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HOMESERVICE MANUALSMERCURY1999TRACER LS, 4D SEDAN, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)EXTERNAL PAGESDIFFERENT CARSECTION 130 (CRUISE CONTROL SYSTEM -- F250-F550 SUPER DUTY)DIAGNOSIS AND TESTINGSPEED CONTROLPINPOINT TESTSPINPOINT TEST C: DTC P0579 OR DTC P0581 - SPEED CONTROL SWITCH CIRCUIT FAILURE

1999 Mercury Tracer LS, 4D Sedan, Standard

Pinpoint Test C: DTC P0579 Or DTC P0581 - Speed Control Switch Circuit Failure

1999 Mercury Tracer LS, 4D Sedan, StandardSECTION Pinpoint Test C: DTC P0579 Or DTC P0581 - Speed Control Switch Circuit Failure

WARNING: This page is about a different car, the 2005 Ford Pickup, 2005 Ford F550 Super Duty, 2005 Ford F450 Super Duty, and 2005 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

C1 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR A SHORT TO VOLTAGE
- Key in ON position.
- Turn the parking lamps on.
- Measure the voltage between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, circuit 133 (BK), harness side and ground.
  
  Fig 1: Measuring Voltage Between PCM Connector And Ground
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
- Yes : TURN the parking lamps off. GO to C2.
- No : TURN the parking lamps off. GO to C4.
C2 CHECK CIRCUITS 151 (LB/BK) AND 133 (BK) FOR A SHORT TO VOLTAGE
- Key in OFF position.
- Disconnect: Clockspring C218a.
- Key in ON position.
- Turn the parking lamps on.
- Measure the voltage between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, circuit 133 (BK), harness side and ground.
  
  Fig 2: Measuring Voltage Between PCM Connector And Ground
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
- Yes : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
- No : TURN the parking lamps off. GO to C3.
C3 CHECK THE CLOCKSPRING FOR A SHORT TO VOLTAGE
- Key in OFF position.
- Connect: Clockspring C218a.
- Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM .
- Connect the restraint system diagnostic tool (418-F403) to the upper clockspring air bag connector.
- Disconnect: Upper Clockspring.
- Connect the battery.
- Key in ON position.
- Turn the parking lamps on.
- Measure the voltage between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, circuit 848 (DG/OG), harness side and ground.
  
  Fig 3: Measuring Voltage Between PCM Connector And Ground
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
- Yes : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . DISCONNECT the battery. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.
- No : INSTALL a new speed control switch(es) harness. REFER to SPEED CONTROL SWITCH .. DISCONNECT the battery. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.
C4 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR A SHORT TO GROUND
- Key in OFF position.
- Measure the resistance between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, circuit 133 (BK), harness side and ground.
  
  Fig 4: Measuring Resistance Between PCM Connector And Ground
  Courtesy of FORD MOTOR CO.
- Are the resistances greater than 10,000 ohms?
- Yes : GO to C7.
- No : GO to C5.
C5 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND
- Remove the driver air bag module. Refer to SUPPLEMENTAL RESTRAINT SYSTEM . Disconnect: Upper Clockspring.
- Measure the resistance between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, circuit 133 (BK), harness side and ground.
  
  Fig 5: Measuring Resistance Between PCM Connector And Ground
  Courtesy of FORD MOTOR CO.
- Are the resistances greater than 10,000 ohms?
- Yes : INSTALL a new speed control switch(es) harness. REFER to SPEED CONTROL SWITCH .. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.
- No : GO to C6.
C6 CHECK CIRCUITS 151 (LB/BK) AND 133 (BK) FOR A SHORT TO GROUND
- Disconnect: Clockspring C218a.
- Measure the resistance between the PCM C175b-19, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-30, circuit 133 (BK), harness side and ground.
  
  Fig 6: Measuring Resistance Between PCM Connector And Ground
  Courtesy of FORD MOTOR CO.
- Are the resistances greater than 10,000 ohms?
- Yes : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.
- No : REPAIR the circuit in question. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.
C7 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR AN OPEN
- Measure the resistance between the PCM C175b-19, circuit 151 (LB/BK), harness side and the PCM C175b-30, circuit 133 (BK), harness side.
  
  Fig 7: Checking The Speed Control Switch Circuitry For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance between 4,100 and 4,550 ohms?
- Yes : GO to C11.
- No : GO to C8.
C8 CHECK CIRCUITS 151 (LB/BK) AND 133 (BK) FOR AN OPEN
- Disconnect: Clockspring C218a.
- Measure the resistance between the PCM C175b-19, circuit 151 (LB/BK), harness side and the clockspring C218a-7, circuit 151 (LB/BK), harness side; and between the PCM C175b-30, circuit 133 (BK), harness side and the clockspring C218a-2, circuit 133 (BK), harness side.
  
  Fig 8: Checking Circuits 151 (LB/BK) And 133 (BK) For An Open
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
- Yes : If not equipped with steering wheel audio controls, GO to C9.
  If equipped with steering wheel audio controls, GO to C10.
- No : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
C9 CHECK THE CLOCKSPRING
- Remove the driver air bag. Refer to SUPPLEMENTAL RESTRAINT SYSTEM .
- Disconnect: Upper Clockspring.
- Measure the resistance between the clockspring C218a-7, component side and the upper clockspring connector pin 1, component side; and between the clockspring C218a-2, component side and the upper clockspring connector pin 2, component side.
  
  Fig 9: Checking Clockspring
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
- Yes : INSTALL a new speed control switch(es) harness. REFER to SPEED CONTROL SWITCH .. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.
- No : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.
C10 CHECK THE CLOCKSPRING FOR AN OPEN
- Remove the driver air bag. Refer to SUPPLEMENTAL RESTRAINT SYSTEM .
- Disconnect: Upper Clockspring.
- Measure the resistance between the clockspring C218a-7, component side and the upper clockspring connector pin 1, component side; and between the clockspring C218a-2, component side and the upper clockspring connector pin 3, component side.
  
  Fig 10: Checking Clockspring For An Open
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
- Yes : INSTALL a new speed control switch(es) harness. REFER to SPEED CONTROL SWITCH .. INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.
- No : INSTALL a new clockspring. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . INSTALL the driver air bag module. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.
C11 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Check for:
  - corrosion
  - pushed-out pins
- Connect all the PCM connectors and make sure they are seated correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
- Yes : INSTALL a new PCM. REFER to ELECTRONIC ENGINE CONTROLS - GASOLINE ENGINES . INSTALL the driver air bag. REFER to SUPPLEMENTAL RESTRAINT SYSTEM .
- No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. INSTALL the driver air bag. REFER to SUPPLEMENTAL RESTRAINT SYSTEM . CLEAR the DTCs. REPEAT the self-test.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.