GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2006 🢒 Terraza - 4WD 🢒 DTC 🢒 DTC P1400

DTC Descriptor

DTC P1400: Cold Start Emission Reduction Control System

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

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 airflow
    • 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 2 km/h (1 mph).
    • The engine is at idle with no input from the accelerator pedal.
    • Airflow per cylinder is greater than 40 mg/cylinder.
    • DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0300, P0335, P0336, P0351, P0352, P0353, P0501, P0502, P0506, P0507, P0601, P0602, P0604, P0606, P0641, P0651, P1516, P1682, P2101, P2108, P2119, P2120, P2125, P2127, P2135, P2138, P2610, or U0107 are not set.
    • This DTC runs for 15 seconds within the first 2 minutes of start up. This diagnostic runs once per trip when a cold start has been determined.

Conditions for Setting the DTC

The actual exhaust energy model does not match the expected exhaust energy model.

Action Taken When the DTC Sets

DTC P1400 is a type A DTC

Conditions for Clearing the MIL/DTC

DTC P1400 is a type A DTC

Reference Information

Description and Operation

Powertrain Control Module Description

DTC Type Reference

    •  Powertrain Diagnostic Trouble Code (DTC) Type Definitions
    •  Diagnostic Trouble Code (DTC) Types

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Diagnostic Aids

Any loading of the engine that lowers engine RPM, such as with partial application of the clutch, A/C cycling etc. during the first 120 seconds of engine runtime may set this DTC.

Circuit/System Verification
  1. Allow the engine to cool.
  2. Start and idle the engine for at least 2 minutes.
  3. DTC P1400 should run and pass.

Circuit/System Testing
    • Inspect the air intake system for the following conditions:
       - Damage, restriction, or modification
       - Dirty or deteriorating air filter element
       - Crankcase ventilation system for correct operation--Refer to Crankcase Ventilation System Inspection/Diagnosis .
       - Water intrusion
       - Vacuum leak and other un-metered air downstream of the mass air flow (MAF) sensor
       - Intake manifold leak
    • Inspect the exhaust system for the following conditions:
       - Water intrusion
       - Exhaust leak
       - Damaged, restricted, modified or enhanced exhaust system--Refer to Symptoms - Engine Exhaust .
    • Inspect the engine mechanical for items that could alter the air flow into the combustion chamber. Refer to Symptoms - Engine Mechanical .

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.