Circuit Description
When the vehicle is first started, the engine operates in an Open Loop operation, ignoring the oxygen sensor (O2S) signal and calculating the air/fuel ratio based on inputs from the engine coolant temperature (ECT), the throttle position (TP) and the manifold absolute pressure (MAP) sensors only. The powertrain control module (PCM) will begin by using the O2S signal for controlling the fuel delivery, 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 O2S 1 has a varying voltage output showing that the O2S 1 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-P0204, P0300, P0301-P0304, P0336, P0440, P0442, P0446, P0601, P0602, P1441, or P1621 are not set. |
| • | The engine has been running more than 250 seconds for an automatic transmission, or 230 seconds for a manual transmission. |
| • | The engine speed is between 1,200-3,400 RPM. |
| • | The TP angle is between 10-40 percent. |
| • | The ECT is more than 65°C (149°F). |
| • | 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 control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
Diagnostic Aids only talks about conditions causing a rich O2S. A lean O2S can also cause this diagnostic trouble code (DTC) for the same reason as rich.
An O2S performance or slow response DTC is most likely caused by one of the following items:
| • | Fuel pressure--The engine may run rich if the fuel pressure is too high. The PCM can compensate for some increase. However, if the fuel pressure is too high, a DTC P0172 may set. Refer to 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,low vacuum can cause the system to go rich. |
| • | Pressure regulator or restricted fuel filter--Inspect for a restricted fuel pressure regulator return hose by checking for a damaged or kinked hose between the fuel filter and the fuel tank. |
| • | A restricted exhaust system |
| • | 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 include leaking exhaust before O2S causing low reading, lean,--Inspect the O2S 1 for silicone contamination from fuel or the use of improper RTV sealant. |
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
When the system is operating correctly the O2S 1 voltage should toggle above and below the specified values.
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The specified value is what is measured on a correctly operating system.
-
The specified value is what is measured on a correctly operating system.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||
|
Important:: If any other DTCs are set, refer to the other DTCs before proceeding with this table.
Does the O2S 1 voltage read outside the specified range? | 400-500 mV | Go to Step 3 | Go to Step 4 | |||||||||
3 | Operate vehicle within the Failure Records conditions. Does the DTC reset? | -- | Go to Step 4 | Go to Diagnostic Aids | ||||||||
4 | Inspect and test for the following conditions:
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 5 | ||||||||
Does the O2S 1 signal voltage measure near the specified value? | 450 mV | Go to Step 6 | Go to Step 8 | |||||||||
Does the O2S 1 signal voltage measure near the specified value? | 0 mV | Go to Step 9 | Go to Step 7 | |||||||||
7 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||||||
8 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||||||
9 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||||||
10 |
Important:: Determine the cause of contamination before replacing the sensor.
Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||
11 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||||||
12 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||
13 |
Does the DTC run and pass? | -- | Go to Step 14 | Go to Step 2 | ||||||||
14 | With a scan tool, observe the stored information in Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||
