DTC P1161 HO2S Heater Control Circuit Bank 2 Sensor 2. Cadillac Catera 1999

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 1999 🢒 Catera 🢒 DTC 🢒 DTC P1161 HO2S Heater Control Circuit Bank 2 Sensor 2

Engine Controls Components
Cell 20: Heated Oxygen Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The 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 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 sensor's 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 greater than 9 volts.

•	The engine is running.

•	The sensor heater is on.

Conditions for Setting the DTC

A fault is detected in the heater control circuit.

Action Taken When the DTC Sets

The engine control module (ECM) illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.

Conditions for Clearing the MIL/DTC

•	The ECM turns off the MIL after 3 consecutive drive trips that the diagnostic runs and passes.

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

•	The ECM battery voltage is interrupted.

•	The scan tool clears the MIL/DTC.

Diagnostic Aids

Notice: Using the J 35616-A Connector Test Adapter Kit will prevent damage to the harness connector terminals.

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 Intermittents and Poor Connections Diagnosis in Wiring Systems.

Test Description

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

Multiple HO2S DTCs will set if the supply voltage to the sensor heaters is open.

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.

The ECM provides the reference ground for the oxygen sensor. A small amount of current will appear on this circuit when the ECM is operational. The measured resistance of the circuit will increase when the ECM is operational. This is considered normal.

Heated Oxygen Sensor (HO2S) Heater Circuit

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

Using the scan tool, observe the DTC information.

Are all of the HO2S heater DTCs 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 16

Go to Step 17

Inspect the exhaust system for leaks upstream from the affected oxygen sensor including the AIR distribution system.

Did you find an exhaust leak?

Go to Step 18

Go to Step 5

Important: The ignition must be OFF when connecting or reconnecting 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 a problem?

Go to Step 19

Go to Step 6

Turn the ignition ON leaving the engine OFF.
Using a J 35616-200 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 21

Turn OFF the ignition.
Connect a J 35616-200 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.

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 20

Go to Step 25

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

Does the test lamp illuminate or flash?

Go to Step 10

Go to Step 15

Turn OFF the ignition.
Disconnect the test lamp.

Important: Do not use the HO2S reference ground circuit for this test. The use of the reference ground circuit may produce inaccurate results.

Jumper the HO2S signal circuit to a known good ground.
Turn ON the ignition leaving the engine OFF.
Using the scan tool, monitor the HO2S voltage for the sensor that applies to this DTC.

Is the voltage at the specified value?

0 mv

Go to Step 11

Go to Step 14

Important: Make sure the ECM has shut down prior to measuring the reference ground circuit resistance. This can be verified by the loss of communication on the scan tool.

Turn OFF the ignition for 30 seconds.

Important: Do not use a test lamp to test the continuity of the reference ground circuit. Damage to the ECM will result.

Using the J 39200 DMM, measure the resistance of the HO2S reference ground circuit to battery ground.

Is the resistance of the circuit less than the specified value?

5 ohms

Go to Step 23

Go to Step 12

Disconnect the ECM connector (C1).
Test the HO2S reference ground circuit for an open or high resistance.
Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and repair a problem?

Go to Step 26

Go to Step 13

Measure the resistance from the ground stud at the ECM bracket to battery ground.

Is the resistance of the circuit less than the specified value?

5 ohms

Go to Step 24

Go to Step 22

Turn OFF the Ignition.
Remove the jumper from the signal circuit.
Disconnect the ECM connector (C1).
Test the HO2S signal circuit for an open or high resistance.
Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and repair a problem?

Go to Step 26

Go to Step 24

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 a problem?

Go to Step 26

Go to Step 24

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

Did you find and correct a problem?

Go to Step 26

Go to Diagnostic Aids

Locate and repair the open in the B+ circuit from the Engine Controls Power Relay to the splice for the oxygen sensors. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Go to Step 26

Repair the exhaust leak as necessary.

Is the repair complete?

Go to Step 26

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

Is the repair complete?

Go to Step 26

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

Is the repair complete?

Go to Step 26

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

Is the repair complete?

Go to Step 26

Repair the high resistance in the ECM ground circuit. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

Go to Step 26

Replace the HO2S. Refer to Heated Oxygen Sensor Replacement .

Is the replacement complete?

Go to Step 26

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

Did you find and correct a problem?

Go to Step 26

Go to Step 25

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 on the vehicle.

Replace the ECM. Refer to Engine Control Module Replacement/Programming .

Is the action complete?

Go to Step 26

Using the scan tool, clear the DTCs.
Start the engine.
Allow the engine to idle until the engine reaches the normal operating temperature.
Select DTC and the Specific DTC function.
Enter the DTC number that was set.
Operate the vehicle within the Conditions for Running this DTC until the scan tool indicates that the diagnostic Ran.

Does the scan tool indicate that the diagnostic Passed?

Go to Step 27

Go to Step 2

Does the scan tool display any additional undiagnosed DTCs?

Go to the applicable DTC table

System OK