Rick's Free Auto Repair Advice

P1400 Trouble Code

Diagnose and fix P1400 trouble code

If you have an engine coolant heater, read this GM service bulletin first

GM defines a P1400 as Cold Start Emission Reduction Control System. That may sound like Greek to you, but there’s a method to their madness. A catalytic converter must warm up sufficiently to process excess hydrocarbons. One way to do that is to increase idle speed and retard timing during a cold start. So the computer commands those parameter on cold start up and then monitors this data:

Engine speed
Spark advance
Throttle position
Engine airflow
Engine coolant temperature
Engine runtime
Park/neutral position
Vehicle speed

The computer runs the test for P1400 for 15 seconds within the first 20mins of start up every time it detects a cold start with vehicle speed less than 1-MPH, engine at idle with NO input from driver’s accelerator pedal and none of the following trouble codes active:

P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0220, P0222, P0223, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0335, P0336, P0351, P0352, P0353, P0501, P0502, P0506, P0507, P0601, P0602, P0603, P0604, P0606, P0607, P060D, P062F, P0641, P0651, P1101, P1516, P1682, P2101, P2119, P2120, P2122, P2123, P2125, P2127, P2128, P2135, P2138, P2176, P2610

NOTE: If you load the engine with partial clutch application or turn on the AC during the first 120 seconds after startup, you can set a P1400 trouble code.

How to diagnose P1400

This code is set because the computer has determined the actual exhaust energy model does not match the expected exhaust energy model.

Start by inspecting the air intake system for the following:

Damage, restriction or aftermarket modification (aftermarket cold air system)
Dirty or deteriorating air filter element
PCV Crankcase ventilation system for correct operation

Next, inspect for:

Water intrusion
Vacuum leak and other un-metered air downstream of the mass air flow (MAF) sensor
Intake manifold leak

Most common causes of P1400

Carbon buildup in throttle body

air induction service

Carbon buildup in an electronic throttle body

Worn spark plugs
Dirty or intermittent MAF sensor

©, 2017 Rick Muscoplat

Posted on by Rick Muscoplat


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