DTC P0134 HO2S Circuit Insufficient Activity Sensor 1. Chevrolet Impala 2000

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2000 🢒 Impala 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 DTC P0134 HO2S Circuit Insufficient Activity Sensor 1

Engine Controls Component Views
Engine Data Sensors-MAF, EVAP Vent, EVAP Purge, EGR
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The PCM supplies a bias voltage of about 450 mV between the HO2S signal and low circuits. When measured with a 10 megaohm DMM, this may display as low as 320 mV. The oxygen sensor varies the voltage within a range of about 1000 mV when the exhaust is rich, down through about 10 mV when exhaust is lean. The PCM constantly monitors the HO2S signal during Closed Loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If the HO2S 1 voltage remains at or near the 450 mV bias for an extended period of time, DTC P0134 will set.

Conditions for Running the DTC

•	No TP sensor, EVAP system, misfire, IAT sensor, MAP sensor, Fuel Trim, fuel injector circuit, EGR Pintle Position, ECT sensor, CKP Sensor, or MAF sensor DTCs present.

•	Engine run time more than 200 seconds.

Conditions for Setting the DTC

HO2S 1 signal voltage remains between 400 mV and 500 mV for more than 30 seconds.

Action Taken When the DTC Sets

•	The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.

•	The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

Conditions for Clearing the MIL/DTC

•	The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed.

•	The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

•	The DTC can be cleared by using a scan tool.

Diagnostic Aids

Check for the following conditions:

•	Poor connection or damaged harness -- Inspect the harness connectors for the following conditions:

-	Backed out terminals

-	Improper mating

-	Broken locks

-	Improperly formed or damaged terminals

-	Damaged harness

•

Malfunctioning HO2S heater or heater circuit -- With the ignition ON, engine not running, the HO2S voltage displayed on a scan tool should gradually drop to below 250 mV or rise to above 600 mV. If not, disconnect the HO2S and connect a test lamp between the HO2S ignition feed and heater ground circuits. If the test lamp does not illuminate, repair the open ignition feed or sensor ground circuit as necessary. Refer to Wiring Repairs . If the test lamp illuminates and the HO2S signal and low circuits are OK, replace the HO2S.

•	Intermittent test -- With the ignition ON, monitor the HO2S signal voltage while moving the wiring harness and related connectors. If the malfunction is induced, the HO2S signal voltage will change. This may help isolate the location of the malfunction.

If the DTC cannot be duplicated and is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set. Also refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table:

When the system is operating correctly the HO2S voltage should toggle above and below the specified values.

If the low circuit is shorted to ground the HO2S voltage will be less than 400 mV when the signal circuit is jumped to ground.

The specified value is what is measured on a correctly operating system.

This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.

P0134

Step

Action

Values

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

Important: If any other DTCs are set (except HO2S DTCs), refer to other DTCs first before proceeding with this table.

Engine at operating temperature.
Operate engine above 1200 RPM for two minutes.
With a scan tool, observe the HO2S voltage parameter.

Does scan tool indicate HO2S voltage varying outside the specified values?

400-500 mV

Go to Step 3

Go to Step 4

Operate vehicle within Failure Records conditions.

Does the scan tool indicate this DTC failed this ignition?

Go to Step 4

Go to Diagnostic Aids

Inspect and test for the following conditions:

•	Exhaust leak. Refer to Exhaust Leakage in Engine Exhaust.

•	The HO2S is installed correctly.

•	Damaged wiring. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 5

Turn ON the ignition.
Disconnect the HO2S.
Jumper the signal circuit (PCM side) to a good ground.
With a scan tool, observe HO2S voltage parameter.

Does the scan tool indicate HO2S voltage more than the specified value?

400 mV

Go to Step 6

Go to Step 10

Remove the jumper wire.
Measure the voltage on the HO2S signal circuit (PCM side) using a DMM that is connected to a good ground.

Does the voltage measure near the specified value?

4.5 V

Go to Step 7

Go to Step 9

Measure the voltage on the HO2S low circuit (PCM side) using a DMM that is connected to a good ground.

Does the voltage measure near the specified value?

5 V

Go to Step 11

Go to Step 8

Test the low circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 13

Test the signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 13

Test the low circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 14

Test for poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

Important: Determine the cause of contamination before replacing the sensor.

Inspect and test for the following conditions:

•	Fuel Contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis

•	Engine oil or coolant consumption. Refer to Oil Consumption Diagnosis in Engine Mechanical.

•

Use of improper RTV sealant. Refer to

Notice: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.

in Cautions and Notices.

Replace the effected HO2S sensor. Refer to Heated Oxygen Sensor Replacement .

Did you complete the repair?

Go to Step 15

Test for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 14

Important: The replacement PCM must be programmed.

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

Did you complete the repair?

Go to Step 15