DIAGNOSTIC TROUBLE CODE (DTC) - P1629 IMMOBILIZER WRONG COMPUTATION

 

Know your Circuit

  • The key is tested by immobilizer anti-theft system as soon as the ignition switch is turned ON.
  • As the immobilizer control unit or integrated anti-theft control unit reads the key code, the engine can start run with any key that will turn the lock cylinder.
  • The key codes is read and cross -checked with key codes existing in the memory of the immobilizer control unit.
  • The immobilizer control unit sends a serial data release message to the Engine Control Module (ECM) if a valid key is identified.
  •  The release message has an identification (ID) code which ascertains that neither the immobilizer control unit nor the ECM has been substituted to defeat the system.
  •  On receiving an invalid release message, the ECM performs the following action:

        1. Paralyze the fuel injector circuit.

        2.  Paralyze the fuel pump circuit.

    3.  Paralyze the ignition coil.

       4.  A Diagnostic Trouble Code (DTC) will automatically be  set if there is  a detect communication link failure between the ECM and immobilizer control unit.

Pre-requisites for setting the DTC

  DTC will be set if:

·   Ignition switch is turned to ON.

·   Immobilizer option is auto detected.

·   ECM release time window (1.5 or 2 seconds) has expired.

·   Vehicle Speed Sensor (VSS) signal is < 512 km/h.

What happens when DTC sets?

When will DTC clear?

1) The Malfunction Indicator Lamp (MIL) will not illuminate

1) A history DTC will clear after 40 consecutive warm-up cycles without a fault.

 

2) The ECM will store conditions which were present when the DTC was set as Failure Records data only.

 

2) DTC(s) can be cleared by using the scan tool.

 

3) This information will not be stored in the Freeze Frame data.

 

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SUMMARY OF STEPS TO BE FOLLOWED

DTC P1629 - Immobilizer Wrong Computation

 

Step

Process

R    E    S

U     L    T

1

Carry out an EOBD System Check.

Work Done?

IF YES

THEN

 

 

 

Follow Step 2

IF NO

THEN

 Go to "On-Board Diagnostic System Check"

2

  1. Turn the ignition switch OFF.
  2. Connect a scan tool to the Data Link Connector (DLC).
  3.  Now turn the ignition ON.
  4. Select IMMOBILIZER DIAGNOSIS STATUS from the scan tool menu.

Is the communication established between the scan tool and the immobilizer control unit?

IF YES

 THEN

 Follow Step 3

IF NO

 THEN

Go to Section 9T, Immobilizer Anti-Theft System

3

  1. Turn the ignition OFF.
  2. Remove the Immobilizer Control Unit and Engine Control Module (ECM) connectors.
  3. Measure the resistance between terminal 7 of immobilizer control unit and terminal 56 of the ECM

Note: the value at this point is 0 ?

Do you see that the resistance is within the specified value?

 

 

 

 

IF YES

THEN

 Follow Step 5

 

 

 

 

IF NO

THEN

Follow Step 4

4

Correct the open circuit between terminal 7 of immobilizer control unit and terminal 56 of the ECM.

Work Done?

IF YES

 THEN

 Follow Step 8

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5

Inspect the terminals in immobilizer control unit and the ECM for damages and repair as necessary.

Work over?

IF YES

THEN

 Follow Step 8

IF NO

THEN

 Follow Step 6

6

Change the immobilizer control unit.

Is the change made?

IF YES

THEN

Step 8

IF NO

THEN

 Follow Step 7

7

  1. Turn the ignition OFF.
  2. Change the ECM.

Is the task over?

IF YES

 THEN

 Follow Step 8

-

8

  1. Clear the Diagnostic Trouble Codes (DTCs) by taking a scan tool.
  2. Start the engine and idle at normal operating temperature.
  3. Run the vehicle within the Conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has run and passed?

IF YES

 THEN

 Follow Step 9

IF NO

THEN

 Follow Step 2

9

Check if any additional DTCs are set.

Are there any undiagnosed DTCs shown?

IF YES

THEN

Go to Applicable DTC Table

The system of your vehicle is fine.