Refer to
Oxygen Sensors
.
Circuit Description
The powertrain control module (PCM) continuously monitors the oxygen sensor 1 (O2S 1) activity for 100 seconds. During the monitor period, the PCM counts the number of times that the O2S 1 switches from rich to lean and from lean to rich. You can determine a total for all of the switches with this information. If the number of switches is too low, a DTC P1133 will set.
Conditions For Running The DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0200, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set. |
| • | ECT is more than 75°C (167°F). |
| • | Engine speed is between 1800-2300 RPM. |
| • | Engine is operating in Closed Loop. |
| • | The throttle position (TP) angle is between 8-15 percent. |
| • | Evaporative emissions control system is commanded open for more than 80 percent. |
| • | Purge learned memory is more than approximately 0.86. |
| • | Diagnostic completes when 30 seconds accumulated time has been spent in the above conditions. |
Conditions for Setting the DTC
The number of rich to lean counts is less than 1 or the lean to rich counts is less than 1.
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. |
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. |
| • | The MIL/DTCs can be cleared by using the scan tool. |
Diagnostic Aids
DTC P1133 is most likely caused by one of the following:
| • | Fuel pressure--The system will go rich if fuel pressure is too high. The PCM can compensate for some increase, however, if pressure gets too high a DTC P0172 will be 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. 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 sensor is disconnected. |
| • | Pressure regulator --Check for a leaking fuel pressure regulator diaphragm by checking for the presence of liquid fuel in the vacuum line to the regulator. |
| • | TP sensor --An intermittent TP sensor output will cause the system to go rich due to a false indication of the engine accelerating. |
| • | O2S 1 contamination --Inspect O2S 1 for silicone contamination from fuel or use of improper RTV sealant. The sensor may have a white powdery coating and result in a high but false voltage signal (rich exhaust indication). The PCM will then reduce the amount of fuel delivered to the engine causing a severe surge or driveability problem. |
Test Description
The numbers below refer to the step numbers on the diagnostic table:
-
This step tests for proper sensor activity. When in Closed Loop fuel control the HO2S voltage should rapidly swing above and below the bias voltage.
-
This step tests the PCM and the HIGH and LOW circuits between the PCM and the HO2S connector for proper operation.
-
This step tests for proper HO2S heater circuit operation up to the HO2S connector.
-
This step tests for proper circuit resistance between the HO2S LOW circuit and PCM ground.
-
Probable causes include the following: poor O2S LOW terminal contact at PCM, poor PCM ground connection, high PCM ground circuit resistance, and an ungrounded exhaust system.
-
This step tests for proper circuit resistance between the HO2S LOW circuit and PCM ground with a cold sensor. A loose HO2S or poor tread to exhaust electrical contact will cause higher resistance when the HO2S is cold. Although 500 ohms is allowed, typical resistance should be less than 50 ohms.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Does the O2S voltage read fixed within the specified value? | 300-600 mV | |||
3 | Were any other DTCs set? | -- | Go to applicable DTC | Go to Diagnostic Aids |
Did you find and correct the condition? | -- | |||
5 |
Does the voltage read less than the specified value? | 20 mV | ||
6 |
Does the resistance read less than the specified value? | 5 ohms | ||
Did you find and correct the condition? | -- | |||
Does the test lamp illuminate? | -- | |||
9 |
Does the resistance measure less than the specified value? | 5 ohms | ||
10 | Repair the circuit that measured high resistance. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
Repair the high resistance between the O2S LOW circuit and engine ground. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | ||
12 | Replace the O2S sensor. Refer to Oxygen Sensor Replacement . Did you complete the replacement? | -- | -- | |
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||
14 |
Does the DTC reset? | -- | System OK |
