Ford Mustang (1999-2004) Service Manual: Pinpoint Tests

CAUTION: Before removing and installing the GEM or its connectors, disconnect the battery. Failure to follow this caution will result in the GEM storing many erroneous DTCs and may result in the GEM exhibiting erratic operation after installation.

CAUTION: Be careful when probing the central junction box (CJB), battery junction box (BJB), or any connectors. Damage will result to the connector receptacle if the probe being used is too large.

CAUTION: Electronic modules are sensitive to static electrical charges. If exposed to these charges, damage may result.

NOTE: If continuous DTCs are recorded and the symptom is not present when carrying out the pinpoint tests, an intermittent concern may be the cause. Always check for loose connections and corroded terminals.

NOTE: Complete the entire pinpoint test related to the symptom before installing a new GEM.

PINPOINT TEST A: NO COMMUNICATION WITH THE GENERIC ELECTRONIC MODULE

Test Step Result / Action to Take
CAUTION: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
A1 GENERIC ELECTRONIC MODULE (GEM) POWER SUPPLY Yes

GO to A2 .

No

REPAIR the circuit(s) in question. TEST the system for normal operation.
  • Key in OFF position.
  • Disconnect: Generic Electronic Module (GEM) C201a.
  • Disconnect: GEM C201b.
  • Key in ON position.
  • Using the following table, measure the voltage between the GEM, harness side and ground.

  • Are the voltages greater than 10 volts?
A2 CHECK THE GEM GROUND CIRCUIT 397 (BK/WH) FOR OPEN Yes

GO to A3 .

No

REPAIR the circuit(s) in question. TEST the system for normal operation.
  • Key in OFF position.
  • Measure the reistance between the GEM C201b pin 2, circuit 397 (BK/WH), harness side and ground.

  • Is the resistance less than 5 ohms?
A3 CHECK CIRCUIT 397 (BK/WH) FOR SHORT TO POWER Yes

REPAIR the circuit. TEST the system for normal operation.

No

REFER to Section
  • Measure the voltage between GEM C201b pin 2, circuit 397 (BK/WH), harness side and ground.

  • Is any voltage present?

PINPOINT TEST B: THE COURTESY LAMPS ARE INOPERATIVE

Test Step Result / Action to Take
B1 CHECK IGNITION STATES Yes

GO to B2 .

No

For key-in-ignition concerns, REFER to Section
  • Monitor the GEM PIDS IGN_KEY, IGN_A, IGN_S, and IGN_R while cycling the ignition switch through the OFF, ACC, RUN, START and key out positions.
  • Do the PID values agree with the ignition switch positions?
B2 CHECK THE DOOR AJAR INPUT TO THE GEM Yes

GO to B3 .

No

REFER to Section
  • Monitor the GEM PID D_DOOR, and P_DOOR, while opening and closing the driver and passenger doors.
  • Do the GEM PIDS D_DOOR and P_DOOR agree with the driver and passenger door positions?
B3 CHECK THE DOME LAMP SWITCH STATUS INPUT TO THE GEM - MONITOR THE GEM PID DOMESW Yes

GO to B4 .

No

GO to B13 .
  • Monitor the GEM PID DOMESW, while activating, and deactivating the dome lamp switch.
  • Does the GEM PID DOMESW agree with the dome lamp switch position?
B4 CHECK THE LUGGAGE COMPARTMENT LID AJAR INPUT TO THE GEM - MONITOR THE GEM PID DECKLID Yes

GO to B5 .

No

GO to B16
  • Monitor the GEM PID DECKLID, while opening and closing the luggage compartment lid.
  • Does the GEM PID DECKLID agree with the dome switch position?
B5 CHECK THE COURTESY LAMP CIRCUITS Yes

GO to B12 .

No

GO to B6 .
  • Close the luggage compartment lid and all doors are closed.
  • Turn the dome and map lamp switches to the off position.
  • Are the courtesy lamps illuminated?
B6 CHECK THE GEM CONTROL OF THE COURTESY LAMPS Yes

INSTALL a new GEM. For additional information, REFER to Section. REPEAT the self-test.

CLEAR the DTCs.

No

GO to B7 .
  • Trigger the GEM active command COURTESYL ON and then OFF.
  • Do the courtesy lamps illuminate when the GEM active command COURTESYL ON is triggered, and go out when the GEM active command COURTESYL OFF is triggered?
B7 CHECK THE GEM FOR AN INTERNAL FAULT Yes

GO to B8 .

No

INSTALL a new GEM. For additional information, REFER to Section. REPEAT the self-test.

CLEAR the DTCs
  • Trigger the GEM active command COURTESYL ON, then OFF.
  • Can an audible click be heard coming from the GEM, while triggering the active command COURTESYL ON?
B8 CHECK CIRCUIT 1034 (BK/WH) FOR VOLTAGE Yes

GO to B11 .

No

GO to B9 .
  • Disconnect the dome lamp C929 (coupe) or map lamp C978 (convertible)
  • Trigger the GEM active command COURTESYL ON.
  • Measure the voltage between dome/map lamp C929 (coupe) Pin 3 or map lamp C978 (convertible) Pin 4, Circuit 1034 (BK/WH), harness side and ground.

  • Is the voltage greater than 10 volts?
B9 CHECK CIRCUIT 1006 (DG/WH) FOR OPEN Yes

GO to B10 .

No

REPAIR the circuit.

REPEAT the self-test.

CLEAR the DTCs.
NOTE: Verify battery voltage at CJB Fuse 7 (20A) before carrying out this test.
  • Disconnect: GEM C201a.
  • Measure the voltage between GEM C201a Pin 1, Circuit 1006 (DG/WH), harness side and ground.

  • Is the voltage greater than 10 volts?
B10 CHECK CIRCUIT 1034 (BK/WH) FOR OPEN Yes

INSTALL a new GEM. For additional information, REFER to Section. REPEAT the self-test.

CLEAR the DTCs.

No

REPAIR the circuit.

REPEAT the self-test.

CLEAR the DTCs.
  • Disconnect: GEM C201c.
  • Measure the resistance between GEM C201c Pin 3, Circuit 1034 (BK/WH), harness side and dome/map lamp C929 (coupe) Pin 3 or map lamp C978 (convertible) Pin 4, Circuit 1034 (BK/WH), harness side.

  • Is the resistance less than 5 ohms?
B11 CHECK CIRCUIT 1205 (BK) FOR OPEN Yes

INSTALL a new dome/map lamp assembly. For additional information, REFER to Lamp Assembly- Map/Dome .

No

REPAIR the circuit.

REPEAT the self-test.

CLEAR the DTCs.
  • Measure the resistance between dome/map lamp C929 (coupe) Pin 2 or map lamp C978 (convertible) Pin 1, Circuit 1205 (BK), harness side and ground.

  • Is the resistance less than 5 ohms?
B12 CHECK CIRCUIT 1034 (BK/WH) FOR SHORT TO BATTERY Yes

REPAIR the circuit.

REPEAT the self-test.

CLEAR the DTCs.

No

INSTALL a new GEM. For additional information, REFER to Section. REPEAT the self-test.

CLEAR the DTCs.
  • Measure the voltage between GEM C201c Pin 3, Circuit 1034 (BK/WH), harness side and ground.

  • Is the voltage greater than 10 volts?
B13 CHECK THE COURTESY LAMP OPERATION - MONITOR THE GEM PID DOMESW Yes

GO to B15 .

No

GO to B14 .
  • Monitor the GEM PID DOMESW, while moving the interior lamp switch from the OFF to the ON position.
  • Does the GEM PID DOMESW value always indicate ON?
B14 CHECK CIRCUIT 706 (GY) FOR OPEN Yes

INSTALL a new GEM. For additional information, REFER to Section. REPEAT the self-test.

CLEAR the DTCs.

No

REPAIR the circuit.

REPEAT the self-test.

CLEAR the DTCs.
  • Disconnect: GEM C201e.
  • Measure the voltage between GEM C201e Pin 21, Circuit 706 (GY), harness side and ground.

  • Is the voltage greater than 10 volts?
B15 CHECK CIRCUIT 706 (GY) FOR SHORT TO BATTERY Yes

REPAIR the circuit.

REPEAT the self-test.

CLEAR the DTCs.

No

INSTALL a new GEM. For additional information, REFER to Section. REPEAT the self-test.

CLEAR the DTCs.
  • Measure the voltage between GEM C201e Pin 21, Circuit 706 (GY), harness side and ground.

  • Is the voltage greater than 10 volts?
B16 CHECK CIRCUIT 486 (BN/WH) FOR OPEN OR SHORT TO GROUND - MONITOR THE GEM PID DECKLID Yes

GO to B17 .

No

GO to B19 .
  • Monitor the GEM PID DECKLID, while opening and closing the luggage compartment lid.
  • Does the GEM PID DECKLID agree with the luggage compartment lid position?
B17 CHECK LUGGAGE COMPARTMENT SOLENOID FOR SHORT TO GROUND Yes

INSTALL a new luggage compartment solenoid.

For additional information, REFER to Section. REPEAT the selftest.

CLEAR the DTC.

No

GO to B18 .
  • Key in OFF position.
  • Disconnect: Luggage Compartment Solenoid C430.
  • Monitor the GEM PID DECKLID.
  • Does the GEM PID DECKLID indicate closed?
B18 CHECK CIRCUIT 486 (BN/WH) FOR SHORT TO GROUND Yes

INSTALL a new GEM. For additional information, REFER to Section. REPEAT the self-test.

CLEAR the DTCs.

No

REPAIR the circuit.

REPEAT the self-test.

CLEAR the DTCs.
  • Disconnect: GEM C201d.
  • Measure the resistance between GEM C201d Pin 3, Circuit 486 (BN/WH), harness side and ground.

  • Is the resistance greater than 10,000 ohms?
B19 CHECK CIRCUIT 486 (BN/WH) FOR AN OPEN - MONITOR GEM PID DECKLID Yes

GO to B21 .

No

GO to B20 .
  • Disconnect: Luggage Compartment Solenoid C430.
  • Monitor the GEM PID DECKLID.
  • Connect a 10A fused jumper between luggage compartment solenoid C430 Pin 3, Circuit 486 (BN/WH), harness side and ground.

  • Does the GEM PID DECKLID indicate AJAR with the jumper installed?
B20 CHECK CIRCUIT 486 (BN/WH) FOR OPEN Yes

INSTALL a new GEM. For additional information, REFER to Section. REPEAT the self-test.

CLEAR the DTCs.

No

REPAIR the circuit.

REPEAT the self-test. CLEAR the DTCs.
  • Disconnect: GEM C201d.
  • Measure the resistance between GEM C201d Pin 3, Circuit 486 (BN/WH), harness side and luggage compartment solenoid C430 Pin 3, Circuit 486 (BN/WH) harness side.

  • Is the resistance less than 5 ohms?
B21 CHECK GROUND CIRCUIT 1205 (BK) FOR OPEN Yes

INSTALL a new luggage compartment solenoid.

For additional information, REFER to Section. REPEAT the selftest.

CLEAR the DTCs.

No

REPAIR the circuit.

REPEAT the self-test.

CLEAR the DTCs.
  • Measure the resistance between luggage compartment lid switch C430 Pin 1, Circuit 1205 (BK), harness side and ground.

  • Is the resistance less than 5 ohms?

PINPOINT TEST C: THE DEMAND LIGHTING IS INOPERATIVE

Test Step Result / Action to Take
C1 CHECK GEM SUPPLIED POWER TO THE DEMAND LAMPS Yes

GO to C8 .

No

GO to C2 .
  • Turn on both map lamps by depressing the map lamp switches.
  • Turn on both vanity mirror lamps.
  • Open the luggage compartment lid.
  • Do any of the lamps illuminate
C2 CHECK IGNITION STATES Yes

GO to C3 .

No

For key-in-ignition concerns, REFER to Section
  • Monitor the GEM PIDS IGN_KEY, IGN_A, IGN_S, and IGN_R while cycling the ignition switch through the OFF, ACC, RUN, START and key out positions.
  • Do the PID values agree with the ignition switch positions?
C3 CHECK DRIVER AND PASSENGER DOOR AJAR INPUTS TO THE GEM Yes

GO to C4 .

No

REFER to Section
  • Monitor the GEM PIDs D_DOOR and P_DOOR, while opening and closing the driver and passenger doors.
  • Did the GEM PIDs D_DOOR and P_DOOR agree with the driver and passenger door positions?
C4 CHECK INTERIOR LAMP SWITCH INPUT TO THE GEM - MONITOR GEM PID DOMESW Yes

GO to C5 .

No

GO to Pinpoint Test B .
  • Monitor the GEM PID DOMESW, while moving the interior lamp switch from the OFF to the ON position.
  • Does the GEM PID DOMESW values agree with the interior lamp switch positions?
C5 CHECK THE LUGGAGE COMPARTMENT LID AJAR INPUT TO THE GEM - MONITOR THE GEM PID DECKLID Yes

GO to C6 .

No

GO to Pinpoint Test B .
  • Monitor the GEM PID DECKLID, while opening, and closing, the luggage compartment lid.
  • Does the GEM PID DECKLID agree with the luggage compartment lid position?
C6 CHECK CIRCUIT 705 (LG/OG) FOR OPEN Yes

GO to C7 .

No

REPAIR the circuit.

REPEAT the self-test.

CLEAR the DTCs.
  • Turn on both map lamps using the switches in the rear view mirror.
  • Turn on both vanity mirror lamps.
  • Open the luggage compartment lid.
  • Disconnect: GEM C201c.
  • Connect a fused jumper (20A) between GEM C201c Pin 4, Circuit 705 (LG/OG), harness side and battery positive terminal.

  • Do the demand lamps illuminate?
C7 CHECK CIRCUIT 1006 (DG/WH) FOR OPEN Yes

INSTALL a new GEM. For additional information, REFER to Section. REPEAT the self-test.

CLEAR the DTCs.

No

REPAIR the circuit.

REPEAT the self-test.

CLEAR the DTCs.
NOTE: Verify battery voltage at CJB Fuse 7 (20A) before carrying out this test.
  • Disconnect: GEM C201a.
  • Measure the voltage between GEM C201a Pin 1, Circuit 1006 (DG/WH), harness side and ground.

  • Is the voltage greater than 10 volts?
C8 CHECK CIRCUIT 705 (LG/OG) FOR VOLTAGE AT INOPERATIVE DEMAND LAMP Yes

GO to C9 .

No

REPAIR the circuit in question. REPEAT the self-test. CLEAR the DTCs.
  • Key in OFF position.
  • Disconnect inoperative demand lamp, dome/map C929 (coupe), map C907 (convertible), right hand vanity C906, left hand vanity C978, or luggage compartment C4111.
  • Measure the voltage between inoperative demand lamp, Circuit 705 (LG/OG), harness side and ground.

  • Is the voltage greater than 10 volts?
C9 CHECK CIRCUIT 1205 (BK) FOR OPEN AT INOPERATIVE DEMAND LAMP Yes

INSTALL a new demand lamp assembly. REPEAT the self-test. CLEAR the DTCs.

No

REPAIR the circuit in question. REPEAT the self-test. CLEAR the DTCs.
  • Measure the resistance between inoperative demand lamp Circuit 1205 (BK), harness side and ground.

  • Is the resistance less than 5 ohms?

PINPOINT TEST D: THE ILLUMINATED ENTRY IS INOPERATIVE WHEN USING THE REMOTE TRANSMITTER

Test Step Result / Action to Take
D1 CHECK THE REMOTE TRANSMITTER INPUT TO THE GEM Yes

GO to D2 .

No

REFER to Section
  • Remove the ignition key from the ignition.
  • Depress the lock and then the unlock buttons on the remote transmitter.
  • Do the doors lock when the lock button is depressed and unlock when the unlock button is depressed?
D2 CHECK OPERATION OF ILLUMINATED ENTRY WITHOUT REMOTE TRANSMITTER Yes

INSTALL a new GEM. For additional information, REFER to Section.

REPEAT the self-test. CLEAR the DTCs.

No

GO to Pinpoint Test B
  • Open the driver door.
  • Do the courtesy lamps illuminate?

PINPOINT TEST E: THE BATTERY SAVER DOES NOT DEACTIVATE AFTER TIMEOUT

Test Step Result / Action to Take
E1 CHECK THE GEM CONTROL OF THE BATTERY SAVER FUNCTION - TRIGGER THE GEM ACTIVE COMMAND BATT SAVR ON Yes

INSTALL a new GEM.

For additional information, REFER to Section.

REPEAT the self-test.

CLEAR the DTCs.

No

GO to E2 .
  • Trigger the GEM active command BATT SAVR ON and then OFF.
  • Do the courtesy lamps illuminate and turn off when the GEM active command BATT SAVR is triggered ON and OFF?
E2 CHECK CIRCUITS 1034 (BK/WH), AND 705 (LG/OG), FOR SHORT TO BATTERY Yes

REPAIR the circuit in question. REPEAT the self-test. CLEAR the DTCs.

No

INSTALL a new GEM.

For additional information, REFER to Section.

REPEAT the self-test.

CLEAR the DTCs.
  • Disconnect: GEM C201c.
  • Measure the voltage between GEM C292 Pin 3, Circuit 1034 (BK/WH), harness side and ground; and between GEM C292 Pin 4, Circuit 705 (LG/OG), harness side and ground.

  • Is the voltage greater than 10 volts?
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