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
| • | No active MAP DTCs |
| • | No active IAT DTCs |
| • | No active ECT DTCs |
| • | No active TP DTCs |
| • | No active fuel trim DTCs |
| • | No active injector control DTCs |
| • | No active misfire DTCs |
| • | No active CKP DTCs |
| • | No active EVAP DTCs |
| • | No active IAC DTCs |
| • | No active PCM memory DTCs |
| • | ECT is more than 75°C (167°F). |
| • | Engine speed is between 1,800 RPM and 2,300 RPM. |
| • | Engine is operating in Closed Loop . |
| • | Throttle position (TP) angle is between 8 percent and 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. |
| • | Use a scan tool to clear the DTCs. |
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 it 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 -- Test for a leaking fuel pressure regulator diaphragm by inspecting 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 for proper circuit resistance between the O2S 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.
-
The replacement PCM must be programmed, and the Crankshaft Position System Variation Learn procedure must be performed.
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 Diagnostic Aids | |
4 |
The leak may be very small and typically be within 12 inches of the suspect O2S. 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 | ||
7 |
Did you find and correct the condition? | -- | ||
Connect a test lamp between the O2S LOW circuit at the PCM and battery positive. 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 |
