DTC Advanced Diagnostics: P027E
DTC P027E:Cold Start Air Fuel Ratio Control System Command Lean

General Description



The cold start emission reduction strategy controls air fuel ratio to lean when the engine is started at cold condition to lower the emission while the catalyst is not warmed up enough. If the commanded air fuel ratio is too lean or too rich compared to the target air fuel ratio, the powertrain control module (PCM) detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Continuous
Sequence
None
Duration
10 seconds or more
DTC Type
Two drive cycles, MIL on

Enable Conditions
Condition
Minimum
Maximum
Duration of quick warm-up system operation after engine start-up
–
40 seconds
Engine coolant temperature [ECT SENSOR 1]
50 °F (10 °C)
122 °F (50 °C)
Throttle valve
Fully closed
Accelerator pedal position
Released
Other
Vehicle stopped
[ ]: HDS Parameter

Malfunction Threshold
The ratio of commanded air fuel ratio by target air fuel ratio is 0.87 or less.

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
PCM internal circuit failure

Confirmation Procedure
Operating Condition
1.
Leave the vehicle until the engine coolant temperature [ECT SENSOR 1] lowers to 122 °F (50 °C) or less.
2.
Start the engine, and let it idle for at least 10 seconds.

Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the 12 volt battery.