SECTION : 9T

IMMOBILIZER ANTI–THEFT SYSTEM

CAUTION : Disconnect the negative battery cable before removing or installing any electrical unit or when a tool
or equipment could easily come in contact with exposed electrical terminals. Disconnecting this cable will help
prevent personal injury and damage to the vehicle. The ignition must also be in LOCK unless otherwise noted.

TABLE OF CONTENTS
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . 9T–1 ID CODE REPROGRAMMING . . . . . . . . . . . . . . 9T–4
FASTENER TIGHTENING TRANSPONDER . . . . . . . . . . . . . . . . . . . . . . . . . . 9T–5
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . 9T–1 DETECTION COIL . . . . . . . . . . . . . . . . . . . . . . . . . 9T–5
SPECIAL TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . 9T–1 IMMOBILIZER CONTROL UNIT . . . . . . . . . . . . . 9T–8
SPECIAL TOOLS TABLE . . . . . . . . . . . . . . . . . . . 9T–1
GENERAL DESCRIPTION AND SYSTEM
DIAGNOSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9T–2 OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9T–10
IMMOBILIZERANTI–THEFT SYSTEM . . . . . . . 9T–2 IMMOBILIZER SYSTEM . . . . . . . . . . . . . . . . . . 9T–10
DTC 53 – PCM/ECM Immobilized Error . . . . . . . 9T–2 ELECTRONICALLY CODED KEYS . . . . . . . . . 9T–10
KEY STATUS ERRORS . . . . . . . . . . . . . . . . . . . . 9T–2 DETECTION COIL . . . . . . . . . . . . . . . . . . . . . . . . 9T–10
COMMUNICATION BETWEEN IMMOBILIZER CONTROL UNIT . . . . . . . . . . . . 9T–10
IMMOBILIZER AND TEST EQUIPMENT . . . . 9T–3
SERIAL DATA LINK . . . . . . . . . . . . . . . . . . . . . . . . 9T–11
MAINTENANCE AND REPAIR . . . . . . . . . . . . . . . 9T–4
POWERTRAIN CONTROL MODULE
ON–VEHICLE SERVICE . . . . . . . . . . . . . . . . . . . . . 9T–4 (PCM)/ENGINE CONTROL
KEY CODING PROCEDURE . . . . . . . . . . . . . . . 9T–4 MODULE (ECM) . . . . . . . . . . . . . . . . . . . . . . . . . 9T–11

SPECIFICATIONS
FASTENER TIGHTENING SPECIFICATIONS
Application NSm Lb–Ft Lb–In
Immobilizer Control Unit Mounting Bolts 4 – 35
Knee Bolster Mounting Bolts 22 16 –

SPECIAL TOOLS
SPECIAL TOOLS TABLE

Scan Tool
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Unauthorized use of a scan tool could be a method of de-

feating the immobilizer anti–theft system. Therefore, cer-
DIAGNOSIS tain scan tool procedures require the use of a password.
The following functions are password protected:

S Coding of an additional key.

S Deleting all key codes.
IMMOBILIZERANTI–THEFT SYSTEM S Deletion of the immobilizer identification (ID) code.
The immobilizer anti–theft system requires diagnosis S Deletion of the powertrain control module
when it is not possible to start the engine. If the no–start (PCM)/engine control module (ECM) ID code.
condition occurs because of the immobilizer system, a
diagnostic trouble code (DTC) 53 should be set. The following functions do not require a password:

S Reading an ignition key to determine if the trans-

The immobilizer anti–theft system requires diagnosis
ponder is working or if a key is authorized.
when it is not possible to start the engine. If the no–start
S Reading the immobilizer ID code to verify that it
condition occurs because of the immobilizer system, a
matches the PCM/ECM ID code.
diagnostic trouble code (DTC) 53 should be set.

DTC 53 – PCM/ECM Immobilized Error

Step Action Value(s) Yes No

1 Connect the scan tool using the following procedure: Go to Step 2 Go to ”Commu-
1. Insert the immobilizer data cartridge into the nication Be-
scan tool. tween Immobi-
2. Turn the ignition OFF. lizer and Test
3. Connect the scan tool to the data link connec- Equipment”
tor DLC).
4. Turn the ignition ON, but do not start the en-
gine.
Is communication established between the scan tool
and the immobilizer control unit?
2 Select SYSTEM DIAGNOSIS from the scan tool Go to ’Key Go to Step 3
menu. Status Errors”
Does the KEY STATUS message indicate POS NR
(position number) 00?
3 Read the IMMO & PCM/ECM ID–CODE message Go to ”ID Go to Step 4
that is displayed after requesting SYSTEM DIAG- Code Repro-
NOSIS. gramming”
Does the message ID–CODE DIFFERENT appear?
4 Check for an open serial data wire between the im- Go to Step 5 Go to Step 6
mobilizer control unit and the powertrain control
module (PCM)/engine control module (ECM).
Is the circuit open?
5 Repair the open serial data wire between the PCM/ System OK
ECM and the immobilizer control unit.
Is the repair complete?
6 1. Replace the ECM. System OK
2. Reprogram the identification (ID) code. Refer
to”ID Code Reprogramming” in this section.
Is the repair complete?

S IGNITION OFF STATUS. This message informs

KEY STATUS ERRORS the technician that the ignition is OFF during the
The following KEY STATUS messages may be shown on key coding process. Turn the ignition ON during key
the scan tool after commanding SYSTEM DIAGNOSIS: coding, but do not start the engine.

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S KEY IS OCCUPIED. Only five keys may be coded. 1. Try a different key. If a different key works, the
If a new key is desired, the previous key codes problem is in the original key.
must be deleted. Up to five keys may then be au- 2. If trying a different key results in the same error
thorized. message, check the connection of the detection
S ALREADY AUTHORIZED. Key coding is being at- coil.
tempted with a key that is already authorized. 3. If the connection of the detection coil is okay, dis-
S ERROR NO. 001, 002, 003. There is no commu- connect the detection coil and use an ohmmeter to
nication between the transponder in the ignition key check for an open detection coil.
and the detection coil. Follow the steps below to 4. If the detection coil is not open, replace the immobi-
diagnose the problem: lizer control unit. Refer to”Immobilizer Control Unit”
1. Try a different key. If a different key works, the in this section.
problem is in the original key.
2. If trying a different key results in the same error COMMUNICATION BETWEEN
message, replace the detection coil. IMMOBILIZER AND TEST
S INVALID KEY. The communication between the EQUIPMENT
immobilizer control unit and the key transponder
has not validated the key. Follow the steps below to 1. Connect the test equipment as described in theS-
diagnose the problem: can Tool Equipment Manual.
2. If communication between the scan tool and the
1. Code the key. Refer to”Key Coding Procedure”in test equipment is unsuccessful, wait 30 seconds
this section. and try again.
2. If the same message is received after key coding, 3. If communication is not successful on the second
check the connection of the detection coil. try, turn the ignition OFF, and check the wire and
3. If the detection coil is okay, replace the immobilizer. the connectors between the immobilizer control unit
Refer to”Immobilizer Control Unit” in this section. terminal 3 and the data link connector (DLC).
S NO TRANSPONDER DETECTED. The fault may 4. If the wire and the connectors between the DLC
be in ignition key transponder, the detection coil, or and the immobilizer control unit are OK, replace the
the immobilizer. Follow the steps below to diagnose immobilizer control unit. Refer to ”Immobilizer Con-
the problem: trol Unit”in this section.

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MAINTENANCE AND REPAIR

ON–VEHICLE SERVICE
KEY CODING PROCEDURE
1. Install the immobilizer control unit cartridge in the
scan tool.
2. Turn the ignition OFF
3. Connect the scan tool.
4. Turn the ignition ON with the key to be coded.
5. Enter the four–digit password that enables service
personnel to use the scan tool for coding keys.
6. A lost key can be deleted only by deleting all keys
and reauthorizing the remaining keys as new keys.
If a key is lost, go to the next step. If no keys have
been lost but an additional key is desired, go to
Step 8.
7. Use the scan tool command DELETE ALL KEY
CODES.
8. Use the scan tool command AUTHORIZE ONE
ADDITIONAL KEY.
9. Repeat Steps 4, 5, and 6 until the immobilizer con-
trol unit has recorded all of the new keys or, after a
deletion, has reauthorized all of the remaining keys.
The immobilizer control unit can record a maximum
of five keys.
10. Return the system to the normal mode.
11. Turn the ignition OFF.
12. Turn the ignition ON.
13. Start the engine.
ID CODE REPROGRAMMING
Reprogram the identification (ID) code in the following si-
tuations:
1. An immobilizer control unit has been replaced.
2. An electronic control module (ECM) has been re-
placed.
If a valid key has been lost, refer to”Key Coding Proce-
dure” in this section.
Reprogramming Procedure

1. Turn the ignition OFF. Reprogramming is not al-

lowed while the engine is running.
2. Insert the immobilizer control unit cartridge into the
scan tool.
3. Turn the ignition ON, but do not start the vehicle.
4. Enter the four–digit password that enables service
personnel to use the scan tool for ID code repro-
gramming.
5. Use the scan tool to command RESET ID CODE.

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6. Turn the ignition OFF and ON again, but do not

crank or start the engine. The powertrain control
module (PCM)/engine control module (ECM) will
reset the ECM ID code to match the new ID code
that was calculated and sent by the immobilizer
control unit when the ignition was first turned ON
after the reset command.
7. Return the system to the normal mode.
8. Turn the ignition OFF.
9. Turn the ignition ON.
10. Start the engine.
After reprogramming the ID code, the scan tool SYSTEM
DIAGNOSIS command can verify that the PCM/ ECM ID
code matches the immobilizer control unit ID code.

If the reprogramming procedure does not result in match-

ing ID codes, check the electrical connectors for the serial
data wire between the immobilizer control unit and the
PCM/ECM.

TRANSPONDER
If a transponder is faulty, the ignition key must be replaced.
It is not possible to install a new transponder into a key.

DETECTION COIL
Removal Procedure

1. Carefully pull the knee bolster trim panel until it is

loose from its retaining clips.

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2. Slide the knee bolster trim panel upward and pull it

outward to remove it.
3. Remove the instrument panel side cover.

4. Remove the bolts and the knee bolster.

5. Remove the steering column lower cover. Refer

toSection 6E, Steering Wheel and Column.
6. Disconnect the two–pin connector from the immobi-
lizer.

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 IMMOBILIZER ANTI–THEFT SYSTEM 9T – 7

7. Pry the detection coil away from the lock cylinder. If

the detection coil will be replaced with a new one, it
does not matter if the key position trim ring is dam-
aged during removal. A new trim ring is part of the
new detection coil.

Installation Procedure

1. Install the detection coil by pressing it onto the lock

cylinder until it snaps in place.
2. Connect the two–pin connector to the immobilizer.
3. Install the steering column lower cover. Refer to
Section 6E, Steering Wheel and Column.
4. Install the knee bolster with the bolts.
Tighten
Tighten the knee bolster mounting bolts to 22 NSm (16
lb–ft)

5. Install the instrument panel side cover.

6. Install the knee bolster trim panel.

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IMMOBILIZER CONTROL UNIT

Removal Procedure

1. Disconnect the negative battery cable.

2. Carefully pull the knee bolster trim panel loose from
its retaining clips.

3. Slide the knee bolster trim panel upward and pull it

outward to remove it.
4. Remove the instrument panel side cover.

5. Remove the bolts and the knee bolster.

6. Remove the bolts and the immobilizer control unit.
7. Disconnect the electrical connectors from the im-
mobilizer control unit.

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Installation Procedure

1. Connect the electrical connectors to the immobilizer

control unit.
2. Install the immobilizer control unit with the bolts.
Tighten
Tighten the immobilizer control unit mounting bolts to
4 NSm (35 lb–in).

3. Install the knee bolster with the bolts.

Tighten
Tighten the knee bolster mounting bolts to 22 NSm (16
lb–in).
4. Install the instrument panel side cover.
5. Install the knee bolster trim panel.
6. Connect the negative battery cable.
Important : After replacing the immobilizer, the keys must
be re–authorized using the key coding procedure. Refer
to”Key Coding Procedure” in this section. Also, the elec-
tronic control module (ECM) identification (ID) code must
be reset. Refer to”ID Code Reprogramming” in this sec-
tion.

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9T – 10IIMMOBILIZER ANTI–THEFT SYSTEM

the radio–frequency signal. A release message is sent to

GENERAL DESCRIPTION the powertrain control module (PCM)/engine control mod-
ule (ECM) if the key is authorized.
AND SYSTEM OPERATION New keys are coded by using a scan tool. Refer to in this
section.”Key Coding Procedure”
IMMOBILIZER SYSTEM DETECTION COIL
The purpose of the immobilizer system is to prevent the
A detection coil is mounted at the ignition lock as an inte-
vehicle from being stolen or driven by unauthorized users.
gral part of the key position trim ring. The wires to and from
Users are authorized by an electronically coded key.
the detection coil are connected to the immobilizer. When
When the ignition is turned ON, the key is tested by the im- the ignition is turned ON, the immobilizer energizes the
mobilizer system. While the key code is being read by the detection coil and the coil is coupled inductively to the
immobilizer control unit, the engine can start and run with transponder in the ignition key. The immobilizer sends a
any key that will turn the lock cylinder. The key code is read modulated signal to the detection coil. The signal is
and compared with key codes that have been stored in the changed by interaction with the internal transponder in the
immobilizer control unit’s memory. ignition key. The immobilizer reads the signal from the
If a valid key is detected, the immobilizer control unit sends detection coil and determines whether the key is autho-
a serial data release message to the powertrain control rized.
module (PCM)/engine control module (ECM). Included in
the release message is an identification (ID) code which IMMOBILIZER CONTROL UNIT
assures that neither the immobilizer control unit nor the The immobilizer control unit is an electronic module in the
PCM/ECM has been substituted to defeat the system. instrument panel which verifies the validity of an ignition
key when the ignition is turned ON.
If the PCM/ECM does not receive a release message with-
in a specified time, or if the ID codes do not match, the To accomplish its purpose, the immobilizer control unit
PCM/ECM performs the following actions: performs the following actions:
S Disables the fuel injector circuit. S Learns and stores the codes of valid keys.
S Disables the fuel pump circuit. S Reads the radio frequency input from the ignition
S Disables the ignition coil. key.
S Sets diagnostic trouble code (DTC) 53. S Compares the received code with the codes of the
valid keys.
The above conditions are maintained until the ignition is
S Sends a release message to the powertrain control
turned OFF.
module (PCM)/engine control module (ECM) if a
The immobilizer control unit system consists of the follow- valid key has been presented.
ing components: S Calculates and transmits identification (ID) codes
within each release message.
S Electronically coded keys.
S Controls the external relay which interrupts the
S Detection coil.
starter relay circuit.
S Immobilizer control unit.
S Controls the status indicator in the instrument clus-
S PCM/ECM.
ter.
S Instrument cluster indicator.
S Monitors system faults.
S A data link connector (DLC) to provide serial data
S Supports system test functions.
access for a scan tool.
A PCM/ECM for a vehicle without an immobilizer control Normal Operation
unit cannot be interchanged with a PCM/ECM that is used When the ignition is turned ON, the immobilizer control
with an immobilizer control unit system. The immobilizer unit tries to read the key code transmitted by the trans-
control unit and the PCM/ECM must have a matching ID ponder in the ignition key.
code. ID coding and key coding are accomplished by using
a scan tool. If a valid key is detected, the immobilizer control unit sends
a release message to the PCM/ECM. The release mes-
sage contains an ID code. Immobilization will be per-
ELECTRONICALLY CODED KEYS formed by the PCM/ECM if no release message is re-
Each valid ignition key has an internal transponder which ceived, or if the ID code in the PCM/ECM does not match
transmits a unique code. When a key is inserted into the the immobilizer control unit ID code.
ignition lock, the transponder is inductively coupled to the
detection coil. The transponder interacts with the detec- If a non–valid key is detected, the release message is not
tion coil to generate an amplitude modulated modulated sent to the PCM/ECM.
signal which is conducted from the detection coil to the im- When the driver turns the ignition OFF, the immobilizer
mobilizer control unit. The immobilizer control unit reads control unit switches to the active mode.

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trol module (ECM) detects that the ignition is being turned

Data Link Connector (DLC) ON, the PCM/ECM waits for a release message from the
When the ignition is ON, a scan tool can switch the immo- immobilizer control unit. If a release message is not re-
bilizer control unit to the data link connector (DLC) mode ceived within a specified time, the PCM/ECM disables the
for the purpose of diagnostics, key coding, or ID coding. engine. The engine is also disabled if the identification (ID)
code transmitted by the immobilizer control unit does not
ID Code Handling match the code stored in the PCM/ECM’s memory. Immo-
One of 65,535 possible ID codes is stored in the immobiliz- bilization remains in effect until the ignition is turned OFF,
er control unit’s memory. or until battery power is removed.
The ID code can be erased by using the scan tools’RESET
To prevent the vehicle from being driven, the PCM/ECM
ID CODE command. When the immobilizer control unit
applies the following strategy:
calculates a new ID code, the PCM/ECM ID code must be
reset to match the immobilizer control unit ID code. To re- S The ignition module is put in a bypass mode.
set the ID code, refer to ”ID Code Reprogramming.” S The PCM/ECM will not create an electronic spark
During diagnostic procedures, the ID code can be read for timing (EST) output. Therefore, no spark will be
comparison with the PCM/ECM ID code by using the scan generated by the ignition coil.
tool’s READ IMMOBILIZER CONTROL UNIT IDCODE S The PCM/ECM will not enable the fuel pump.
command. S The PCM/ECM will not enable the fuel injectors.
S The PCM/ECM sets diagnostic trouble code (DTC)
SERIAL DATA LINK 53.
Serial data can be exchanged between a scan tool, the Serial data communication is transmitted on a single wire
powertrain control module (PCM)/engine control module between the immobilizer control unit and the PCM/ ECM.
ECM), and the immobilizer control unit.
The scan tool connection is the data link connector (DLC). During diagnostic procedures or ID code changing, a scan
tool is added to the communication system.
POWERTRAIN CONTROL MODULE A PCM/ECM with an immobilizer control unit is not ex-
(PCM)/ENGINE CONTROL MODULE changeable with a PCM/ECM that does not have an immo-
(ECM) bilizer control unit.
When the powertrain control module (PCM)/engine con-

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