DAEWOO LACETTI 2004 Service Repair Manual

SECTION : 9T2
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
SCHEMATIC AND ROUTING DIAGRAMS9T2–2 . . . .
Immobilizer Anti–Theft System 9T2–2. . . . . . . . . . . . .
DIAGNOSTIC INFORMATION AND
PROCEDURES9T2–3 . . . . . . . . . . . . . . . . . . . . . . . . . .
Immobilizer System
(MR–140, HV–240, SIRIUS D4) 9T2–3. . . . . . . . . . .
Diagnostic Trouble Code (DTC) P1626 (MR–140,
HV–240), P1628 (SIRIUS) 9T2–4. . . . . . . . . . . . . . .
Diagnostic Trouble Code (DTC) P1631 (MR–140,
HV–240), P1629 (SIRIUS D4) 9T2–6. . . . . . . . . . . .
Key Status Errors
(MR–140, HV–240, SIRIUS D4) 9T2–8. . . . . . . . . . .
Communication Between Immobilizer Control Unit and
Test Equipment
(MR–140, HV–240, SIRIUS D4) 9T2–8. . . . . . . . . . . MAINTENANCE AND REPAIR9T2–9 . . . . . . . . . . . . . .
ON–VEHICLE SERVICE 9T2–9. . . . . . . . . . . . . . . . . . . .
Key Coding Procedure 9T2–9. . . . . . . . . . . . . . . . . . . .
ID Code Reprogramming 9T2–9. . . . . . . . . . . . . . . . . .
Transponder 9T2–9. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Immobilizer Control Unit 9T2–9. . . . . . . . . . . . . . . . . . .
GENERAL DESCRIPTION AND SYSTEM
OPERATION9T2–11 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Immobilizer System 9T2–11. . . . . . . . . . . . . . . . . . . . . .
Electronically Coded Keys 9T2–11. . . . . . . . . . . . . . . .
Detection Coil 9T2–11. . . . . . . . . . . . . . . . . . . . . . . . . . .
Immobilizer Control Unit 9T2–11. . . . . . . . . . . . . . . . . .
Serial Data Link 9T2–12. . . . . . . . . . . . . . . . . . . . . . . . .
Electronic Control Moudle (ECM) 9T2–12. . . . . . . . . .

9T2 – 2IIMMOBILIZER ANTI–THEFT SYSTEM
DAEWOO V–121 BL4
SCHEMATIC AND ROUTING DIAGRAMS
IMMOBILIZER ANTI–THEFT SYSTEM

IMMOBILIZER ANTI–THEFT SYSTEM 9T2 – 3
DAEWOO V–121 BL4
DIAGNOSTIC INFORMATION AND
PROCEDURES
IMMOBILIZER SYSTEM (MR–140,
HV–240, SIRIUS D4)
The immobilizer anti–theft system requires diagnosis
when it is not possible to start the engine. If the no–start
condition occurs because of the immobilizer system, a
diagnostic trouble code (P) 1626, 1628, 1629, 1631 should
be set.
The immobilizer control unit monitors the detection and
the reading of the ignition key. The self–test capacity is lim-
ited to those functions. Faults are communicated to a scan
tool during diagnosis, but they are not stored in the immo-
bilizer control unit’s memory.Unauthorized use of a scan tool could be a method of de-
feating the immobilizer anti–theft system, so certain scan
tool procedures require the use of a password. The follow-
ing functions are password protected:
S Coding of an additional key.
S Deleting all key codes.
The following functions do not require a password:
S Reading an ignition key to determine if the trans-
ponder is working or if a key is authorized.
S Reading the immobilizer ID code to verify that it
matches the ECM ID code.

9T2 – 4IIMMOBILIZER ANTI–THEFT SYSTEM
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P1626 (MR–140,
HV–240), P1628 (SIRIUS)
ECM IMMOBILIZER ERROR (NO SUCCESSFUL
COMMUNICATION)
Circuit Description
When the ignition is turned ON, the key is tested by the im-
mobilizer anti–theft system. While the key code is being
read by the immobilizer control unit, the engine can start
and run with any key that will turn the lock cylinder. The key
code is read and compared with key codes that have been
stored in the memory of the immobilizer control unit. If a
valid key is detected, the immobilizer control unit sends a
serial data release message to the electronic control mod-
ule (ECM). Included in the release message is an identifi-
cation (ID) code which assures that neither the immobiliz-
er control unit nor the ECM has been substituted to defeatthe system. If the ECM receives an invalid release mes-
sage, the ECM performs the following actions:
S Disables the fuel injector circuit.
P1626, 1628 Will Set When
S The ECM does not receive the signal from the im-
mobilizer control module within 1.260 seconds after
the ignition is turned on.
S The above conditions are maintained until the igni-
tion is switched OFF.
P1626, 1628 Will Clear When
S The ignition switch is turned OFF or the scan tool
TROUBLE CODE CLEAR command is issued.

IMMOBILIZER ANTI–THEFT SYSTEM 9T2 – 5
DAEWOO V–121 BL4
P1626, 1628 – ECM Immobilizer Error
(No Successful Communication)
StepActionValue(s)YesNo
1Connect the scan tool using the following procedure:
1. Insert the cartridge into the scan tool.
2. Turn the ignition switch to the OFF position.
3. Connect the scan tool to the data link connec-
tor (DLC).
4. Connect the scan tool’s power cord to the cigar
lighter socket.
5. Select immobilizer mode on the scan tool.
6. Turn the ignition ON, but do not start the en-
gine.
Is communication established between the scan tool
and the immobilizer control unit?–Go to Step 2Go to ”Commu-
nication Be-
tween Immobi-
lizer and Test
Equipment”
2Read the IMMO & ECM ID CODE message that was
displayed after requesting DIAGNOSIS.
Did the message differ from normal message?
Normal Message –
ECM MODE: LEARNT
IMMO. MODE: LEARNT
VIN CODE: SAME–Go to ”Identifi-
cation (ID)
Code Repro–
gramming”Go to Step 3
3Check for an open serial data wire between the im-
mobilizer control unit and the ECM.
Was the circuit open?–Go to Step 4Go to Step 5
4Repair the open serial data wire between the ECM
and the immobilizer control unit.
Is the repair complete?–System OK–
51. Replace the immobilizer.
2. Reprogram the identification (ID) code. Refer
to ”Identification (ID) Code Reprogramming” in
this section.
Is the repair complete?–System OKGo to Step 6
61. Replace the ECM.
2. Turn the ignition ON, OFF for more than 4 sec-
onds.
3. Turn the ignition ON.
Is the repair complete?–System OK–

9T2 – 6IIMMOBILIZER ANTI–THEFT SYSTEM
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P1631 (MR–140,
HV–240), P1629 (SIRIUS D4)
ECM IMMOBILIZER ERROR (INCORRECT ANSWER)
Circuit Description
When the ignition is turned ON, the key is tested by the im-
mobilizer anti–theft system. While the key code is being
read by the immobilizer control unit, the engine can start
and run with any key that will turn the lock cylinder. The key
code is read and compared with key codes that have been
stored in the memory of the immobilizer control unit. If a
valid key is detected, the immobilizer control unit sends a
serial data release message to the electronic control mod-
ule (ECM). Included in the release message is an identifi-
cation (ID) code which assures that neither the immobiliz-er control unit nor the ECM has been substituted to defeat
the system. If the ECM receives an invalid release mes-
sage, the ECM performs the following actions:
S Disables the fuel injector circuit.
P1631, 1629 Will Set When
S The ECM receives an incorrect release message
from the immobilizer control unit more than five
times.
P1631, 1629 Will Clear When
S The ignition switch is turned OFF or the scan tool
TROUBLE CODE CLEAR command is issued.

IMMOBILIZER ANTI–THEFT SYSTEM 9T2 – 7
DAEWOO V–121 BL4
P1631, 1629 – ECM Immobilizer Error (Incorrect Answer)
StepActionValue(s)YesNo
1Connect the scan tool using the following procedure:
1. Insert the cartridge into the scan tool.
2. Turn the ignition switch to the OFF.
3. Connect the scan tool to the data link connec-
tor (DLC).
4. Connect the scan tool’s power cord to the cigar
lighter socket.
5. Turn the ignition ON, but do not start the en-
gine.
Is communication established between the scan tool
and the immobilizer control unit?–Go to Step 2Go to ”Commu-
nication Be-
tween Immobi-
lizer and Test
Equipment”
21. Select DIAGNOSIS from the scan tool menu.
2. Read the IMMO & ECM ID CODE (immobiliza-
tion and electronic control module identification
code) message.
Did the message differ from normal message?
Normal Message –
ECM MODE:LEARNT
IMMO. MODE: LEARNT
VIN CODE: SAME–Go to ”Identifi-
cation (ID)
Code Repro–
gramming”Go to Step 3
31. Replace the ECM.
2. Reprogram the ID code.
Is the repair complete?–System OKGo to Step 4
41. Replace the ECM.
2. Turn the ignition ON, OFF for more than 4 sec-
onds.
3. Turn the ignition ON.
Is the repair complete?–System OK–

9T2 – 8IIMMOBILIZER ANTI–THEFT SYSTEM
DAEWOO V–121 BL4
KEY STATUS ERRORS (MR–140,
HV–240, SIRIUS D4)
The following KEY STATUS messages may be shown on
the scan tool after commanding FIRST KEY CODING and
KEY ADD:
S IGNITION OFF STATUS. This message informs
the technician that the ignition is off during the key
coding process. Turn the ignition ON during key
coding, but do not start the engine.
S KEY IS OCCUPIED. Only five keys may be coded.
If a new key is desired, the previous key codes
must be deleted. Up to five keys may then be au-
thorized.
S ALREADY AUTHORIZED. Key coding is being at-
tempted with a key that is already authorized.
S ERROR NO. A3, A4, A5. There is no communica-
tion between the transponder in the ignition key and
the detection coil. Follow the steps below to diag-
nose the problem:
1) Try a different key. If a different key works, the
problem was in the original key.
2) If trying a different key resulted in the same
error message, replace the detection coil.
S INVALID KEY. The communication between the
immobilizer control unit and the key transponder
has not validated the key. Follow the steps below to
diagnose the problem:
1) Code the key. Refer to ”Key Coding Procedure”
in this section.
2) If the same message is received after key cod-
ing, check the connection of the detection coil.
3) If the detection coil is okay, replace the immo-
bilizer. Refer to ”Immobilizer Control Unit” in
this section.S NO TRANSPONDER DETECTED. The fault may
be in ignition key transponder, the detection coil, or
the Immobilizer. Follow the steps below to diagnose
the problem:
1) Try a different key. If a different key works, the
problem was in the original key.
2) If trying a different key resulted in the same
error message, check the connection of the
detection coil.
3) If the connection of the detection coil is okay,
disconnect the detection coil and use an ohm-
meter to check for an open detection coil.
4) If the detection coil was not open, replace the
immobilizer control unit. Refer to ”Immobilizer
Control Unit” in this section.
COMMUNICATION BETWEEN
IMMOBILIZER CONTROL UNIT AND
TEST EQUIPMENT (MR–140, HV–240,
SIRIUS D4)
1. Connect the test equipment as described in the
Scan Tool Equipment Manual.
2. If communication between the scan tool and the
test equipment was unsuccessful, wait 30 seconds
and try again.
3. If communication was not successful on the second
try, turn the ignition OFF and check the wire and
connectors between the immobilizer control unit
terminal 7 and the data link connector (DLC) termi-
nal 7.
4. If the wire and connectors between the DLC and
the immobilizer control unit are okay, replace the
immobilizer control unit. Refer to ”Immobilizer Con-
trol Unit” in this section.

IMMOBILIZER ANTI–THEFT SYSTEM 9T2 – 9
DAEWOO V–121 BL4
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 key coding.
6. Use the scan tool command.
7. Verify that the key coding was successful by start-
ing the engine with each of the authorized keys.
ID CODE REPROGRAMMING
Reprogram the identification (ID) code in the following si-
tuations:
S An immobilizer control unit has been replaced.
S 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.
TRANSPONDER
Each valid ignition key has an internal transponder which
is a read /write transponder.
The transponder contains an implementation of a crypto–
algorithm with 96 bits of user configurable secret–key con-
tained in EEPROM and transmits data to the ICU by mod-
ulating the amplitude of the electromagnetic field, and
receives data and commands in a similar way.
IMMOBILIZER CONTROL UNIT
Removal Procedure
1. Remove the imstrument panel lower cover.

9T2 – 10IIMMOBILIZER ANTI–THEFT SYSTEM
DAEWOO V–121 BL4
2. Disconnect the electrical connector from the immo-
bilizer control unit.
3. Remove the immobilizer control unit.
Installation Procedure
1. Install the immobilizer control unit.
2. Connect the electrical connector to the immobilizer
control unit.
3. Install the instrument panel lower cover Important:
After replacing the immobilizer, the keys must be
re–authorized using the key coding procedure. Re-
fer to ”Key Coding Procedure” in this section.