Pinpoint Test A: The Speed Control Is Inoperative

WARNING: This page is about a different car, the 2005 Lincoln Navigator and 2005 Ford Expedition. 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 .
- No : GO to A2.

A2 CHECK THE SPEED CONTROL SWITCH

Key in OFF position.
Disconnect: PCM C175b.

Measure the resistance between the PCM C175b-56, circuit 151 (LB/BK), harness side and the PCM C175b-57, circuit 848 (DG/OG), harness side while pressing the speed control buttons as follows:

SPEED CONTROL SWITCH RESISTANCE

Speed Control Switch	Resistance Value
OFF	Less than 5 ohms
CANCEL	114 - 126 ohms
SET-	285-315 ohms
SET +	570 - 630 ohms
RESUME	1,055 - 1,165 ohms
ON	2,004 - 2,216 ohms
No switch pressed	4,094 - 4,526 ohms

Fig 1: Checking Speed Control Switch Resistance

Courtesy of FORD MOTOR CO.

Are the speed control switch resistance values OK?

Yes : GO to A3.
No : INSTALL a new speed control switch. REFER to SPEED CONTROL SWITCH - WITH REMOTE AUDIO/CLIMATE CONTROL or SPEED CONTROL SWITCH - WITHOUT REMOTE AUDIO/CLIMATE CONTROL in this section. 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 scan 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 TRANSMISSION - 6HP26 or AUTOMATIC TRANSMISSION - 4R70E/4R75E 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 TRANSMISSION - 6HP26 or AUTOMATIC TRANSMISSION - 4R70E/4R75E .
- Is the digital TR sensor aligned correctly?
- Yes : GO to A5.
- No : ADJUST the digital TR sensor. REFER to AUTOMATIC TRANSMISSION - 6HP26 or AUTOMATIC TRANSMISSION - 4R70E/4R75E . TEST the system for normal operation.
A5 CHECK THE BRAKE WARNING INDICATOR
- Key in ON position.
- While observing the brake warning indicator, apply and release the parking brake.
- Does the brake warning indicator operate correctly?
- Yes : GO to A6.
- No : REFER to INSTRUMENT CLUSTER to continue diagnosis of the brake warning indicator.
A6 CHECK THE VEHICLE SPEED
NOTE: This step may require an assistant.
- Enter the following diagnostic mode on the scan 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 scan 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 : See INTRODUCTION - GASOLINE article 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.