• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
The engine control module (ECM) supplies a voltage near 450 mV between the heated oxygen sensor (HO2S) high signal circuit and the low reference circuit. The HO2S varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean. The ECM monitors and stores the HO2S voltage information. The ECM evaluates the HO2S voltage samples in order to determine the amount of time that the HO2S voltage was out of range. The ECM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range. The ECM test for the following conditions:
• | The ECM monitors the HO2S voltage to determine if the signal voltage goes below a predetermined threshold within a certain amount of time. If the ECM determines that the signal voltage remains above the threshold, the ECM will command the fuel system lean to determine if the HO2S signal voltage can be forced below the threshold within a certain amount of time. |
• | The ECM monitors the HO2S voltage during fuel cut-off to determine if the signal voltage is more than a predetermined threshold. |
• | Before the ECM can report DTC P2270 or P2272 failed, DTCs P0036, P0037, P0038, P0056, P0057, P0058, P0137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P0341, P0342, P0343, P0346, P0347, P0348, P0366, P0367, P0368, P0391, P0392, P0393, P0443, P0458, and P0459 must run and pass. |
• | DTCs P0461, P0462, P0463, P2066, P2067, and P2068 are not set. |
• | The engine is operating. |
• | The ignition voltage is greater than 10 volts. |
• | The rear HO2S are at operating temperature for more than 10 seconds. |
• | The fuel injectors are enabled. |
• | The long term fuel control is enabled. |
• | The mass air flow (MAF) sensor is more than 10 g/s. |
• | The MAF sensor is between 6-33 g/s for more than 3 seconds during the intrusive test. |
• | The accumulated air flow into the engine is more than 15 grams during the fuel cut-off event. |
• | DTC P2271 and P2273 runs continuously once the above conditions are met. |
The ECM detects that the rear HO2S voltage is more than 650 mV for more than 100 seconds, then an intrusive test is performed. The ECM will lean the fuel mixture up to -7 percent and then wait for 10 seconds at -7 percent. If the ECM detects that the HO2S voltage is still more than 650 mV, the ECM then tests the HO2S at the next decel fuel cut-off. If the ECM detects the HO2S voltage is more than 200 mV after 4 seconds or for a cumulative of 50 seconds in decel fuel cut-off, the DTC sets.
DTCs P2271 and P2273 are Type B DTCs.
DTCs P2271 and P2273 are Type B DTCs.
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
⇒ | If any of the listed DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis. |
⇒ | If the HO2S parameter does change abruptly while moving the related harnesses repair the circuit as necessary. |
⇒ | If more than 500 mV, test the signal circuit of the HO2S sensor for a short to voltage. If the circuit/connections test normal, replace the ECM. |
• | Rich fuel injectors--Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 . |
• | Water intrusion in the HO2S harness connector |
• | High fuel system pressure--Refer to Fuel System Diagnosis . |
• | Fuel that is contaminated--Refer to Alcohol/Contaminants-in-Fuel Diagnosis . |
• | A collapsed air intake duct |
• | A restricted air filter element |
• | Exhaust system restrictions |
• | Excessive fuel in the crankcase |
• | An engine mechanical condition--Refer to Symptoms - Engine Mechanical . |
⇒ | If you find any of the above conditions, repair as necessary. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for engine control module replacement, setup, and programming |