log by removing the No. 7 (10 A) fuse in the under-dash fuse box or disconnecting the immobilizer control unit-receiver.

Symptom Troubleshooting Index

Troubleshoot the immobilizer system by the order of the priority shown: SYMPTOM TROUBLESHOOTING INDEX Order of Priority Symptom Possible cause 1 Immobilizer indicator blinks after the ignition switch is turned to LOCK (0). Symptom troubleshooting (see Symptom Troubleshooting «IMMOBILIZER INDICATOR BLINKS»(/acura/mdx/ii-2006-2010/remont/door-locks-anti-theft-systems/#immobilizer-system__immobilizer-indicator-blinks) ). 2 Engine does not start with the programmed immobilizer key. Symptom troubleshooting (see «ENGINE DOES NOT START WITH THE IMMOBILIZER KEY»(/acura/mdx/ii-2006-2010/remont/door-locks-anti-theft-systems/#immobilizer-system__engine-does-not-start-with-the) ). 3 Immobilizer indicator does not come on. Check the MIL indication. If the MIL comes on, go to the PGM-Fl System MIL circuit troubleshooting (see «MIL CIRCUIT TROUBLESHOOTING»(/acura/mdx/ii-2006-2010/remont/testing-diagnostics/#pgm-fi-system) ). If the MIL does not come on, replace the gauge control module. 4 Immobilizer indicator does not go off. Symptom troubleshooting (see «IMMOBILIZER INDICATOR DOES NOT GO OFF»(/acura/mdx/ii-2006-2010/remont/door-locks-anti-theft-systems/#immobilizer-system) ).

System Check

Connect the HDS to the data link connector.
Turn the ignition switch ON (II).
Monitor the System Check in the Immobilizer Info with the HDS.
If the HDS displays the "Immobilizer system is normal", the immobilizer system is OK. If the HDS displays any other messages, check as follows: SYSTEM CHECK CHART Status Log No. System Check Possible Failures A-1 Immobilizer system is not normal This key is not registered in the immobilizer-keyless control unit. Try to register keys by using "KEYS". The communication was not good between the antenna and the immobilizer key by influence of metal such as key chains. The communication was not good between the antenna and the immobilizer key by battery voltage low. A-2 Immobilizer system is not normal Intermittent interruption between transponder and immobilizer-keyless control unit. The immobilizer key type is different. It is not for this vehicle but for another one or for other company's one. Key failure (transponder failure) The communication was not good between the antenna and the immobilizer key by influence of metal such as key chains. The communication was not good between the antenna and the immobilizer key by battery voltage low. A-3 Immobilizer system is not normal The ignition switch was turned ON (II) with a non-immobilizer key. The immobilizer key type is different. It is not for this vehicle but for another one or for other company's one. Key failure (transponder failure) The communication was not good between the antenna and the immobilizer key by influence of metal such as key chains. The communication was not good between the antenna and the immobilizer key by battery voltage low. Immobilizer-keyless control unit failure B-1 Immobilizer system is not normal The PCM was not registered. Try to register the PCM by using "REPLACE PCM". The communication was not good between the PCM and the immobilizer-keyless control unit by battery voltage low. The communication was not good between the immobilizer-keyless control unit and the PCM by influence of some noise. B-2 Immobilizer system is not normal The PCM was not registered. Try to register the PCM by using "REPLACE PCM". The communication was not good between the PCM and the immobilizer-keyless control unit by battery voltage low. The communication was not good between the immobilizer-keyless control unit and the PCM by influence of some noise. D-1 Immobilizer system is not normal Harness short from the PCM to the immobilizer-keyless control unit. (IMOCD/S-NET line short) The communication was not good between the PCM and the immobilizer-keyless control unit by battery voltage low. The communication was not good between the immobilizer-keyless control unit and the PCM by influence of some noise. Immobilizer-keyless control unit failure PCM failure D-2 Immobilizer system is not normal Blown fuse Harness open from the immobilizer control unit-receiver and the imoes unit. The communication was not good between the immobilizer control unit-receiver and the imoes unit by influence of some noise. D-3 Immobilizer system is not normal Blown fuse Harness open from the PCM to the immobilizer-keyless control unit. The communication was not good between the PCM and the immobilizer-keyless control unit by battery voltage low. The communication was not good between the immobilizer-keyless control unit and the PCM by influence of some noise. Immobilizer-keyless control unit failure PCM failure

Status Log

If you suspect there is a immobilizer system problem, check the status log.

Connect the HDS to the data link connector.
Turn the ignition switch ON (II).
On the HDS screen, select Honda systems, select immobilizer set-up, select immobilizer information, then select status log.
Check the Status log count. Troubleshoot the status with the highest count first. If no counts are listed, the immobilizer system is OK. Continue with normal symptom troubleshooting. STATUS LOG CHART Status Log No. Detected Item Probable Cause A-1 KEY CODE MISMATCH (Code format normal, but code data is mismatch) The key was not registered Interference from metal such as key chains Low battery voltage A-2 KEY CODE MISMATCH (Code format failure) Ignition switch was turned ON (II) with another type of immobilizer key or aftermarket key Interference from metal such as key chains Low battery voltage A-3 KEY CODE MISMATCH (No key code or non-immobilizer key) Ignition switch was turned ON (II) with another type of immobilizer key or aftermarket key Interference from metal such as key chains Low battery voltage Key failure Immobilizer-keyless control unit failure B-1 PCM CODE MISMATCH (Code format normal, but code data is mismatch) PCM was not registered correctly Low battery voltage Poor or loose terminal connections at the immobilizer-keyless control unit Communication line electrical noise B-2 PCM MISMATCH (Code format failure) PCM was not registered correctly Low battery voltage Poor or loose terminal connections at the immobilizer-keyless control unit Communication line electrical noise D-1 IMOCD/S-NET LINE PROBLEM (Short to ground) Low battery voltage Poor or loose terminal connections at the immobilizer-keyless control unit and the PCM Communication line electrical noise D-3 IMOCD/S-NET LINE PROBLEM (Open line or PCM/immobilizer control unit-receiver failure) Open or short in the harness from the PCM to the immobilizer-keyless control unit Low battery voltage Poor or loose terminal connections at the immobilizer-keyless control unit and the PCM Communication line electrical noise

Immobilizer indicator blinks

Note. Before troubleshooting, check the items listed in "General Check before Troubleshooting".

Scheme 5

Scheme 5: Immobilizer indicator blinks

Scheme 6

Turn the ignition switch to LOCK (0).
Connect the HDS, then turn the ignition switch ON (II).
Enter the IMMOBILIZER, then select the IMMOBILIZER SETUP.
Check the SYSTEM CHECK and STATUS LOG information. Is the SYSTEM CHECK indicated? YES - Troubleshoot the immobilizer system according to the result of the SYSTEM CHECK/ STATUS LOG (see «SYSTEM CHECK»(/acura/mdx/ii-2006-2010/remont/door-locks-anti-theft-systems/#immobilizer-system__system-check) ). NO - Go to step 5.
Turn the ignition switch to LOCK (0).
Enter the vehicle, and remove the ignition key from the ignition switch, then close the all doors.
Operate the keyless transmitter LOCK and UNLOCK several times in the vehicle. Do the door lock actuators work normally? YES - Go to step 8. NO - Check for a poor ground (G101) and/or an open in the wire between the immobilizer-keyless control unit 7P connector No. 7 terminal and PCM connector A (49P) No. 41 terminal.
Turn the ignition switch ON (II).
Measure the voltage between the immobilizer-keyless control unit 7P connector No. 2 terminal and body ground. Is there battery voltage? YES - Go to step 10. NO - Check No. 19 (20 A) fuse in the under-dash fuse/relay box or for an open in the BRN wire between the under-dash fuse-relay box and the immobilizer-keyless control unit.
Measure the voltage between the immobilizer-keyless control unit 7P connector No. 7 terminal and body ground. Is there less than 0.5 V? YES - Replace the immobilizer-keyless control unit. NO - Check for a poor ground (G101) and/or repair poor connection or open between the immobilizer-keyless control unit 7P connector No. 7 terminal and PCM connector A (49P) No. 41 terminal.

Engine does not start with the immobilizer key

Note. Before troubleshooting, check the items listed in "General Check before Troubleshooting" and "How to Troubleshoot" (see GENERAL CHECK BEFORE TROUBLESHOOTING ).

Try to start the engine. Does the engine start? YES - Intermittent failure, the vehicle is OK at this time. Check status log (see «STATUS LOG»(/acura/mdx/ii-2006-2010/remont/door-locks-anti-theft-systems/#immobilizer-system__status-log) ). NO - Go to step 2.
Turn the ignition switch to LOCK (0).
Turn the ignition switch ON (II), and check the immobilizer indicator indication. Does the indicator quickly flash twice and turn off? YES - Go to step 4. NO - Do the immobilizer-keyless control unit input test (see «IMMOBILIZER-KEYLESS CONTROL UNIT INPUT TEST»(/acura/mdx/ii-2006-2010/remont/door-locks-anti-theft-systems/#immobilizer-system__immobilizer-keyless-control-unit-input-test) ).
Turn the ignition switch to START (III). Does the starter crank the engine? YES - Go to step 5. NO - Go to Starting System troubleshooting and check the starter motor circuit.
Try to start the engine with a different known-good immobilizer key (previously programmed and known to start the vehicle). Does the engine start? YES - Replace the immobilizer key. NO - Go to the PGM-FI System Symptom Troubleshooting.

Turn the ignition switch to LOCK (0).
Connect the HDS to the data link connector.
Turn the ignition switch ON (II).
Enter the IMMOBILIZER, then select the IMMOBILIZER INFORMATION.
Do the SYSTEM CHECK with the HDS. Is N-1 OK indicated? YES - Do the gauge control module self-test. If the gauge control module is faulty, replace it. NO - Substitute a known-good immobilizer-keyless control unit, then register it and recheck. If the symptom goes away, replace the original immobilizer-keyless control unit.

Immobilizer Key Registration

Note. The HDS is required for registration of the immobilizer keys. Check for aftermarket electrical equipment that can cause problems with transponder operation. The immobilizer-keyless control unit can store up to six immobilizer Keys.

Add one new key

Have a registered key, a new immobilizer key, and the first password from the iN system.
Connect the HDS to the data link connector.
Turn the ignition switch ON (II).
Select "IMMOBILIZER" from the "SYSTEM SELECT" menu.
Select "Add and Delete Keys", then "Add 1 key".
Do the registration according to the instructions on the HDS screen.
Check if the engine can be started by the newly registered key. Check the keyless remote operation to make sure that it functions properly.

Delete or add multiple keys

Note. If any of the registered keys were lost, do the following procedure to delete the lost registered key. When deleting keys, it is necessary to delete all stored remote transmitters. Refer to the keyless transmitter programming to delete and reprogram the remote (see TRANSMITTER TEST/REPLACEMENT ).

Have all registered keys, all new keys, and the first password.
Connect the HDS to the data link connector.
Turn the ignition switch ON (II).
Select "IMMOBILIZER" from the "SYSTEM SELECT" menu.
Select "Add and Delete Keys", or "Delete or Add Multiple Keys".
Do the registration according to the instruction of HDS screen.
Check if the engine can be started by all the registered keys.

All keys are lost

Note. When deleting keys, it is necessary to delete all stored remote transmitters. Refer to the keyless transmitter programming to delete and reprogram the remote (see TRANSMITTER TEST/REPLACEMENT ).

Prepare all new keys and have the immobilizer PCM code.
Connect the HDS to the data link connector.
Turn the ignition switch ON (II).
Select "IMMOBILIZER" from the "SYSTEM SELECT" menu.
Select "Add and Delete Keys", then "ALL KEYS LOST".
Do the registration according to the instruction of HDS screen.
Check if the engine can be started by all the registered keys.

Immobilizer-keyless Control Unit Input Test

Note. Before testing the immobilizer-keyless control unit, troubleshoot the multiplex integrated control unit first, using B-CAN System Diagnosis Test Mode A (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ) and check the No. 19 (20 A) and No. 7 (10 A) fuses in the under-dash fuse/relay box.

Scheme 7

Scheme 7: Immobilizer-keyless Control Unit Input Test

Remove the steering column covers (see «COLUMN COVER REMOVAL/INSTALLATION»(/acura/mdx/ii-2006-2010/remont/exteriorinterior-trim/#dashboard__column-cover-removalinstallation) ).
Disconnect the 7P connector (A) from the immobilizer-keyless control unit (B).
Inspect the connector and socket terminals to be sure they are all making good contact. If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system. If the terminals look OK, go to step 4.
With the connector still disconnected, make these input tests at the connector. If any test indicates a problem, find and correct the cause, then recheck the system. If all the input tests prove OK, go to step 5. IMMOBILIZER-KEYLESS CONTROL UNIT INPUT Cavity Wire Test condition Test: Desired result Possible cause if desired result is not obtained 3 LT GRN (IMOCD (S-NET)) Immobilizer-keyless control unit 7P connector, the PCM connector A (49P), and the under-dash fuse/ relay box connector Q (14P) disconnected. Check for continuity between the No. 3 terminal and the PCM connector A (49P) No. 46 terminal: There should be continuity. An open in the wire Check for continuity between the No. 3 terminal and under-dash fuse/relay box connector Q (14P) No. 9 terminal: There should be continuity. Check for continuity to body ground: There should be no continuity. A short to ground in the wire 4 LT GRN (B-CAN) Immobilizer-keyless control unit 7P connector, the under-dash fuse/ relay box connector X(39P) disconnected. Check for continuity between the No. 4 terminal and under-dash fuse/relay box connector X (39P) No. 27 terminal: There should be continuity. An open in the wire Check for continuity to body ground: There should be no continuity. A short to ground in the wire 5 LT BLU (K-LINE) Immobilizer-keyless control unit 7P connector disconnected. Check for continuity between the No. 5 terminal and the data link connector (16P) Non terminal: There should be continuity. An open in the wire Check for continuity to body ground: There should be no continuity. A short to ground in the wire
Reconnect the connector to the immobilizer-keyless control unit, and make these input tests at the connector. If any test indicates a problem, find and correct the cause, then recheck the system. If all the input tests prove OK, the immobilizer-keyless control unit must be faulty; replace it. IMMOBILIZER-KEYLESS CONTROL UNIT INPUT Cavity Wire Test condition Test: Desired result Possible cause if desired result is not obtained 1 WHT (VBU) Under all conditions Measure the voltage to body ground: There should be battery voltage. Blown No. 7 (10 A) fuse in the under-dash fuse/relay box An open in the wire 2 BRN (IG1) Ignition switch ON (II) Measure the voltage to ground: There should be battery voltage. Blown No. 19 (20 A) fuse in the under-dash fuse/relay box An open in the wire 7 BRN (LG3) Under all conditions Measure the voltage to ground: There should be less than 0.5 V. Poor ground (G101) An open in the wire Faulty PCM 6 PNK (IG KEY SW) Ignition key inserted into the ignition switch Measure the voltage to ground: There should be less than 0.5 V. Poor ground (G601) Faulty ignition key switch An open in the wire

Immobilizer-keyless Control Unit Replacement

Note. All registered keys are necessary for replacement of the immobilizer-keyless control unit.

Scheme 8

Scheme 8: Immobilizer-keyless Control Unit Replacement

Remove the driver's dashboard lower cover (see «DRIVER'S DASHBOARD LOWER COVER REMOVAL/INSTALLATION»(/acura/mdx/ii-2006-2010/remont/exteriorinterior-trim/#dashboard) ).
Remove the steering column covers (see «COLUMN COVER REMOVAL/INSTALLATION»(/acura/mdx/ii-2006-2010/remont/exteriorinterior-trim/#dashboard__column-cover-removalinstallation) ).
Disconnect the 7P connector (A) from the immobilizer-keyless control unit (B).
Remove the two screws and the immobilizer-keyless control unit from the ignition key cylinder.
Install the immobilizer-keyless control unit in the reverse order of removal.
After replacement, turn the ignition switch ON (II).
Connect the HDS to the data link connector.
Select "IMMOBI" from the "System Select" menu.
Select "Immobilizer Setup" from the "Mode Menu".
Select "Replace Imm Unit".
Operate according to instructions of a screen of HDS.
After HDS operation, check the immobilizer system.
Verify the operation of every key and remote transmitter.

Immobilizer System Acura MDX II