DTC P0134 or P0154. Cadillac DeVille 2005

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2005 🢒 DeVille 🢒 Accessories 🢒 Navigation Systems 🢒 DTC P0134 or P0154

Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started, the powertrain control module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage once the sensor reaches operating temperature. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. If the PCM detects that the HO2S 1 voltage remains at or near the bias voltage amount, DTC P0134 will set for bank 1 sensor 1 or DTC P0154 will set for bank 2 sensor 1.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

•	DTC P0134 HO2S Circuit Insufficient Activity Bank 1 Sensor 1

•	DTC P0154 HO2S Circuit Insufficient Activity Bank 2 Sensor 1

Conditions for Running the DTC

•	DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0201-P0208, P0410, P0412, P0418, P0419, P0442, P0443, P0446, P0449, P0455 are not set.

•	The system voltage is between 10-18 volts.

•	The Engine Run Time parameter is more than 3 minutes and 20 seconds.

•	DTC P0134 and P0154 run continuously once the above conditions are met.

Conditions for Setting the DTC

The PCM detects that the HO2S 1 signal voltage remains between 350-500 mV for more than 60 seconds.

Action Taken When the DTC Sets

•	The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

•

The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

•	The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

•	A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

•	A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

•	Clear the MIL and the DTC with a scan tool.

Step

Action

Value(s)

Yes

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Start the engine.
Allow the engine to idle at operating temperature. Refer to Scan Tool Data List .
Clear the DTC and record the Freeze Frame/Failure Records.
Observe the affected HO2S 1 parameter with a scan tool.

Does the voltage fluctuate rapidly above and below the specified range?

350-500 mV

Go to Step 3

Go to Step 4

Observe the Freeze Frame/Failure Records for this DTC.
Turn OFF the ignition for 60 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 4

Go to Intermittent Conditions

Turn OFF the ignition.
Disconnect the affected heated oxygen sensor (HO2S) 1.
Turn ON the ignition, with the engine OFF.
Measure the voltage from the high signal circuit of the affected HO2S 1 on the engine harness side, to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage within the specified range?

400-500 mV

Go to Step 5

Go to Step 6

Connect a 3-amp fused jumper wire between the affected HO2S 1 high signal circuit and the affected HO2S 1 low signal circuit, on the engine harness side.
Observe the affected HO2S 1 parameter with a scan tool.

Is the voltage less than the specified value?

25 mV

Go to Step 9

Go to Step 8

Test the affected HO2S 1 high 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 14

Go to Step 7

Important: Disconnection of the powertrain control module (PCM) during testing may eliminate the voltage source that caused this fault.

Test the affected HO2S high signal circuit for a short to the affected HO2S heater low control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 11

Test the affected HO2S 1 low 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 14

Go to Step 11

Inspect for the following that may affect the HO2S operation:

Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.

•	HO2S for contamination

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

•	Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring

•	The HO2S must have a clean air reference in order to function properly. This clean air reference is obtained by way of the HO2S wires. Obstruction of the air reference and degraded HO2S performance could result from any attempt to repair the above conditions.

•	Exhaust system leaks or restrictions

•	Evaporative Emission (EVAP) System malfunction--Inspect the EVAP control system. Refer to Inspection/Maintenance Evaporative Emission System Set .

•	Incorrect fuel pressure--Refer to Fuel System Diagnosis .

Did you find and correct the condition?

Go to Step 14

Go to Step 10

Test for an intermittent and for a poor connection at the affected HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 12

Test for an intermittent and for a poor connection 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 14

Go to Step 13

Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section.

Replace affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 .

Did you complete the replacement?

Go to Step 14

Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 14

Clear the DTCs with a scan tool.
Turn OFF the ignition for 60 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 15

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK