DTC P1138 or P1158. Cadillac XLR 2005

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2005 🢒 XLR 🢒 Accessories 🢒 Navigation Systems 🢒 DTC P1138 or P1158

Circuit Description

The heated oxygen sensor (HO2S) produces a voltage that varies between 100-900 mV under normal operating conditions. The engine control module (ECM) produces a bias voltage on the HO2S signal circuit of 420-480 mV. The reference ground for the sensor is provided through the ECM. The ECM monitors the signal voltage to determine if the exhaust is lean or rich. The oxygen sensor voltage is high when the exhaust is rich, and low when the exhaust is lean. The ECM constantly monitors the HO2S signal during the Closed Loop operation. If the ECM detects an HO2S voltage that stays above a specified value during a fuel cutoff condition, DTC P1138 will set for bank 1 sensor 2, or DTC P1158 will set for bank 2 sensor 2.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

•	DTC P1138 HO2S Circuit High Voltage During Decel Fuel Cut-Off (DFCO) Bank 1 Sensor 2

•	DTC P1158 HO2S Circuit High Voltage During Decel Fuel Cut-Off (DFCO) Bank 2 Sensor 2

Conditions for Running the DTC

•

DTCs P0036, P0037, P0038, P0056, P0057, P0058, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0137, P0138, P0139, P0140, P0141, P0157, P0158, P0159, P0160, P0161, P0201-0208, P0300, P0301-0308, P0442, P0443, P0446, P0449, P0453, P0454, P0455, P0458, P0459, P0496 are not set.

•	The calculated catalytic converter temperature is more than 650°C (1,724°F).

•	DTC P1138 or P1158 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The affected HO2S voltage parameter is more than 30 mV for more than 5 seconds during a decel fuel cut-off condition.

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

Values

Yes

Schematic Reference: Engine Controls Schematics

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

Allow the engine to reach normal operating temperature. Refer to Scan Tool Data List .
Quickly cycle the throttle from closed throttle to wide open throttle (WOT), 3 times within 5 seconds while observing the HO2S Bank 1 Sensor 2 or HO2S Bank 2 Sensor 2 parameter, with a scan tool.
Observe the HO2S Bank 1 Sensor 2 or HO2S Bank 2 Sensor 2 parameter with a scan tool.

Does the voltage react instantly when performing the above action?

Go to Step 4

Go to Step 3

Observe the Freeze Frame/Failure Records for this DTC.
Turn OFF the ignition for 30 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) 2.
Turn ON the ignition, with the engine OFF.
Measure the voltage from the HO2S high signal circuit, on the engine harness, side to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage more than the specified value?

475 mV

Go to Step 7

Go to Step 5

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

Is the voltage less than the specified value?

25 mV

Go to Step 6

Go to Step 8

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

Is the voltage less then the specified value?

25 mV

Go to Step 12

Go to Step 9

Measure the voltage from the HO2S low signal circuit, on the engine harness side connector, to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage more than the specified value?

50 mV

Go to Step 10

Go to Step 11

Test the HO2S high signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

Test the HO2S low signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

Test the HO2S low signal circuit for a short to voltage. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

Test the HO2S high signal circuit for a short to voltage or a short to the heater low control circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

The HO2S is detecting a rich exhaust condition or may be contaminated. Inspect for one of the following conditions:

•	HO2S connector water intrusion

•	A silicon-contaminated HO2S

•	Fuel-contaminated engine oil

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

•	Rich fuel injectors

•	An inaccurate mass air flow (MAF) sensor

Repair any of the above or similar engine conditions, as necessary.

Did you find and correct the condition?

Go to Step 17

Go to Step 13

Test for shorted terminals and poor connections at the HO2S. 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 17

Go to Step 15

Test for shorted terminals and poor connections at the engine control module (ECM). 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 17

Go to Step 16

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

Did you complete the replacement?

Go to Step 17

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

Did you complete the replacement?

Go to Step 17

Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 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 18

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