DTC P0138 or P0158. GMC Truck Yukon

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon - 2WD 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 DTC P0138 or P0158

DTC P0138 or P0158 w/ Delphi HO2S

Circuit Description

This diagnostic applies only to vehicles built with Delphi heated oxygen sensors. To identify the heated oxygen sensor refer to

Oxygen Sensor Identification (4.8L/5.3L/6.0L)


(1)	Delphi Sensor - Case Grounded
(2)	Denso Sensor - Isolated Grounded

in Engine Controls Component Views.

The powertrain control module (PCM) supplies a voltage of about 450 mV between the heated oxygen sensor (HO2S) high and low signal circuits. The oxygen sensor varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The PCM monitors and stores the HO2S voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.

The PCM monitors the HO2S voltage for being fixed above a predetermined voltage. If the PCM detects the voltage is above a predetermined voltage, a diagnostic trouble code (DTC) sets.

Conditions for Running the DTC

•	DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0401, P0404, P0405, P0410, P0440, P0442, P0446, P0452, P0453, P1120, P1125, P1220, P1221, P1258, P1404, P1415, P1416, P1514, P1515, P1516, P1517, or P1518 are not set.

•	The air fuel ratio is between 14.5:1 and 14.7:1.

•	Vehicles without throttle-actuated control (TAC), the throttle position (TP) is between 3-70 percent.

•	Vehicles with throttle-actuated control (TAC), the throttle position (TP) indicated angle is between 3-70 percent more than the value observed at idle.

•	The loop status is closed.

•	The ignition 1 signal is between 9-18 volts.

•	The fuel tank level remaining is more than 10 percent.

•	Intrusive tests are not in progress.

•	Scan tool output controls are not active.

Conditions for Setting the DTC

The HO2S voltage is more than 930 mV for 200 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.

Diagnostic Aids

Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

•	Check the HO2S electrical connections for evidence of water intrusion. Water present in the connector causes the B+ supply to the heater to bleed over to the signal circuit.

•	Fuel pressure--The system goes rich if the pressure is too high. The PCM compensates for some increase. However, if the fuel pressure is too high, a DTC may set. Refer to Fuel System Diagnosis .

•	Rich injectors--Perform the Injector Balance Test. Refer to Fuel Injector Balance Test with Tech 2 or Fuel Injector Balance Test with Special Tool .

•	Leaking injector--Refer to the Fuel System Diagnosis . Refer to Fuel Injector Balance Test with Tech 2 or Fuel Injector Balance Test with Special Tool .

•	Fuel pressure regulator--Inspect the vacuum line going to the fuel pressure regulator for evidence of fuel. Refer to the Fuel System Diagnosis .

•	Evaporative emissions (EVAP) canister purge--Check the canister for fuel saturation. If full of fuel, check the canister control and hoses. Refer to Evaporative Emission Control System Description .

•

MAF sensor--Disconnect the MAF sensor and see if the rich condition is corrected. If so, check for proper installation. If installed correctly, replace the MAF sensor. If the MAF sensor is installed backwards, the system goes rich. The plastic portion of the sensor has arrows cast into it indicating proper air flow direction. The arrows must point toward the engine.

•	An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provides the supply of oxygen. Inspect the HO2S wires and connections for breaks or contamination. Refer to Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

•	TP sensor--An intermittent TP sensor output causes the system to go rich, due to a false indication of the engine accelerating. For an intermittent condition, refer to Intermittent Conditions .

Test Description

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

If the voltage is above the specified value the condition is present.

Jumpering the HO2S low signal circuit to ground is necessary for the PCM to correctly measure the voltage on the HO2S high signal circuit. If the HO2S voltage is within the specified range, the PCM and HO2S high signal circuit are OK.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Important: This diagnostic applies only to vehicles built with Delphi heated oxygen sensors. To identify the heated oxygen sensor, refer to

Oxygen Sensor Identification (4.8L/5.3L/6.0L)


(1)	Delphi Sensor - Case Grounded
(2)	Denso Sensor - Isolated Grounded

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Important: With the engine running, observe the front HO2S voltage using a scan tool. If the front HO2S voltage is fixed below 200 mV, refer to DTC P0131 or P0151 .

Allow the engine to reach operating temperature.
With a scan tool, observe the HO2S voltage for the sensor that applies to this DTC.

Is the HO2S voltage more than the specified value?

930 mV

Go to Step 4

Go to Step 3

Observe the Freeze Frame and/or Failure records data for this DTC.
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 or as close to the Freeze Frame and/or Failure records data that you observed.

Does the DTC fail this ignition?

Go to Step 4

Go to Diagnostic Aids

Turn OFF the ignition.
Disconnect the HO2S connector for the sensor that applies to this DTC.
Jumper the HO2S low signal circuit terminal on the engine harness side to a known good ground.
Turn ON the ignition, with the engine OFF.
Observe the HO2S voltage with a scan tool.

Is the HO2S voltage within the specified range?

350-550 mV

Go to Step 5

Go to Step 6

The HO2S may be detecting a rich exhaust condition or may be contaminated. Check for the following conditions:

•	Water intrusion into the HO2S connector

•	Silicone contamination of the HO2S

•	Engine oil contaminated by fuel

•	Incorrect fuel pressure

•	Rich fuel injectors

•	Inaccurate MAF sensor

•	EVAP canister purge condition

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

Did you find and correct the condition?

Go to Step 11

Go to Step 7

Turn OFF the ignition.
Disconnect the PCM connector that contains the HO2S high signal circuit. Refer to Powertrain Control Module Replacement .
Turn ON the ignition, with the engine OFF.
Test the HO2S high signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 8

Inspect for poor connections at the harness connector of 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 11

Go to Step 9

Inspect for poor connections at the harness connector of 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 11

Go to Step 10

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

Did you complete the replacement?

Go to Step 11

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 11

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 12

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

DTC P0138 or P0158 w/ Denso HO2S

Circuit Description

This diagnostic applies only to vehicles built with Denso heated oxygen sensors. To identify the heated oxygen sensor refer to

Oxygen Sensor Identification (4.8L/5.3L/6.0L)


(1)	Delphi Sensor - Case Grounded
(2)	Denso Sensor - Isolated Grounded

in Engine Controls Component Views.

The PCM monitors the HO2S voltage for being fixed above a predetermined voltage. If the PCM detects the voltage is above a predetermined voltage, a diagnostic trouble code (DTC) sets.

Conditions for Running the DTC

•	DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0401, P0404, P0405, P0410, P0440, P0442, P0446, P0452, P0453, P1120, P1125, P1220, P1221, P1258, P1404, P1415, P1416, P1514, P1515, P1516, P1517, or P1518 are not set.

•	The air fuel ratio is between 14.5:1 and 14.7:1.

•	Vehicles without throttle-actuated control (TAC), the throttle position (TP) is between 3-70 percent.

•	Vehicles with throttle-actuated control (TAC), the throttle position (TP) indicated angle is between 3-70 percent more than the value observed at idle.

•	The loop status is closed.

•	The ignition 1 signal is between 9-18 volts.

•	The fuel tank level remaining is more than 10 percent.

•	Intrusive tests are not in progress.

•	The scan tool output controls are not active.

Conditions for Setting the DTC

The HO2S voltage is more than 930 mV for 200 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.

•

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

Important: Never solder the HO2S wires. For proper wire and connector repair, refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Check the following items:

•	The fuel pressure--If the pressure is too high, the system will run rich. The PCM can compensate for some increase; however, if the pressure gets too high, this DTC may set. Refer to Fuel System Diagnosis .

•	A rich injector--Perform an Injector Balance test. Refer to Fuel Injector Balance Test with Tech 2 .

•	A leaking injector--Refer to Fuel System Diagnosis .

•	Fuel contaminated oil

•	EVAP canister purge--Check for a fuel saturation. If full of fuel, check the canister control and hoses. Refer to Evaporative Emission Control System Description .

•	Leaking fuel pressure regulator diaphragm by checking the vacuum line to the regulator for fuel.

•	The TP sensor--An intermittent TP sensor output causes the system to run rich due to a false indication of the throttle moving.

•	False rich indication due to silicon contamination of the heated oxygen sensor--This DTC, accompanied by a lean driveability condition and a powdery white deposit on the sensor, may indicate a false rich condition.

An intermittent may be caused by any of the following conditions:

•	A poor connection

•	Rubbed through wire insulation

•	A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

If a repair is necessary, then refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Test Description

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

Monitor the HO2S voltage of the opposite bank sensor. If the voltage activity of the opposite bank sensor is similar to the voltage activity of the suspect sensor, check for rich conditions that would affect both cylinder banks. An opposite bank sensor with normal HO2S voltage activity indicates the suspect HO2S is defective or a rich condition exists only on the suspect HO2S cylinder bank.

An HO2S contaminated by silicon will have a white, powdery deposit on the portion of the HO2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of unapproved silicon RTV engine gasket material or the use of silicon based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement HO2S will also get contaminated.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Important: This diagnostic applies only to vehicles built with Denso heated oxygen sensors. To identify the heated oxygen sensor, refer to

Oxygen Sensor Identification (4.8L/5.3L/6.0L)


(1)	Delphi Sensor - Case Grounded
(2)	Denso Sensor - Isolated Grounded

in Engine Controls Component Views.

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Run the engine until the engine reaches the normal operating temperature.
Using a scan tool, monitor the HO2S voltage for the sensor that applies to this DTC.

Is the HO2S voltage fixed more than the value specified?

930 mV

Go to Step 4

Go to Step 3

The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:

•	A signal wire intermittently shorted to voltage

•	HO2S connector water intrusion

•	A silicon contaminated HO2S

•	An intermittent rich engine condition such as the following:

-	EVAP canister purge condition

-	Fuel contaminated engine oil

-	Incorrect fuel pressure

-	A leaking fuel pressure regulator

-	Rich fuel injectors

-	An inaccurate MAF sensor

-	A rich engine condition during DFCO operation

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

Did you find and correct the condition?

Go to Step 10

Go to Diagnostic Aids

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

Is the HO2S voltage within the value range specified?

351-551 mV

Go to Step 5

Go to Step 6

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

•	HO2S connector water intrusion

•	Silicon contaminated HO2S

•	Fuel contaminated engine oil

•	EVAP canister purge condition

•	Incorrect fuel pressure

•	A leaking fuel pressure regulator

•	Rich fuel injectors

•	An inaccurate MAF sensor

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

Did you find and correct the condition?

Go to Step 10

Go to Step 8

Turn OFF the ignition.
Remove the jumper from the HO2S LOW reference circuit terminal.
Disconnect the PCM connector that contains the HO2S HIGH signal circuit.
Turn ON the ignition, with the engine OFF.
Using a DMM measure the voltage between the HO2S HIGH signal circuit PCM connector terminal and ground.

Is the voltage more than the specified value?

20 mV

Go to Step 7

Go to Step 9

Repair the short to voltage in the HO2S HIGH signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 10

Important: Before replacing a contaminated HO2S, determine and repair the cause of the contamination.

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

Did you complete the replacement?

Go to Step 10

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 10

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 11

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