DTC P1127: Fuel Control: Condition

DTC P0127 indicates that HO2S heater was not on during KOER self-test and testing of HO2S did not occur. Possible cause is cool exhaust system. Only use this test to diagnose the following:

HO2S and sensor connection.
Vacuum systems.
Fuel injector and/or fuel injector circuitry.
Powertrain Control Module (PCM).
Electrical circuits (HO2S, HO2S GND, INJ 1-8, VPWR and SIG RTN).

NOTE: HO2S may be displayed on scan tool as 02S.

To prevent replacement of good components, be aware, the following non-EEC areas may be cause of driveability concerns:

Ignition system.
Faulty evaporative emission system.
EGR and/or PCV system.
Air intake system.
Engine oil contamination.
Fuel system.
Exhaust system leaks or restriction.
Engine cooling system.

Connect scan tool to DLC. Using scan tool, access all HO2S HEATER PIDS. If all PIDs indicate ON, repeat QUICK TEST. See TESTS W/CODES - INTRODUCTION article. If any PIDs are off, operate engine until all PIDs are on. Repeat QUICK TEST.