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Home >> Mercury >> 2008 >> Milan Base, 3.0 1, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1727 (Anti-Theft System - Perimeter) >> Diagnostic Tests >> Anti-Theft - Perimeter >> Pinpoint Tests >> Pinpoint Test A: The Alarm System Does Not Operate Correctly

Pinpoint Test A: The Alarm System Does Not Operate Correctly

WARNING: This page is about a different car, the 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Luggage Compartment for schematic and connector information.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Remote Keyless Entry and Alarm for schematic and connector information.

Normal Operation 

The lighting control module (LCM) receives an unlock signal from the door disarm switch through circuit 25 (DG/VT) by using the ground through circuit 57 (BK), and turns off the anti-theft perimeter alarm. The LCM monitors the key-in-ignition switch and does not allow the perimeter anti-theft feature to arm until after the key is removed from the ignition lock cylinder, all doors, hood, luggage compartment lid are closed, and 20 seconds have elapsed after locking the vehicle. After all of these criteria have been met, the anti-theft feature will arm.

The LCM monitors the hood switch on circuit 1304 (VT/OG) to prevent the alarm from being armed while the hood is open. If the LCM does not receive a ground signal on circuit 1304 (VT/OG), the LCM will not arm the alarm. The hood switch is grounded by circuit 57 (BK). After the perimeter alarm is armed, the LCM monitors the hood switch on circuit 1304 (VT/OG) to determine if an unauthorized entry to the vehicle has occurred. If the hood switch opens circuit 1304 (VT/OG) to ground (with the perimeter alarm armed), the LCM will activate the perimeter alarm.

If not equipped with the liftgate/trunk module (LTM), the trunk pull-down module monitors the luggage compartment lid ajar switch on circuit 486 (BN/WH). The switch status is provided to the LCM by the trunk pull-down module through circuit 700 (WH/VT). If the trunk pull-down module does not receive a ground signal on circuit 486 (BN/WH), the LCM will not arm the alarm. The luggage compartment lid ajar switch is grounded by circuit 57 (BK).

If equipped with the LTM, the LTM monitors the luggage compartment lid ajar switch on circuit 486 (BN/WH). The switch status is provided to the LCM by the LTM through circuit 700 (WH/VT). If the LTM does not receive a ground signal on circuit 486 (BN/WH), the LCM will not arm the alarm. The luggage compartment lid ajar switch is grounded by circuit 57 (BK).

The driver door module (DDM) receives lock/unlock commands from the remote keyless entry (RKE) transmitter and sends a message over the standard corporate protocol (SCP) communication link to the LCM. The LCM then arms/disarms the perimeter alarm system if all arming conditions have been met.

When the alarm is activated, the LCM intermittently grounds the horn relay, causing the horn to sound in regular intervals, and intermittently sends voltage to the turn signals, causing the turn signal lamps to flash in regular intervals.

This pinpoint test is intended to diagnose the following: 

PINPOINT TEST A: THE ALARM SYSTEM DOES NOT OPERATE CORRECTLY 

NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. A1 CHECK THE RECORDED LCM DTCs 
    • Check the recorded results from the LCM self-test.
    • Is DTC B2100 retrieved? 
    1. YES  : Go to  A10.
    2. NO  : If DTC B1520 is retrieved, go to  A5.

      If DTC B2108 is retrieved, go to  A15.

      If no DTCs are retrieved, go to  A2.

  2. A2 CHECK THE RKE TRANSMITTER FUNCTION 
    • Using the RKE transmitter(s), lock and unlock the doors and operate the panic function.
    • Do all the RKE transmitter(s) functions operate correctly, including the parking lamps flash and the horn? 
    1. YES  : Go to  A3.
    2. NO  : REFER to DIAGNOSTIC TESTS article to continue diagnosis.
  3. A3 CHECK THE KEYLESS ENTRY KEYPAD FUNCTION 
    • Lock and unlock the doors using the keyless entry keypad.
    • Do all the doors lock and unlock using the keyless entry keypad? 
    1. YES  : Go to  A4.
    2. NO  : REFER to DIAGNOSTIC TESTS article to continue diagnosis.
  4. A4 VERIFY THAT ALL THE DOORS AND THE LUGGAGE COMPARTMENT LID ARE CLOSED 
    • Key in ON position.
    • Close all the doors and the luggage compartment lid.
    • Are any ajar indicators illuminated? 
    1. YES  : REFER to DIAGNOSTIC TESTS article to diagnose the interior lamps are always on.
    2. NO  : Go to  A5.
  5. A5 CHECK THE HOOD SWITCH CIRCUITRY 
    • Connect the diagnostic tool.
    • Enter the following diagnostic mode on the diagnostic tool: LCM DataLogger
    • While opening and closing the hood, monitor the LCM HOOD_SW PID.
    • Does the PID indicate OPEN with the hood open and CLOSED with the hood closed? 
    1. YES  : Go to  A10.
    2. NO  : Go to  A6.
  6. A6 CHECK THE HOOD SWITCH INTEGRITY 
    • Key in OFF position.
    • Disconnect: Hood Switch C127
    • Key in ON position.
    • Monitor the LCM HOOD_SW PID.
    • Does the PID indicate OPEN? 
    1. YES  : Go to  A7.
    2. NO  : Go to  A9.
  7. A7 CHECK CIRCUIT 57 (BK) FOR AN OPEN TO THE HOOD SWITCH 
    • Key in OFF position.
      • Fig 1: Checking Circuit For An Open
      GF0019136Courtesy of FORD MOTOR CO.
    • Measure the resistance between the hood switch C127-2, circuit 57 (BK), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  A8.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  8. A8 CHECK CIRCUIT 1304 (VT/OG) FOR AN OPEN 
    • Disconnect: LCM C2145a
      • Fig 2: Checking Circuit For An Open
      GF0019137Courtesy of FORD MOTOR CO.
    • Measure the resistance between the LCM C2145a-2, circuit 1304 (VT/OG), harness side, and the hood switch C127-1, circuit 1304 (VT/OG), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : INSTALL a new hood switch. CLEAR the DTCs. REPEAT the self-test.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  9. A9 CHECK CIRCUIT 1304 (VT/OG) FOR A SHORT TO GROUND 
    • Key in OFF position.
    • Disconnect: LCM C2145a
      • Fig 3: Checking Hood Switch Circuit
      GF0014672Courtesy of FORD MOTOR CO.
    • Measure the resistance between the LCM C2145a-2, circuit 1304 (VT/OG), harness side and ground.
    • Is the resistance greater than 10,000 ohms? 
    1. YES  : Go to  A18.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  10. A10 CHECK THE DOOR DISARM CIRCUIT 
    • Key in OFF position.
    • Disconnect: LCM C2145b
    • Insert the key in the driver door lock cylinder.
    • With the key in the UNLOCK position, measure the resistance between the LCM C2145b-9, circuit 25 (DG/VT), harness side and ground.
    • With the key in the AT-REST position, measure the resistance between the LCM C2145b-9, circuit 25 (DG/VT), harness side and ground.
    • Is the resistance less than 5 ohms with the key in the UNLOCK position, and greater than 10,000 ohms with the key in the AT-REST position? 
    1. YES  : Go to  A11.
    2. NO  : If the resistance is always greater than 10,000 ohms, go to  A12.

      If not, go to  A13.

  11. A11 CHECK THE DOOR ARM CIRCUIT 
    • Turn and hold the driver door lock cylinder in the LOCK position, then to the AT-REST position.
    • With the key in the UNLOCK position, measure the resistance between the LCM C2145b-10, circuit 24 (DB/OG), harness side and ground.
    • With the key in the AT-REST position, measure the resistance between the LCM C2145b-10, circuit 24 (DB/OG), harness side and ground.
    • Is the resistance less than 5 ohms with the key in the UNLOCK position, and greater than 10,000 ohms with the key in the AT-REST position? 
    1. YES  : Go to  A15.
    2. NO  : If the resistance is always greater than 10,000 ohms, go to  A12.

      If not, go to  A14.

  12. A12 CHECK CIRCUIT 57 (BK) FOR AN OPEN 
    • Disconnect: Door Disarm Switch C509
      • Fig 4: Checking Circuit For An Open
      GF0014673Courtesy of FORD MOTOR CO.
    • Measure the resistance between the door disarm switch C509-3, circuit 57 (BK), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : INSTALL a new door disarm switch. REFER to Door Disarm Switch . TEST the system for normal operation.
    2. NO  : REPAIR the circuit. TEST the system for normal operation.
  13. A13 CHECK CIRCUIT 25 (DG/VT) FOR AN OPEN OR SHORT TO GROUND 
    • Disconnect: Door Disarm Switch C509
      • Fig 5: Checking Circuit For An Open Or Short To Ground
      GF0019141Courtesy of FORD MOTOR CO.
    • Measure the resistance between the LCM C2145b-9, circuit 25 (DG/VT), harness side, and the door disarm switch C509-2, circuit 25 (DG/VT), harness side; and between the LCM C2145b-9, circuit 25 (DG/VT), harness side and ground.
    • Is the resistance less than 5 ohms between the LCM and the door disarm switch, and greater than 10,000 ohms between the LCM and ground? 
    1. YES  : INSTALL a new door disarm switch. REFER to Door Disarm Switch . CLEAR the DTCs. REPEAT the self-test.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  14. A14 CHECK CIRCUIT 24 (DB/OG) FOR AN OPEN OR SHORT TO GROUND 
    • Disconnect: Door Disarm Switch C509
      • Fig 6: Checking Circuit For An Open Or Short To Ground
      GF0019140Courtesy of FORD MOTOR CO.
    • Measure the resistance between the LCM C2145b-10, circuit 24 (DB/OG), harness side, and the door disarm switch C509-1, circuit 24 (DB/OG), harness side; and between the LCM C2145b-10, circuit 24 (DB/OG), harness side and ground.
    • Is the resistance less than 5 ohms between the LCM and the door disarm switch, and greater than 10,000 ohms between the LCM and ground? 
    1. YES  : INSTALL a new door disarm switch. REFER to Door Disarm Switch . CLEAR the DTCs. REPEAT the self-test.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  15. A15 CHECK CIRCUIT 1350 (WH/PK) FOR AN OPEN OR SHORT TO GROUND 
    • Key in OFF position.
    • Disconnect: LCM C2145b
    • Disconnect: Luggage Compartment Lid Disarm Switch C4225
      • Fig 7: Checking Circuit For An Open Or Short To Ground
      GF0019143Courtesy of FORD MOTOR CO.
    • Measure the resistance between the LCM C2145b-12, circuit 1350 (WH/PK), harness side, and the luggage compartment lid disarm switch C4225-2, circuit 1350 (WH/PK), harness side; and between the LCM C2145b-12, circuit 1350 (WH/PK), harness side and ground.
    • Is the resistance less than 5 ohms between the LCM and the luggage compartment lid disarm switch, and greater than 10,000 ohms between the LCM and ground? 
    1. YES  : Go to  A16.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  16. A16 CHECK CIRCUIT 57 (BK) FOR AN OPEN 
      Fig 8: Checking Circuit For An Open
      GF0014676Courtesy of FORD MOTOR CO.
    • Measure the resistance between the luggage compartment lid disarm switch C4225-1, circuit 57 (BK), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  A17.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  17. A17 CHECK THE LUGGAGE COMPARTMENT LID DISARM SWITCH 
      Fig 9: Measuring Resistance
      GF0047693Courtesy of FORD MOTOR CO.
    • Measure the resistance between the luggage compartment lid disarm switch C4225 pin 1 and pin 2, component side, while turning the luggage compartment lid key cylinder to the UNLOCK and the AT-REST positions.
    • Is the resistance less than 5 ohms with the switch turned to the UNLOCK position, and greater than 10,000 ohms when in the AT-REST position? 
    1. YES  : Go to  A18.
    2. NO  : INSTALL a new luggage compartment lid disarm switch. REFER to Luggage Compartment Lid Lock Cylinder in REMOVAL AND INSTALLATION article. CLEAR the DTCs. REPEAT the self-test.
  18. A18 CHECK FOR CORRECT LCM OPERATION 
    • Disconnect all the LCM connectors.
    • Check for:
      • corrosion
      • damaged pins
      • pushed-out pins
    • Connect all the LCM connectors and make sure they seat correctly.
    • Operate the system and verify the concern is still present.
    • Is the concern still present? 
    1. YES  : INSTALL a new LCM. REFER to REMOVAL AND INSTALLATION article. REPEAT the self-test. TEST the system for normal operation.
    2. NO  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.
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