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).

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.