DTC P0135 or P0155. Cadillac Catera 2001

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 Engine 🢒 Engine Controls - 3.0L (L81) 🢒 DTC P0135 or P0155

Circuit Description

The heated oxygen sensor (HO2S) heater circuit reduces the time required for the oxygen sensor to reach operating temperature and maintains the operating temperature during extended idle periods. When the ignition is turned to the ON position, voltage is supplied to the sensor heater from the engine controls power relay through a fuse. The engine control module (ECM) controls the heater operation by first modulating the ground circuit when the sensors are cold, and then turning the heaters ON continuously after a predetermined amount of time. This prevents the possibility of thermal shock to the sensor by controlling the sensors rate of heating. Once the sensor reaches operating temperature, the ECM may again modulate the ground.

Conditions for Running the DTC

•	The battery voltage is between 11-15.5 volts.

•	The engine is running.

•	The sensor heater is ON.

Conditions for Setting the DTC

The heater voltage is more than 3.6 volts, or less than 2.3 volts for more than 50 ms (0.05 seconds).

No system readiness is detected after 20 seconds of operation on a start occurring more than 4 minutes after the engine was last run.

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.

Diagnostic Aids

Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

An open fuse in the HO2S heater circuit may be caused by the heater element in one of the sensors. The condition may not be present until the sensor operates for a period of time. If no fault is present in the heater circuit, monitor the amperage of each heater using the DMM to determine if one of the heater elements is the cause of the open fuse.

Check for the following conditions:

•	The sensor pigtail or the harness may be mis-positioned and contacting the exhaust system.

•	An intermittent or poor connection or corrosion in the connector. 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.

Multiple diagnostic trouble codes (DTCs) will set if the supply voltage to the sensor heaters is open.

Any exhaust leak, even a small one, can affect the operation of the HO2S. The ECM compares the reading of sensor 1 to the reading of sensor 2 as part of the diagnosis. A leak between sensor 1 and sensor 2 may set a DTC.

The test lamp may illuminate or flash depending on the operating conditions. This indicates the ECM and the control circuit are functioning. The engine must be running for the ECM to operate the control circuit.

A short between the signal circuit and the reference ground circuit or the pump current input and output circuits may not appear on the voltage tests. The ECM must be disconnected and each circuit tested for continuity with the other HO2S circuits.

P0135 or P0155 Heated Oxygen Sensor (HO2S) Heater Performance Sensor 1

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Using the scan tool, observe the DTC information.

Are DTCs P0135, P0141, P0155, P0161, P1141 or P1161 set?

Go to Step 3

Go to Step 4

Turn OFF the ignition.
Inspect fuse 43 for the oxygen sensor heaters located in the ECM housing.

Is fuse 43 open?

Go to Step 19

Go to Step 20

Inspect the exhaust system for any leaks upstream from the affected oxygen sensor.
Inspect for any exhaust leaks between sensor 1 and sensor 2.
Repair the exhaust leak as necessary.

Did you find and correct the condition?

Go to Step 27

Go to Step 5

Important: The ignition must be OFF when disconnecting or connecting the HO2S electrical connector.

Turn OFF the ignition.
Disconnect the HO2S electrical connector.
Inspect both halves of the connector for any signs of corrosion or contamination.

Did you find the condition?

Go to Step 21

Go to Step 6

Turn ON the ignition, with the engine OFF.
Using a test lamp connected to ground, probe the switched B+ circuit at the ECM side of the oxygen sensor connector.

Does the test lamp illuminate?

Go to Step 7

Go to Step 23

Turn OFF the ignition.
Connect a test lamp between the switched B+ circuit and the heater control circuit at the ECM side of the oxygen sensor connector.
Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

Go to Step 8

Go to Step 9

Turn OFF the ignition.
Disconnect the ECM electrical connector C1.
With the test lamp still connected between the switched B+ and the control circuit.
Turn ON the ignition.

Does the test lamp illuminate?

Go to Step 22

Go to Step 26

Start the engine and allow the engine to idle.
Observe the test lamp.

Does the test lamp illuminate or flash?

Go to Step 10

Go to Step 18

Turn OFF the ignition.
Remove the test lamp.
Turn ON the ignition, with the engine OFF.
Measure the voltage of the HO2S signal circuit at the ECM side of the connector to battery ground.

Is the voltage within the specified range?

2-4 V

Go to Step 11

Go to Step 15

Measure the voltage of the HO2S reference ground circuit at the ECM side of the connector to battery ground.

Is the voltage within the specified range?

2-4 V

Go to Step 12

Go to Step 15

Measure the voltage of the HO2S pump current input circuit at the ECM side of the connector to battery ground.

Is the voltage within the specified range?

0.2-0.4 V

Go to Step 13

Go to Step 15

Measure the voltage of the HO2S pump current output circuit at the ECM side of the connector to battery ground.

Is the voltage within the specified range?

0.2-0.4 V

Go to Step 14

Go to Step 15

Turn OFF the ignition.
Disconnect the ECM connector C1.
Test each of the circuits on the affected HO2S for a short to each other.
Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 24

Is the voltage more than the specified value?

0.4 V

Go to Step 17

Go to Step 16

Test the affected circuit for the following conditions:

•

Open

•	Short to ground

•	High resistance

Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 25

Test the affected circuit for a short to voltage.
Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 25

Turn OFF the ignition.
Disconnect the ECM connector C1.
Test the heater control circuit for an open, high resistance, or a short to voltage.
Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 25

Test the switched B+ circuit for a short to ground.
Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Diagnostic Aids

Locate and repair the open in the switched B+ circuit from the engine controls power relay to the splice for the oxygen sensors. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

Repair or replace the terminal as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

Repair the short to ground in the heater control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

Repair the open in the B+ circuit from the splice to the oxygen sensor. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 27

Replace the HO2S. Refer to Heated Oxygen Sensor Replacement .

Did you complete the replacement?

Go to Step 27

Test for a poor connection or poor terminal tension at the ECM harness connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Repair as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 26

Important:

•	Perform the idle learn procedure when replacing the ECM.

•	This vehicle is equipped with a theft deterrent system that interfaces with the ECM. Program the new ECM with the frequency code of the theft deterrent module that is currently in the vehicle.

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the action?

Go to Step 27

Use the scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 28

Go to Step 2

With a scan tool, observe the stored information, Capture Info.

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

Go to Diagnostic Trouble Code (DTC) List

System OK