Circuit Description
The powertrain control module (PCM) continuously monitors the oxygen sensor (O2S) activity for 100 seconds. During the monitor period, the PCM counts the number of times that the O2S switches from rich to lean and from lean to rich and adds the amount of time it took to complete all switches. With this information , an average time for all switches can be determined. If the average time to switch is too slow, a DTC P0133 will set.
If the oxygen sensor pigtail wiring, connector, or terminal are damaged, the entire oxygen sensor assembly must be replaced. DO NOT attempt to repair the wiring, connector, or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained by way of the oxygen sensor wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degrade oxygen sensor performance. Refer to Section 8A-5, Heated Oxygen Sensor (O2S) Repair.
Conditions for Setting
| • | When one or more of the following DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0441, P0562, P563, P1171, P1441 are not present. |
| • | The average O2S 1 response times are greater than 249 ms for rich to lean sweeps or 249 ms for lean to rich sweeps. |
| OR |
| • | Ratio of response times is greater than 3.5 or less than 0.8. |
| • | The engine speed is between 1,825-2,275 RPM. |
| • | TP angle is between 8-14 percent. |
| • | Evaporative Emissions Control System is commanded open for greater than 35.5 percent PWM. |
| • | Purge Learned Memory is greater than approximately 128. |
Action Taken
| • | Malfunction indicator lamp (MIL) illuminates after one driving cycle with the fault active. |
| • | Vehicle will operate in Open Loop. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after passing three consecutive diagnostic tests. |
| • | A history DTC will clear after 40 consecutive ignition cycles have occurred without a fault. |
| • | History and current DTCs can be cleared by using a scan tool. |
Diagnostic Aids
The DTC P0133 or slow response is most likely caused by one of the following:
| • | Fuel pressure--The system will go rich if pressure is too high. The PCM can compensate for some increase, however, if it gets too high a DTC P0133 will be set. Refer to Fuel System Diagnosis . |
| • | Leaking injector--A leaking or faulty 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--Inspect 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 contamination--Inspect the O2S 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, a rich exhaust indication. The PCM will then reduce the amount of fuel delivered to the engine causing a severe surge or driveability problem. |
Step | Action | Values | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||||
1 | Was the On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | |||||||||||
2 | Are any component DTCs set? | -- | Go to component DTC charts | Go to Step 3 | ||||||||||
3 |
Do the parameters show averages less than the specified values or ratios outside the specified values? | 249 ms 249 ms 3.5, 0.8 | Go to Step 4 | Go to Diagnostic Aids | ||||||||||
4 | Visually and physically inspect the following items:
Was a problem found in any of the above areas? | -- | Go to Step 9 | Go to Step 5 | ||||||||||
5 | Check the exhaust manifold for an exhaust leak near the engine. Repair as necessary. Was an exhaust leak found? | -- | Go to Step 3 | Go to Step 6 | ||||||||||
6 |
Does the scan tool voltage indicate voltage within the specified range? | 407-509 mV | Go to Step 7 | Go to Step 10 | ||||||||||
7 |
Does the scan tool voltage indicate voltage below the specified value? | 200 mV | Go to Step 8 | Go to Step 11 | ||||||||||
8 |
Important: Before replacing sensors, the cause of the contamination must be determined
and corrected
Replace the O2S. Is the action complete? | -- | -- | |||||||||||
9 | Repair the condition as necessary. Is the action complete? | -- | -- | |||||||||||
10 | Repair the O2S 1 signal circuit for a short to ground. Is the action complete? | -- | -- | |||||||||||
11 |
Does the O2S 1 voltage measure above the specified value? | 407 mV | Go to Step 12 | Go to Step 13 | ||||||||||
12 |
Was an O2S 1 low circuit problem found and corrected? | 5ohms | Go to Step 14 | |||||||||||
13 |
Was an O2S 1 signal circuit problem found and corrected? | 5ohms | Go to Step 15 | |||||||||||
14 | Inspect the O2S 1 low circuit terminal connection at the PCM and replace the terminal if necessary. Did the terminal require replacement? | -- | Go to Step 16 | |||||||||||
15 | Inspect the O2S 1 signal circuit terminal connection at the PCM and replace the terminal if necessary. Did the terminal require replacement? | -- | Go to Step 16 | |||||||||||
16 | Replace the PCM. Is the action complete? | -- | -- | |||||||||||
