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, then adds the amount of time that the O2S 1 took to complete all the switches. With this information, an average time for all switches can be determined. Whenever the average time to switch is too slow, a DTC P0133 will set.
Conditions For Setting The DTC
| • | DTCs P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0404, P0405, P0506, P0507, P1404, P1441 not set. |
| • | The average O2S 1 response times are greater than 249mS for rich to lean sweeps or 249mS for lean to rich sweeps. |
Or
| • | Engine speed is between 1600 RPM and 2600 RPM. |
| • | Throttle Position (TP) angle is between 8% and 20%. |
| • | Ratio of response times is greater than 3.5 or less than 0.4. |
| • | Evaporative emissions control system is commanded open for greater than 60%. |
| • | Purge learned memory is greater than approximately 191. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information. |
| • | A history DTC stores. |
Conditions for Clearing the MIL/DTC
| • | The malfunction indicator lamp (MIL) will turn OFF after 3 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:
| • | The fuel pressure - The system will go rich if the fuel pressure is to high. The PCM can compensate for some increase, if the fuel pressure gets too high, a DTC P0133 may set. Refer to Fuel System Diagnosis . |
| • | A leaking fuel injector - A leaking or faulty fuel injector can cause the system to go rich. |
| • | The 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. |
| • | The 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. |
| • | The TP sensor - An intermittent TP sensor output will cause the system to go rich due to a false indication of the engine accelerating. |
| • | The O2S 1 contamination - Inspect the 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
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.
-
Replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be preformed. Refer to the latest Isuzu Technical Communication System (ITCS) information for programming procedures and also refer to the Powertrain Control Module (PCM) .
-
If no malfunctions have been found at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.
Step | Action | Value(s) | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to | ||||||||||||
2 | Were any component DTCs set? | -- | Go to Component DTC tables | |||||||||||
3 |
Do the parameters show averages less than the specified values or ratios less than or greater than the specified values? | 249 ms 249 ms 0.4 3.4 | ||||||||||||
4 | Visually/physical inspect the following items:
Was a problem found in any of the above areas? | -- | ||||||||||||
5 | Check the exhaust manifold for an exhaust leak near the engine and repair as necessary. Was a repair necessary? | -- | ||||||||||||
6 |
Does the scan tool voltage indicate voltage within specified values? | 407-509 mV | ||||||||||||
7 |
Does the scan tool voltage indicate the voltage below the specified value? | 200 mV | ||||||||||||
8 | Replace the Oxygen Sensor (O2S 1). Notice: Determine and correct the cause of the contamination in order to prevent damage to the replacement sensors.
Is the action complete? | -- | -- | |||||||||||
9 | Repair the condition as necessary. Is the action complete? | -- | -- | |||||||||||
10 | Repair the O2S 1 sensor signal circuit for a short to ground. Is the action complete? | -- | -- | |||||||||||
11 |
Does the O2S 1 voltage measure above the specified value? | 407 mV | ||||||||||||
12 |
Was a repair necessary? | 5ohms | ||||||||||||
13 |
Was a repair necessary? | 5ohms | ||||||||||||
14 | Check the O2S 1 sensor low circuit terminal connection at the PCM and then replace the terminal if necessary. Did the terminal require replacement? | -- | ||||||||||||
15 | Check the O2S 1 sensor signal circuit terminal connection at the PCM and replace the terminal if necessary. Did the terminal require replacement? | -- | ||||||||||||
Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||||||||||||
17 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||||||||||||
Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK Refer to Diagnostic Aids |
