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-   -   P0135 and P0155 - Oxygen Sensor Heater Circuit Malfunction (http://www.gmtruckhq.com/diagnostic-trouble-codes-dtcs/p0135-p0155-oxygen-sensor-heater-circuit-malfunction-3935.html)

The Master 07-28-2006 12:41 PM

P0135 and P0155 - Oxygen Sensor Heater Circuit Malfunction
 
We put together the following information about the P0135 and P0155 fault codes. We have also included diagnostic procedures below that you can use in diagnosing/analyzing the code.

OBD II Fault Code

OBD II P0135
OBD II P0155

Fault Code Definition

The Power Train Computer or PCM has determined that the Oxygen Sensor has taken too long to begin switching after the Engine Coolant Temperature Sensor has reached its proper operating range, preventing closed loop fuel control.

OBD II P0135 Oxygen Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
OBD II P0155 Oxygen Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)

Symptoms
  • Check Engine Light will illuminate
  • Vehicle may idle or run rough
  • Decrease in fuel economy
  • Engine dies
  • Black smoke out of the exhaust and/or bad smelling exhaust
  • In some unusual cases, there are no adverse conditions noticed by the driver

Common Problems That Trigger the P0135 and P0155 Code
  • Defective Oxygen Sensor/Air Fuel Ratio Sensor Heater element(s)
  • Defective Oxygen Sensor/Air Fuel Ratio Sensor Heater circuit
  • Defective Engine Coolant Temperature Sensor
  • Defective sensor wiring and/or circuit problem
  • Defective Oxygen Sensor/Air Fuel Ratio Sensor Heater Relay or Fuse
  • PCM software needs to be updated
  • Defective PCM

Polluting Gases Expelled
  • HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
  • CO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas
  • NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog

Want to Learn More?

The purpose of codes P0135 and P0155 is to track the amount of time that the Oxygen Sensor or Air Fuel Ratio Sensor takes to go from indicating that the fuel control system is in open loop to rapidly switching above and below the 450 millivolt set point, thus indicating that the fuel control system is in closed loop. This time measurement begins after the Engine Coolant Temperature Sensor indicates that the engine has warmed up sufficiently. If the signal lingers or is set below the lean-to-rich cross-count point—generally around 450 millivolts for an Oxygen Sensor—then the code P0135 or P0155 is triggered.

The switching time of an Air Fuel Ratio Sensor can also be observed using a scanner, though this data is only an approximation created by the Power Train Control Module for diagnostic purposes. In order to set, this Oxygen Sensor/Air Fuel Ratio Sensor code usually requires malfunctions on two different drive cycles by the vehicle; however, if the problem is severe enough, the code can set in less than fifteen minutes on an initial test drive, after the clearing of all codes. In other words, the code setting criteria varies from vehicle to vehicle.

P0135 and P0155 Diagnostic Theory:
Oxygen Sensor Heater Circuit


When the code P0135 or P0155 is set, record the freeze frame data in fine detail. Next, duplicate the code setting conditions on a test drive, paying particular attention to load, MPH, and RPM. The best tool to use on this test drive is a data streaming scan tool that has factory quality and dedicated live data. Be sure to verify the code conditions before you advance to the next set of tests.

If You Cannot Verify the Code Setting Malfunction

If you cannot verify the code setting malfunction, then do a thorough visual inspection of the sensor, the connections, and the exhaust system. Verify that there are 12-volt heater signal(s) and good ground(s) to the sensor and that they follow the required times, per the manufacturer diagnostic documentation. Perform a resistance test on the Oxygen Sensor Heater Element and compare the reading to the manufacturer's specification. It should be well within the specification envelope.

Make sure that the Engine Coolant Temperature Sensor is reading well within the closed loop envelope and that its readings don't go below 160º F when the vehicle is driven, especially above 45 MPH. Verify that the signal from the Oxygen Sensor to the PCM is being "seen" by back probing the Oxygen Sensor connector and, if needed, back probing the signal wire at the PCM. Inspect the sensor harness to ensure that it isn't chafed and/or grounding anywhere and be sure to perform a wiggle test. You will want to use a high impedance Digital Volt Ohm Meter (DVOM) for all of these electrical tests. If you still cannot find a problem, then try these steps next:
  • If you can receive authorization from the customer to keep the vehicle overnight, clear the code and test drive the vehicle by driving it home and then back to work in the morning, making sure that you are duplicating the code setting driving conditions on both trips. If the code still does not come back, you can give the customer the option of replacing the Oxygen Sensor as a diagnostic step since the sensor is the most likely problem and the code will presumably set again. If the customer declines, then return the vehicle with a clear description of the inspections and your findings plainly attached to the final copy of the repair order. Keep another copy for your own records in case you have to re-visit this inspection for any reason.
  • If this is an inspection for an emissions failure, most government programs suggest that you replace the sensor as a preventative measure so the vehicle won't remain in a highly polluting operational condition. After the Oxygen Sensor is replaced, the monitors will have to be re-set and this, too, will test most phases of the Oxygen Sensor system to ensure that the problem was solved. Be sure to verify that the Mode 6 test IDs and component IDs that pertain to fuel control are well within the parameter limits. If there is a problem with re-setting the monitors, continue the inspection until you find the root cause of the problem.

If You Can Verify the Code Setting Malfunction

If you can verify the code setting malfunction, then do a careful visual inspection of the sensor, the connections, and the exhaust system. Make sure that there are no exhaust leaks upstream of the Oxygen Sensor. Verify that there are 12-volt heater signal(s) and good ground(s) to the sensor and that they follow the required times, per the manufacturer diagnostic documentation. Perform a resistance test on the Oxygen Sensor Heater Element and compare the reading to the manufacturer's specification. It should be well within the specification envelope.

Make sure that the Engine Coolant Temperature Sensor is reading well within the closed loop envelope and that its readings don't go below 160º F when the vehicle is driven, especially above 45 MPH. Verify that the signal from the Oxygen Sensor to the PCM is being "seen" by back probing the Oxygen Sensor connector and, if needed, back probing the signal wire at the PCM. Inspect the sensor harness to ensure that it isn't chafed and/or grounding anywhere and be sure to perform a wiggle test. You will want to use a high impedance Digital Volt Ohm Meter (DVOM) for all of these electrical tests. If you still cannot find a problem, then try these steps next:
  • The most comprehensive way to test and condemn an Oxygen Sensor Heater Circuit is to use a Dual Trace Labscope with the time division graticule set at 100-millisecond intervals and the voltage scale set at +/- 20 volts. Run the warmed-up vehicle with the Heater Voltage wire back probed on one channel and the Heater Ground wire on a second channel and verify that the Heater Circuit Voltage is applied at idle and the Heater Ground Circuit stays intact. Next, observe these readings while the engine speed is 2000 RPM. At 2000 RPM, most Oxygen Heater Circuits should not be putting the 12-volt signal to the Heater Element because the heat from the exhaust system should be sufficient enough to keep the Oxygen Sensor at operating temperature.
  • Next, perform a range test and time test, still using the Labscope. Run the engine at 2000 RPM and quickly close the throttle and then snap it back open. The Oxygen Sensor Signal needs to go from around 100 millivolts (when the throttle closes) to above 900 millivolts (when the throttle opens) in less than 100 milliseconds. A new sensor will do this test within these ranges in less than 30–40 milliseconds.
  • If the sensor fails either of the above Labscope inspections, most emissions programs will allow you to condemn the sensor because the slow switching time leads to high NOx levels and above-normal CO levels and HCs. This is because the Cerium bed of the OBD II Catalytic Converter is not being supplied with the proper amount of Oxygen each time the signal "lags" between the peaks and valleys of its sine wave.

Note: If the Oxygen Sensor signal ever goes to a negative voltage or above 1 volt, this alone is enough to condemn the sensor. These out-of-range readings are often caused by the Heater Circuit bleeding voltage or ground into the Oxygen Sensor signal circuit. They can also be caused by contamination or physical damage to the sensor.

If the above tests and inspections don't produce verifiable results, then physically remove the Oxygen Sensor. If the Sensor Probe has a white and chalky appearance, the sensor has been lagging between switching phases and needs to be replaced. It should have the light tannish coloration of a healthy spark plug.

Note: On some vehicles, there is an Oxygen Sensor Heater Circuit Relay that can fail or malfunction on an intermittent basis. Be sure to verify that this relay works perfectly. If you are going to replace the Oxygen Sensor, you should consider replacing the Heater Circuit Relay as a preventative measure because they commonly fail and are not very expensive or time-consuming to replace.

Watch This Video for an Understanding of What an Oxygen Sensor Signal Looks Like

P0135 and P0155 Diagnostic:

Air Fuel Ratio Sensor Heater Circuit

Most Air Fuel Ratio Sensors are basically two heated Oxygen Sensors that work in tandem in order to create a much faster responding Oxygen Sensor/Fuel Control System. These systems are also capable of "'broadband" operation, which means that the vehicle will remain in closed loop and maintain active long term and short term fuel control during wide open throttle conditions. A conventional Oxygen Sensor System cannot maintain fuel control when the throttle is above 50 percent and the vehicle is under heavy load, such as wide open throttle.

When the code P0135 or P0155 is set, record the freeze frame data in fine detail. Next, duplicate the code setting conditions on a test drive, paying particular attention to load, MPH, and RPM. The best tool to use on this test drive is a data streaming scan tool that has factory quality and dedicated live data. Be sure to verify the code conditions before you advance to the next set of tests.

If You Cannot Verify the Code Setting Malfunction

If you cannot verify the code setting malfunction, then do a thorough visual inspection of the sensor, the connections, and the exhaust system. Verify that there are 12-volt heater signal(s) and good ground(s) to the sensor and that they follow the required times, per the manufacturer diagnostic documentation. Perform a resistance test on the Oxygen Sensor Heater Element and compare the reading to the manufacturer's specification. It should be well within the specification envelope.

Verify that the signal from the Air Fuel Ratio to the PCM is being "seen" by back probing the signal wire(s) at the connector and if, needed, back probing the signal wire(s) at the PCM. Inspect the sensor harness to ensure that it isn't chafed and/or grounding anywhere and be sure to perform a wiggle test. You will want to use a high impedance Digital Volt Ohm Meter (DVOM) for all of these electrical tests. If you still cannot find a problem, then try these steps next:
  • If you can receive authorization from the customer to keep the vehicle overnight, clear the code and test drive the vehicle by driving it home and then back to work in the morning, making sure that you are duplicating the code setting driving conditions on both trips. If the code still does not come back, you can give the customer the option of replacing the Air Fuel Ratio Sensor as a diagnostic step since the sensor is the most likely problem and the code will presumably set again. If the customer declines, then return the vehicle with a clear description of the inspections and your findings plainly attached to the final copy of the repair order. Keep another copy for your own records in case you have to re-visit this inspection for any reason.
  • If this is an inspection for an emissions failure, most government programs suggest that you replace the sensor as a preventative measure so the vehicle won't remain in a highly polluting operational condition. After the Air Fuel Ratio Sensor is replaced, the monitors will have to be re-set and this, too, will test most phases of the sensor system to ensure that the problem was solved. Be sure to verify that the Mode 6 test IDs and component IDs that pertain to fuel control are well within the parameter limits. If there is a problem with re-setting the monitors, continue the inspection until you find the root cause of the problem.

If You Can Verify the Code Setting Malfunction

If you can verify the code setting malfunction, then do a careful visual inspection of the sensor, the connections, and the exhaust system. Make sure that there are no exhaust leaks upstream of the Air Fuel Ratio Sensor. Verify that there are 12-volt heater signal(s) and good ground(s) to the sensor and that they follow the required times, per the manufacturer diagnostic documentation. Perform a resistance test on the Air Fuel Ratio Heater Elements and compare the reading to the manufacturer's specification. It should be well within the specification envelope.

Verify that the signal from the Oxygen Sensor to PCM is being "seen" by back probing the Air Fuel Ratio Sensor connector and, if needed, back probing the signal wire at the PCM. Inspect the sensor harness to ensure that it isn't chafed and/or grounding anywhere and be sure to perform a wiggle test. You will want to use a high impedance Digital Volt Ohm Meter (DVOM) for all of these electrical tests.

There are numerous, complex tests for an Air Fuel Ratio Sensor, but these are the simplest and most time-efficient tests:
  • Air Fuel Ratio Senors may have several wires, but there are two key wires. Using a DVOM with the key on and the engine off, disconnect the sensor and probe the harness going to the PCM. Make sure one wire has 3.0 volts and another wire has 3.3 volts. The other wires are the 12-volt power(s) and ground(s) for the heater circuits. In some cases, you may have to start the engine and let it idle to find the proper voltages on all the wires.
  • Use jumper wires to connect the sensor to the harness. Connect your DVOM in series with the 3.3 volt wire. Turn your DVOM to the milliamp scale and start the engine, letting it idle. The 3.3 volt wire should cross-count between +/- 10 milliamps. Vary the RPM and as you add and decrease throttle, you should see the signal respond to subtle changes in mixture. If you don't consistently see the +/- 10 milliamp variation in this wire, then the Air Fuel Ratio Sensor is defective.
  • If all the above tests and inspections do not produce verifiable results, then physically remove the Air Fuel Ratio Sensor. If the Sensor Probe has a white and chalky appearance, the sensor has been lagging between switching phases and needs to be replaced. It should have the light tannish coloration of a healthy spark plug.


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