2010 Cadillac Truck SRX AWD V6-2.8L Turbo Page 1086
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at Q38 throttle body.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohm
between the low reference circuit terminal C and ground.
瀚慖f greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests
normal, replace the K20 engine control module.
3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal E and ground.
瀚慖f less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20
engine control module.
瀚慖f greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the K20 engine control module.
4. Ignition ON, verify that the scan tool Throttle Position Sensor 1 Voltage parameter is less than 0.3 V.
瀚慖f greater than the specified value, test the signal circuit terminal D for a short to voltage. If the circuit tests normal, replace the K20
engine control module.
5. Connect a 3 A fused jumper wire between the 5 V reference circuit terminal E and the throttle position sensor 1 signal circuit terminal D.
Verify the scan tool Throttle Position Sensor 1 Voltage parameter is greater than 4.89 V.
瀚慖f less than the specified value, test the signal circuit for an open/high resistance or for a short to ground. If the circuit tests normal,
replace the K20 engine control module.
6. Verify the scan tool Throttle Position Sensor 2 Voltage parameter is greater than 4.97 V.
瀚慖f less than the specified value, test the signal circuit terminal F for a short to ground. If the circuit tests normal, replace the K20 engine
control module.
Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage.
7. Connect a 3 A fused jumper wire between the throttle position sensor 2 signal circuit terminal F and the low reference circuit terminal C.
Verify the scan tool Throttle Position Sensor 2 Voltage parameter is less than 0.10 V.
瀚慖f greater than the specified value, test the signal circuit for an open/high resistance or for a short to voltage. If the circuit tests normal,
replace the K20 engine control module.
8. If all circuits test normal, replace the Q38 throttle body assembly.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* 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 (LAU) (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 engine control module replacement,
programming, and setup
P0128
DTC P0128 (LAU)
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 P0128
- Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature
