2010 Cadillac CTS Sedan AWD V6-3.6L Page 1785
Note: A small delay occurs before the ECM changes the cooling fan speed.
4. Command the cooling fans in both low and high speed.
瀚慖f the cooling fans do not operate in both speeds, refer to Cooling Fan Inoperative (Single Fan) (See: Engine, Cooling and
Exhaust/Cooling System/Testing and Inspection/Symptom Related Diagnostic Procedures/Cooling Fan Inoperative (Single Fan))Cooling
Fan Inoperative (Dual Fan) (See: Engine, Cooling and Exhaust/Cooling System/Testing and Inspection/Symptom Related Diagnostic
Procedures/Cooling Fan Inoperative (Dual Fan)).
5. Test the thermostat for correct operation. Refer to Thermostat Diagnosis (LP1, LY7) (See: Engine, Cooling and Exhaust/Cooling
System/Testing and Inspection/Symptom Related Diagnostic Procedures/Thermostat Diagnosis)Thermostat Diagnosis (LS2) (See: Engine,
Cooling and Exhaust/Cooling System/Testing and Inspection/Symptom Related Diagnostic Procedures/Thermostat Diagnosis).
6. Test the engine cooling system for overheating. Refer to Engine Overheating (LF1, LLT) (See: Engine, Cooling and Exhaust/Cooling
System/Testing and Inspection/Symptom Related Diagnostic Procedures/Engine Overheating)Engine Overheating (LSA) (See: Engine,
Cooling and Exhaust/Cooling System/Testing and Inspection/Symptom Related Diagnostic Procedures/Engine Overheating).
7. Inspect the water pump and coolant flow for correct operation. Refer to Water Pump Replacement (LF1/LLT) (See: Engine, Cooling and
Exhaust/Cooling System/Water Pump/Service and Repair)Water Pump Replacement (LSA) (See: Engine, Cooling and Exhaust/Cooling
System/Water Pump/Service and Repair).
8. Inspect the engine mechanical for worn/leaking/cracked cylinder heads and engine block. Refer to Coolant in Combustion Chamber (See:
Engine, Cooling and Exhaust/Engine/Testing and Inspection/Symptom Related Diagnostic Procedures/Coolant in Combustion Chamber) and
Coolant in Engine Oil (See: Engine, Cooling and Exhaust/Engine/Testing and Inspection/Symptom Related Diagnostic Procedures/Coolant
in Engine Oil).
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
P1400
DTC P1400 (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) provide an overview of each diagnostic category.
DTC Descriptor
DTC P1400
- Cold Start Emission Reduction Control System
Circuit/System Description
The catalytic converter must be warmed to efficiently reduce the emissions. The cold start strategy is to reduce the amount of time it takes to warm
the catalytic converter. During a cold start, the engine idle speed is elevated and spark timing is retarded to allow the catalyst to warm quickly. This
diagnostic monitors the following to build an exhaust energy model:
* Engine speed
* Spark advance
* Throttle position
* Engine coolant temperature
* Engine runtime
* Park/neutral position
* Vehicle speed
The actual model is then compared to the expected exhaust energy model.
Conditions for Running the DTC
* The engine is running, and a cold start has been detected.
* Vehicle speed is less than 3 km/h (2 mph).
* The engine is at idle with no input from the accelerator pedal.
* The calculated catalyst temperature is less than 100掳C (212掳F).
* Engine coolant is greater than 10掳C (50掳F) and less than 56掳C (132掳F).
