2010 Cadillac CTS Sedan AWD V6-3.0L Page 1541
Note: If DTC P0218 is set, diagnose that DTC first.
1. Perform the Transmission Fluid Level and Condition Check (See: Transmission and Drivetrain/Automatic Transmission/Transaxle/Testing
and Inspection/Initial Inspection and Diagnostic Overview/Transmission Fluid Level and Condition Check) to verify correct fluid level and
condition.
2. Operate the vehicle to normal engine temperature is reached. Verify with a scan tool the engine coolant temperature (ECT) sensor parameter
is less than 125掳C (257掳F).
瀚慖f greater than the specified value, refer to Symptoms - Engine Cooling (See: Engine, Cooling and Exhaust/Cooling System/Testing and
Inspection/Symptom Related Diagnostic Procedures/Symptoms - Engine Cooling).
3. Operate the vehicle till normal engine temperature is reached. Verify with a scan tool, the TCM temperature parameter is less than 142掳C
(287掳F).
瀚慖f greater than the specified value, inspect the transmission fluid lines for being misrouted, kinked, or damage.
4. If all items test normal, replace the Q8 control solenoid valve assembly.
5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the
conditions that you observed from the Freeze Frame/Failure Records data.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Control solenoid valve assembly replacement. Refer to Control Module References (See: Testing and Inspection/Programming and
Relearning) for replacement, setup, and programming.
* Perform the Service Fast Learn Adapts (See: Transmission and Drivetrain/Automatic Transmission/Transaxle/Testing and
Inspection/Programming and Relearning/Service Fast Learn Adapts) following all transmission related repairs.
P0638
DTC P0638, P2100, P2101, or P2119 (Without LF1)
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 Descriptors
DTC P0638
- Throttle Actuator Control (TAC) Command Performance
DTC P2100
- Throttle Actuator Control (TAC) Motor Control Circuit
DTC P2101
- Throttle Actuator Position Performance
DTC P2119
- Throttle Closed Position Performance
Diagnostic Fault Information
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 sensors 1 and
2 to determine the actual throttle valve position.
