2010 Cadillac CTS Sedan AWD V6-3.0L Page 1766
6. Ignition OFF, measure the voltage using the DMM Min/Max Recording Mode function on each circuit listed below as the ignition is turned
ON. The Max voltage should be within 1 V of B+.
* TAC Motor Control Closed circuit terminal A
* TAC Motor Control Open circuit terminal B
瀚慖f not within the specified range, test the circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
7. If all circuits and connections test normal, replace the throttle body assembly.
Repair Instructions
* Throttle Body Assembly Replacement (LF1) (See: Powertrain Management/Fuel Delivery and Air Induction/Throttle Body/Service and
Repair/Removal and Replacement)Throttle Body Assembly Replacement (LLT) (See: Powertrain Management/Fuel Delivery and Air
Induction/Throttle Body/Service and Repair/Removal and Replacement)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for ECM replacement, setup, and programming
Repair Verification
1. Install any components that have been removed or replaced during diagnosis.
2. Perform any adjustments, programming or setup procedures that are required when a component is removed or replaced.
3. Clear the DTCs with a scan tool.
4. Turn OFF the ignition for 60 seconds.
Note: If the Throttle Sweep Test is not available on the scan tool, use the accelerator to perform the test. Refer to Diagnostic Aids for further
details.
5. Perform the Throttle Sweep Test while observing the TAC Motor parameter with a scan tool. The TAC Motor parameter should display
Enabled while the Throttle Sweep Test is in progress.
6. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in
order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the Diagnostic Trouble Code (DTC) List -
Vehicle (See: Diagnostic Trouble Code Descriptions/Diagnostic Trouble Code (DTC) List - Vehicle) and perform the appropriate diagnostic
procedure.
P1551
DTC P1551
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC P1551
- Throttle Valve Rest Position Not Reached During Learn
Circuit/System Description
The engine control module (ECM) controls the throttle valve by applying a varying voltage to the control circuits of the throttle actuator control
(TAC) motor. The ECM monitors the duty cycle that is required to actuate the throttle valve. The ECM monitors the throttle position (TP) sensors 1
and 2 to determine the actual throttle valve position.
Conditions for Running the DTC
* The vehicle speed is 0 km/h (0 mph).
* The engine speed is 0 RPM.
* The engine coolant temperature (ECT) is between 5-100掳C (41-212掳F).
* The intake air temperature (IAT) is between 5-144掳C (41-291掳F).
* The ignition voltage is greater than 10 volts.
* The accelerator pedal position (APP) is less than 15 percent.
* DTC P1551 runs when the conditions above have been met for greater than 5 seconds.
