Pinpoint Test A: The Speed Control Is Inoperative
Speed Control
Pinpoint Tests
Pinpoint Test A: The Speed Control Is Inoperative
Refer to Wiring Diagram Set 31, Speed Control for schematic and connector information. Diagrams By Number
Normal Operation
The PCM sends a signal through circuit VES10 (WH) to the speed control switch, which passes through the clockspring. The return signal is sent to the PCM through circuit RES08 (GN/BN) and the clockspring. When the brake pedal is applied, the stoplamp switch sends a voltage signal to the PCM on circuit CCB08 (VT/WH) to deactivate the speed control if engaged.
The speed control deactivator switch, which is integral to the stoplamp switch, interrupts circuit CES09 (VT/OG) removing the voltage signal to the PCM when the brake pedal is applied. This is a redundant signal to the PCM.
The ABS module monitors brake pressure and also receives a voltage signal on circuit CCB08 (VT/WH) from the stoplamp switch . A fault in the ABS module can disable the speed control system.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- PCM not configured for speed control
- Stoplamp switch
- Speed control deactivator switch (integral to the stoplamp switch)
- Speed control switch
- Digital Transmission Range (TR) sensor
- Vehicle speed signal
- PCM
- ABS module
PINPOINT TEST A: THE SPEED CONTROL IS INOPERATIVE
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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A1 VERIFY PCM CONFIGURATION
- Enter the following diagnostic mode on the scan tool: Programmable Parameters.
- Verify that the speed control is enabled in the PCM.
- Is the speed control enabled?
Yes
GO to A2.
No
ENABLE the speed control in the PCM using the scan tool programmable parameters menu. TEST the system for normal operation.
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A2 CHECK FOR ABS DTCs
- Review the recorded DTCs from the ABS self-test.
- Are any DTCs recorded?
Yes
REFER to the Antilock Brakes / Traction Control Systems. REPAIR all ABS module DTCs and RETEST the speed control. Testing and Inspection
No
GO to A3.
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A3 CHECK FOR PCM DTCs
- Review the recorded DTCs from the PCM self-test.
- Are any non-speed control DTCs recorded?
Yes
REFER to Computers and Control Systems Information. REPAIR all PCM DTCs and RETEST the speed control.
No
GO to A4.
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A4 CHECK THE VEHICLE SPEED
- Check for correct operation of the speedometer.
- Does the speedometer operate correctly?
Yes
GO to A5.
No
REFER to Instrument Panel, Gauges and Warning Indicators to continue diagnosis of the speedometer.
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A5 CHECK THE STOPLAMP SWITCH (BOO AND BPA) PID
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: PCM DataLogger.
- Monitor the PCM PIDs BOO (brake pedal top travel) and BPA (brake pedal bottom travel) while applying and releasing the brake pedal as follows:
- Do the PID values agree with the brake pedal positions?
Yes
GO to A6.
No
Go To Pinpoint Test B. Pinpoint Test B: DTC P1572 Or DTC P1703
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A6 MONITOR THE PCM (TR) PID
- Apply the parking brake.
- Enter the following diagnostic mode on the scan tool: PCM DataLogger.
- Monitor the PCM PID (TR) .
- Select DRIVE.
- Does the PID value agree with the transmission range selector lever position?
Yes
GO to A7.
No
REFER to Transmission Control Systems to diagnose the digital TR sensor. Testing and Inspection
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A7 CHECK THE SPEED CONTROL SWITCH
- Enter the following diagnostic mode on the scan tool: PCM DataLogger.
- Press each speed control switch while monitoring the speed control switch PID (SCCS).
- Does the PID value agree with the switch position?
Yes
GO to A8.
No
If only one switch does not display the correct PID value, INSTALL a new speed control switch. REFER to Speed Control Switch Service and Repair. TEST the system for normal operation.
Otherwise, Go To Pinpoint Test C. Pinpoint Test C: The Speed Control Switches Do Not Operate Correctly
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A8 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the PCM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new PCM. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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