DTC P1133 O2S Insufficient Switching Sensor 1. Isuzu S/T Isuzu

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 1999 🢒 S/T Isuzu - 4WD 🢒 DTC 🢒 DTC P1133 O2S Insufficient Switching Sensor 1

Engine Controls Components
Cell 20: EGR Valve, EVAP and IAC Controls
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

Circuit Description

The 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.

•	The engine coolant temperature (ECT) is more than 75°C (167°F).

•	The engine speed is between 1800 RPM and 2300 RPM.

•	The engine is operating in closed loop.

•	The throttle position (TP) angle is between 8 percent and 15 percent.

•	The evaporative emissions control system is commanded open for more than 80 percent.

•	The purge learned memory is more than approximately 0.86.

•	The diagnostic completes when 30 seconds of 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 to 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 - 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 number(s) below refer(s) to the step number(s) on the Diagnostic Table.

The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when this DTC set. The scan tool stores this data for later reference.

Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communication System (ITCS) procedures for PCM reprogramming and the Crankshaft Position System Variation Learn for the crankshaft position system variation learn procedure.

If no malfunctions are present at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.

DTC P1133-Oxygen Sensor (O2S) Insufficient Switching (Sensor 1)

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Turn ON the ignition switch leaving the engine OFF.
Install a scan tool.

Are any component DTCs set?

Go to Component DTC table

Go to Step 3

Start the engine.
Idle the engine at the normal operating temperature.
Operate the vehicle within the Conditions for setting this DTC as specified in the supporting text.
Monitor the Lean/Rich Transition and Rich/Lean Transitions while recording the number of switches.

Do the parameters show fewer transitions than the specified values?

30-40

Go to Step 4

Go to Step 18

Turn OFF the ignition switch.
Visually/physically inspect the following items:

•	Check to see that the O2S 1 is securely installed.

•	Check for corrosion on the terminals.

•	Check for terminal tension at the following connections:

-	O2S 1 electrical connector

-	PCM electrical connector

•	Check the O2S 1 ground circuit for a good connection.

•	Check for any damaged wiring.

Was a problem present in any of the above areas?

Go to Step 9

Go to Step 5

Start the engine.

Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

Check the exhaust manifold for an exhaust leak near the engine
Repair the leak as necessary.

Was a repair necessary?

Go to Step 3

Go to Step 6

Turn OFF the ignition switch.
Disconnect the O2S 1 electrical connector at the sensor.
Turn ON the ignition switch leaving the engine OFF.

Does the scan tool voltage indicate the O2S 1 voltage within the specified value?

407-509 mV

Go to Step 7

Go to Step 10

Connect a jumper wire between the O2S 1 high circuit (PCM side) signal circuit to ground.

Does the scan tool voltage indicate that the O2S 1 voltage is below the specified value?

200 mV

Go to Step 8

Go to Step 11

Turn OFF the ignition switch.

Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

Replace the Oxygen Sensor (O2S 1). Refer to the Oxygen Sensor Replacement .

Notice: Determine and correct the cause of the contamination in order to prevent damage to the replacement sensors.

•	Fuel contamination

•	Use of improper RTV sealant

•	Engine oil/coolant consumption

Is the action complete?

Go to Step 17

Repair the condition as necessary.

Is the action complete?

Go to Step 17

Turn OFF the ignition switch.
Repair the O2S 1 signal circuit for a short to ground. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 17

Remove the jumper wire.
Measure the voltage between the O2S 1 high signal circuit and ground using a DMM.

Does the O2S 1 voltage measure above the specified value?

407 mV

Go to Step 12

Go to Step 13

Turn OFF the ignition switch.
Disconnect the PCM electrical connectors.
Check the O2S 1 low circuit for continuity.
If the O2S 1 low circuit measures over the specified value, repair the following conditions:

•	Open circuit

•	Poor electrical connector

Was an O2S 1 low circuit problem found and corrected?

5ohms

Go to Step 17

Go to Step 14

Turn OFF the ignition switch.
Disconnect the PCM electrical connectors.
Check the O2S 1 signal circuit for continuity.
If the O2S 1 low circuit measures over the specified value , repair the following conditions:

•	Open circuit

•	Poor electrical connection

Was an O2S 1 signal circuit problem found and corrected?

5ohms

Go to Step 17

Go to Step 15

Check the O2S 1 low circuit terminal connection at the PCM.
Repair the terminal as necessary. Refer to Wiring Repairs in Wiring Systems.

Did the terminal require replacement?

Go to Step 17

Go to Step 16

Check the O2S 1 signal circuit terminal connection at the PCM.
Repair the terminal as necessary. Refer to Wiring Repairs in Wiring Systems.

Did the terminal require replacement?

Go to Step 17

Go to Step 16

Replace the PCM. Refer to the Powertrain Control Module Replacement .

Is the action complete?

Go to Step 17

Using the scan tool, clear the DTCs.
Start the engine.
Idle the engine at the normal operating temperature.
Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has ran and passed?

Go to Step 18

Go to Step 2

Check to see if any additional DTCs are set.

Does the scan tool display any DTCs that you have not diagnosed?

Go to applicable DTC table

System OK

Go to Diagnostic Aids