Pinpoint Test A: The Speed Control Is Inoperative
WARNING: This page is about a different car, the 2005 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
- A1 RETRIEVE THE RECORDED POWERTRAIN CONTROL MODULE (PCM) DTCs FROM BOTH THE CONTINUOUS AND ON-DEMAND SELF-TESTS
- Check for recorded PCM DTCs from the continuous and on-demand self-tests.
- Are any DTCs recorded?
- Yes : REFER to the POWERTRAIN CONTROL MODULE (PCM) DIAGNOSTIC TROUBLE CODE (DTC) INDEX for correct diagnosis.
- No : GO to A2.
- A2 CHECK THE SPEED CONTROL SWITCH
- Key in OFF position.
- Disconnect: PCM C175b.
- Measure the resistance between the PCM C175b pin 19, circuit 151 (LB/BK), harness side and the PCM C175b pin 30, circuit 848 (DG/OG), harness side while pressing the speed control buttons as follows:SPEED CONTROL SWITCH RESISTANCE VALUE
Speed Control Switch Resistance Value OFF Less than 5 ohms SET/ACCEL 276 - 324 ohms COAST 552 - 648 ohms RESUME 1,021 - 1,199 ohms ON 1,941 - 2,278 ohms No switch pressed 3,965 - 4,655 ohms - Are the speed control switch resistance values OK?
- Yes : GO to A3.
- No : INSTALL a new speed control switch. REFER to SPEED CONTROL SWITCH . TEST the system for normal operation.
- A3 CHECK THE DIGITAL TRANSMISSION RANGE (TR) SENSOR
- Connect: PCM C175b.
- Apply the parking brake.
- Key in ON position.
- Enter the following diagnostic mode on the diagnostic tool: PCM Digital Transmission Range (TR) Sensor PID.
- Monitor the digital TR sensor PID.
- Select DRIVE.
- Does the PID value agree with the transmission range selector lever position?
- Yes : GO to A4.
- No : Refer to AUTOMATIC TRANSAXLE/TRANSMISSION to continue diagnosis of the digital TR sensor.
- A4 CHECK THE DIGITAL TR SENSOR FOR CORRECT ALIGNMENT
- Check the digital TR sensor alignment. Refer to AUTOMATIC TRANSAXLE/TRANSMISSION .
- Is the digital TR sensor aligned correctly?
- Yes : GO to A5.
- No : ADJUST the digital TR sensor. Refer to AUTOMATIC TRANSAXLE/TRANSMISSION . TEST the system for normal operation.
- A5 CHECK STOPLAMP SWITCH INPUT TO THE LIGHTING CONTROL MODULE (LCM) AND THE ANTI-LOCK BRAKE SYSTEM (ABS) MODULE
- Enter the following diagnostic mode on the diagnostic tool: LCM Stoplamp Switch PID.
- Monitor the LCM stoplamp switch PID while applying and releasing the brake pedal.
- Enter the following diagnostic mode on the diagnostic tool: ABS Module Stoplamp Switch PID.
- Monitor the ABS module stoplamp switch PID while applying and releasing the brake pedal.
- Do the PIDs agree with the stoplamp switch position?
- Yes : GO to A6.
- No : GO to PINPOINT TEST B to continue diagnosis of the stoplamp switch.
- A6 CHECK THE VEHICLE SPEED NOTE: This step may require an assistant.
- Enter the following diagnostic mode on the diagnostic tool: Anti-lock Brake System (ABS) Wheel Speed PID.
- Monitor and record the ABS module wheel speed PID while driving the vehicle at 48 km/h (30 mph) as indicated on the speedometer.
- Enter the following diagnostic mode on the diagnostic tool: PCM Vehicle Speed PID.
- Monitor and record the PCM vehicle speed PID while driving the vehicle at 48 km/h (30 mph).
- Does the speed indicated by the ABS module wheel speed PID match the PCM vehicle speed PID?
- Yes : GO to A7.
- No : REFER to INTRODUCTION - GASOLINE to diagnose the output shaft sensor (OSS) signal.
- A7 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 . CLEAR the DTCs. REPEAT the self-test.
- No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.