If trouble codes P0141 and P0161 are lighting up the check engine light in your Chevy Express or GMC Savana van, you've got an issue with the rear oxygen sensors' heaters.
In this tutorial, which I've written specifically for the 2003-2007 Chevy Express/GMC Savana with a 4.8L, 5.3L, or 6.0L engine, I'll walk you through the meaning of these two diagnostic trouble codes (DTCs) and the most common fixes to get them to go away.
Let's get started!
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- Chevrolet Express (1500) 4.8L, 5.3L: 2003, 2004, 2005, 2006, 2007
- Chevrolet Express (2500) 4.8L, 5.3L, 6.0L: 2003, 2004, 2005, 2006, 2007
- Chevrolet Express (3500) 4.8L, 6.0L: 2003, 2004, 2005, 2006, 2007
- GMC Savana (1500) 4.8L, 5.3L: 2003, 2004, 2005, 2006, 2007
- GMC Savana (2500) 4.8L, 5.3L, 6.0L: 2003, 2004, 2005, 2006, 2007
- GMC Savana (3500) 4.8L, 6.0L: 2003, 2004, 2005, 2006, 2007
WIRING DIAGRAM: The following wiring diagram may come in handy:
NOTE: The following tutorial will help you troubleshoot diagnostic trouble codes P0135 and P0155:
What Do Trouble Codes P0141 And P0161 Mean?
Trouble codes P0141 and P0161 are similar in definition as they both indicate a problem with the rear oxygen (O2) sensor heater for bank 1 and bank 2, respectively. Let's break it down a bit further:
P0141: Heater Circuit Malfunction (Bank 1, Sensor 2)
- Meaning: This code indicates an issue with the heater circuit of the oxygen sensor located downstream from the catalytic converter on the side of the engine where the number 1 cylinder is.
- Bank 1 Sensor 2 (B1S2) Location: This oxygen sensor is located after the catalytic converter that filters exhaust from the bank of cylinders on the driver's side (cylinders 1, 3, 5, and 7).
This O2 sensor monitors the oxygen content of the exhaust gas after exiting the catalytic converter, providing feedback to the powertrain control module (PCM) about the effectiveness of the catalytic converter (in filtering exhaust gases produced by Bank 1 cylinders). - Other Designations: The B1S2 oxygen sensor, or Bank 1 Sensor 2, is known by several different names. Here are the most common ones you'll encounter:
- Downstream Left Oxygen Sensor.
- Driver Side Rear Oxygen Sensor.
- Left Rear O2 Sensor.
- Bank 1 Post-Catalytic Converter Oxygen Sensor.
- Possible Causes:
- Faulty oxygen sensor (Bank 1, Sensor 2).
- Damaged wiring or connector to the sensor.
- Blown O2 sensor heater element circuit fuse.
- PCM malfunction (less common).
P0161: Heater Circuit Malfunction (Bank 2, Sensor 2)
- Meaning: This code indicates an issue with the heater circuit of the oxygen sensor located downstream from the catalytic converter on the side of the engine where the number 2 cylinder is.
- Bank 2 Sensor 2 (B2S2) Location: This oxygen sensor is located after the catalytic converter that filters exhaust from the bank of cylinders on the passenger's side of the van (cylinders 2, 4, 6, and 8).
This O2 sensor monitors the oxygen content of the exhaust gas after exiting the catalytic converter, providing feedback to the powertrain control module (PCM) about the effectiveness of the catalytic converter (in filtering exhaust gases produced by Bank 2 cylinders). - Other Designations: The B2S2 oxygen sensor, or Bank 2 Sensor 2, is known by several different names. Here are the most common ones you'll encounter:
- Downstream Right Oxygen Sensor.
- Passenger Side Rear Oxygen Sensor.
- Right Rear O2 Sensor.
- Bank 2 Post-Catalytic Converter Oxygen Sensor.
- Possible Causes:
- Faulty oxygen sensor (Bank 2, Sensor 2).
- Damaged wiring or connector to the sensor.
- Blown O2 sensor heater element circuit fuse.
- PCM malfunction (less common).
What Causes Trouble Codes P0141 And P0161?
The most common causes of trouble codes P0141 and P0161 are the failure of the O2 sensor's heater element and wiring problems, such as shorts or open circuits in the sensor's wiring harness.
- Heater Element Failure: The most common cause of trouble codes P0141 and P0161, is the failure of the heater element inside the O2 sensor. Over time, the heating element will fail due to the extreme temperatures it's exposed to within the exhaust system, leading to a loss of functionality.
- Wiring Problems: Wiring problems are also a common culprit for these trouble codes. The sensor's wiring can be prone to damage from exposure to heat, vibration, and other environmental factors. Wiring may become frayed, corroded, or damaged, leading to open or short circuits in the heater circuit. One common scenario is when the sensor's wiring touches the hot exhaust pipe or other components, causing a short circuit.
- Blown O2 sensor heater element circuit fuse: The heater element of the oxygen sensor requires 12 volts to function, which it receives from Fuse 39 (15A) located in the underhood fuse box. If this fuse blows, the heater element doesn't get power.
One common reason for this fuse to blow is when the sensor's wires come into contact with the hot exhaust pipe, causing them to melt and short circuit, thus blowing the fuse. - PCM malfunction: The PCM is responsible for activating the heater element of the oxygen sensor. While very rare, it's possible for the PCM to malfunction and not be able to activate the oxygen sensor heater.
What Does The O2 Sensor Heater Do?
Oxygen sensors are vital components of the engine management system on the Chevy Express (GMC Savana). They give the powertrain control module (PCM) critical feedback about the air-fuel mixture it's fine-tuning. The only 'hitch' is that they're only completely operational once they've reached a high enough temperature (typically between 600 to 800 °F).
This means that when the engine in your van is cold, the O2 sensors are not hot enough to activate or are slow to respond. So, the PCM relies on preset fuel maps and data from other sensors like the mass airflow sensor to control the air-fuel ratio.
Once the engine warms up and the sensors reach their operational temperature, they start providing accurate feedback on the oxygen levels in the exhaust. This enables the PCM to fine-tune the air-fuel mixture in real-time, leading to better better gas mileage and emissions control.
Although the oxygen sensors are exposed to the intense heat of the exhaust gas, it isn't enough to consistently get them to reach their optimal temperature. This is especially true during idling or low-load situations when the exhaust gas heat just isn't high enough to maintain the O2 sensors' high operating temperature.
So, to ensure consistent and rapid heating regardless of engine conditions, the sensors are equipped with internal heaters. These heaters, activated by the PCM during engine start-up, swiftly heat up the sensors.
Eventually, the heating elements in the oxygen sensors degrade due to the extreme temperatures they're creating and are exposed to, leading to issues like trouble codes P0141 and/or P0161 you're currently researching.
How To Resolve Trouble Code P0141 Or P0161
I can tell you that replacing the affected oxygen sensor is the most common approach to resolving trouble codes P0141 or P0161 on the Chevy Express or GMC Savana vans. Here are the three main reasons why:
- Simplicity: Swapping out the O2 sensor is generally a straightforward task. It doesn't demand advanced diagnostic equipment or specialized skills. For most folks, it's the quickest fix because it can be done swiftly and with minimal effort.
- Cost-Effectiveness: Compared to other components of the engine management system, O2 sensors are relatively inexpensive, typically ranging from $30 to $50. This affordability makes replacing them a financially viable solution.
- Diagnostic Challenge: Troubleshooting the heater circuit can be time-consuming and requires a professional-grade scan tool (the ones that run $3,000 or more), along with access to professional diagnostic information. For most folks (even some repair shops), it's more practical and cost-effective to start by replacing the affected sensor. If no other underlying issues are present, such as electrical wiring problems in the O2 sensor heater circuit, then replacing the sensor alone can resolve the problem cheaply.
Before replacing the affected oxygen sensor, I want to recommend that you first perform some easy basic checks to ensure a successful repair:
- Check Fuse 39: Begin by inspecting Fuse 39 (15A) in the underhood fuse box to confirm that it's not blown. If the fuse is blown, the oxygen sensor heater element won't get power and the sensor will malfunction.
- Inspect Wiring Harness: Next, visually inspect the oxygen sensor wiring harness wires. Look for any signs of damage, such as melted insulation or wires that are shorted together. Damaged wiring can lead to Fuse 39 blowing. If you find any issues with the wiring, address them first before installing the new oxygen sensor.
To see my oxygen sensor recommendations and where to buy them, go here: Where To Buy The O2 Sensor And Save.
Now, if replacing the sensor doesn't solve the problem, or you're gonna diagnose it first, the basic test procedure for testing the heater element typically involves the following steps:
- Visual Inspection: The sensor's wiring and connectors are visually inspected for any signs of damage such as frayed wiring, melted insulation (caused by contact with the exhaust pipe), or wiring that has shorted together. Any visual damage to the wiring should be noted as a potential cause of the heater circuit malfunction and trouble code.
- Confirming The Heater Element Is Getting Power: This involves checking that the heater element is receiving the proper voltage supply. This typically involves using a multimeter to measure the voltage between the wire of the connector that connects to the oxygen sensor fuse and Ground. The voltage should be around 12 volts when the ignition is on and the engine is off.
- Activating The Heater With A Scan Tool: If the visual inspection and voltage measurement do not reveal any issues, the next step is to command the heater circuit 'ON' using a professional technician level scan tool. This tool allows you to perform a functional test of the heater element by commanding it to turn on manually. This test verifies whether the heater circuit is capable of functioning properly when activated by the PCM.
Where To Buy The O2 Sensor And Save
When replacing the oxygen sensor, it's important that you identify the correct sensor based on its location in the exhaust system. You'll see the terms "Bank 1," "Bank 2," "downstream," and "rear" used to differentiate between sensors on different sides of the engine:
Remember, Bank 1 refers to the side of the engine where cylinder 1 is located, which in the Express/Savana vans, it's the driver's side (and includes cylinders 1, 3, 5, and 7). Bank 2 refers to the opposite side of the engine, the passenger side of the van, and includes cylinders 2, 4, 6, and 8.
Identifying the correct bank is crucial because there can be differences in the length of the oxygen sensor's wiring and its connector between the two banks.
Bank 1 Sensor 2 (Driver Side Downstream):
43%
Bank 2 Sensor 2 (Passenger Side Downstream):
6%NOTE: Not sure if the oxygen sensors listed above fit your particular vehicle? Don't worry, once you get to the site they'll make sure it fits by asking you the specifics of your particular vehicle. If it doesn't fit, they'll find you the right one.
More Chevy Express/GMC Savana Articles And Tutorials
You can find a complete list of articles and diagnostic tutorials for the V8 Chevy Express and GMC Savana here:
Here's a sample of the tutorials you'll find in the index:
- How To Test For The Fuel Pump (2008-2013 V8 Chevy Express, GMC Savana).
- How To Test For A Blown Head Gasket (2003-2013 V8 Chevy Express, GMC Savana).
- How To Diagnose An Engine Cranks But Does Not Start Problem (2003-2007 V8 Chevy Express, GMC Savana).
- How Can I Tell If The Automatic Transmission Is Bad? (2003-2013 Chevrolet Express, GMC Savana).
If this info saved the day, buy me a beer!
