Circuit Description
When the vehicle is first started, the engine operates in an open loop operation, ignoring the oxygen sensor signal and calculating the air-to-fuel ratio based on inputs from the engine coolant temperature (ECT), the throttle position, and the manifold absolute pressure sensors only. The Powertrain Control Module (PCM) will begin by using the oxygen sensor signal to control the fuel delivery in a closed loop when the following conditions are met:
| • | The engine has run a minimum amount of time based on ECT at engine start-up. |
| • | The oxygen sensor (O2S 1) has a varying voltage output showing that it is hot enough to operate properly. |
| • | The ECT has increased a minimum amount based on the ECT at engine start-up. |
Conditions For Running The DTC
| • | DTCs P0107, P0108, P0117, P0118, P0122, P0123, P0131, P0132, P0134, P0201, P0202, P0203, P0204, P0300, P0325, P0336, P0440, P0442, P0446, P0502, P0601, P0602, P1441, or P1621 not set. |
| • | The engine has been running more than 180 seconds. |
| • | The engine speed is between 1200 RPM and 3400 RPM. |
| • | The throttle position (TP) angle is between 10 percent and 40 percent. |
| • | The engine coolant temperature ECT is more than 65°C (149°F). |
| • | The above conditions have been met for 2 seconds. |
Conditions For Setting The DTC
The engine is not in closed loop for 5 seconds out of 12.5 seconds.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the malfunction present. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers. |
| • | A history DTC stores. |
| • | The coolant fan turns ON. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
DTC P0133 or slow response is most likely caused by one of the following items:
| • | Fuel pressure -- The system will go rich if fuel pressure is to high. The PCM can compensate for some increase, however, if it gets too high, a DTC P0172 may set. Refer to the Fuel System Diagnosis . |
| • | Leaking injector -- A leaking or malfunctioning injector can cause the system to go rich. |
| • | MAP sensor -- An output that causes the PCM to sense a higher than normal manifold pressure, or a low vacuum condition, can cause the system to go rich. Disconnecting the MAP sensor will allow the PCM to set a fixed value for the MAP sensor. Substitute a different MAP sensor if the rich condition is gone while the MAP sensor is disconnected. |
| • | Pressure regulator -- Check for a leaking fuel pressure regulator diaphragm by verifying the presence of liquid fuel in the vacuum line to the fuel pressure regulator. |
| • | TP sensor -- An intermittent TP sensor output can cause the system to go rich due to a false indication of the engine accelerating. |
| • | O2S 1 contamination -- Inspect the O2S 1 for silicone contamination from fuel or the use of improper room-temperature vulcanizing (RTV) sealant. The O2S 1 sensor may have a white powdery coating, which will result in a high but false voltage signal indicative of rich exhaust . The PCM will then reduce the amount of fuel delivered to the engine and cause a severe surge or driveability problem. |
Test Description
The numbers below refer to the step numbers on the Diagnostic Table:
-
When the system is operating correctly the HO2S voltage should toggle above and below the specified values.
-
The specified value is what is measured on a correctly operating system.
-
The specified value is what is measured on a correctly operating system.
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||||||||
|
Important: If any other DTCs are set except for HO2S DTCs, refer to the other DTCs first before proceeding with this table.
Does scan tool indicate that the O2 voltage is more than or less than the specified values? | 400-500 mV | |||||||||
3 | Operate vehicle within Failure Records conditions. Does the scan tool indicate this DTC failed this ignition? | -- | Go to Diagnostic Aids | |||||||
4 | Inspect and test for the following:
Did you find and correct the condition? | -- | ||||||||
Is the voltage near the specified value? | 450 mV | |||||||||
Does the scan tool indicate O2 voltage at or near the specified value? | 0 mV | |||||||||
7 | Test the low circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||
8 | Test the signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||
9 | Test for faulty connections at the O2 sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||
10 |
Important: Determine the cause of contamination before replacing the sensor. Inspect and test for the following:
Replace the affected O2 sensor. Refer to Oxygen Sensor Replacement . Did you complete the repair? | -- | -- | |||||||
11 | Test for faulty connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||||||||
|
Important: Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | -- | ||||||||
13 |
Does the DTC reset? | -- | ||||||||
14 | Use the scan tool in order to check for DTCs. Does the scan tool indicate any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
