P0043 OBD-II Trouble Code: HO2S Heater Control Circuit Low (Bank 1 Sensor 3)

Our certified mechanics come to you · 12-month, 12,000-mile warranty

SCHEDULE P0043 DIAGNOSTIC Get a fair and transparent estimate upfront
Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0043 code

P0043 is a diagnostic trouble code (DTC) for "HO2S Heater Control Circuit Low (Bank 1 Sensor 3)". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
SCHEDULE P0043 DIAGNOSTIC Get a fair and transparent estimate upfront

P0042 code definition

P0042 stands for low circuit voltage for the heated oxygen sensor bank 1 sensor 2. This code can be seen with P0044 and P0042.

What the P0042 code means

The definition of P0042 is low voltage for the heater control circuit. P0042 indicates that the car’s ECU has detected lower than expected voltage and has triggered a warning light.

What causes the P0042 code?

P0042 may have a few typical causes:

  • Bank 1 sensor 2 has failed
  • Open or shorted wiring for bank 1 sensor 2
  • Poor electrical connection or high resistance
  • Internal ECU issues

What are the symptoms of the P0042 code?

The vehicle’s engine control unit (ECU) detects lower than specified voltage from bank 1 sensor 2’s heater circuit. This triggers the Check Engine Light to be illuminated on the dash. When the heater control circuit malfunctions, it causes readings to not be accurate for bank 1 sensor 2. In rare cases, the vehicle may experience rough running and poor fuel economy.

How does a mechanic diagnose the P0042 code?

As with most DTC’s, step-by-step diagnostics are required to rule out simple issues before looking at more complex ones. Repair steps are as follows:

  • A scan tool is installed into vehicles OBD-II port to check if P0042 is present

  • Freeze frame data is observed so conditions for the code being triggered can be recreated

  • The code is cleared and a test drive is performed under the same conditions as the freeze frame data indicated.

  • If the Check Engine Light returns upon test, then the code is confirmed.

  • The technician performs a visual inspection of wiring and bank 1 sensor 2 for any damage, breaks, or shorted wiring.

  • Bank 1 sensor 2 voltage is checked to make sure it is not excessively low.

  • If low voltage is confirmed, bank 1 sensor 2 is faulty

  • If low voltage was not present, a diagnostic of the ECU will be performed, this test is manufacture and vehicle-make specific.

Common mistakes when diagnosing the P0042 code

P0042 is an uncommon code. Following all steps and not skipping anything is important so nothing is overlooked. Oxygen sensors should not be cleaned, and if faulty, should be replaced. Always confirm low voltage for oxygen sensor bank 1 sensor 2 before any replacement is performed.

How serious is the P0042 code?

P0042 is generally not a serious code as it usually does not cause any symptoms other than the Check Engine Light. With poor fuel economy and the vehicle running roughly, it is recommended to have this code looked at by a qualified technician as soon as possible to ensure safe operation of the vehicle.

What repairs can fix the P0042 code?

The most common repairs are as follows:

Additional comments for consideration regarding the P0042 code

Though this code is more uncommon, it does occur periodically. Following all steps and not jumping to conclusions before checking is important to make fixing this code simple. Refer to manufacture diagrams for the wiring and sensor locations to aid in diagnostics.

Need help with a P0042 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6220.

trouble codes
P0043
Check Engine Light

Fast and easy Check Engine Light is on Inspection service at your home or office.

SCHEDULE P0043 DIAGNOSTIC
Get a fair and transparent estimate upfront

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

4,810

Rating Summary
4,424
187
47
28
124
4,424
187
47
28
124

Joel

19 years of experience
741 reviews
Joel
19 years of experience
Acura RL - Check Engine Light is on - Jacksonville, Florida
very knowledgeable and precise. able to fix electrical issues in my car. Right on time for the appointment.

Christopher

15 years of experience
41 reviews
Christopher
15 years of experience
Honda Accord - Check Engine Light is on - Fairburn, Georgia
Christopher was excellent! He explained everything in detail to make sure I understood. He was professional and provided me with the next course of actions to resolve my care issues. I'm glad he was sent to service my car.

Alexander

18 years of experience
58 reviews
Alexander
18 years of experience
Saab 9-7x - Check Engine Light is on - Kissimmee, Florida
He was very friendly and very helpful . I felt like it was being around a close friend , also gave me so very good advice on my car & future advice about it . Highly recommend mechanic, would use his services again .

Matthew

31 years of experience
639 reviews
Matthew
31 years of experience
Jeep Patriot - Check Engine Light is on - Norfolk, Virginia
Matthew was on time which was a relief, he is very knowledgeable and was easy to understand what was wrong and what was being done. I am recommending to friends and family due to the great experience Matthew gave me. Extremely professional 10/10

More related articles

P3411 OBD-II Trouble Code: Cylinder 2 Deactivation/Intake Valve Control Circuit Low
P3411 means the system detected a problem with vehicle sensors due to electrical problems, bad solenoids, low oil pressure, or mechanical issues.
What Gases Does the OBD Detect in the Exhaust?
Your Your engine runs on combustion – fire – which creates exhaust gases. A wide range of gases are produced during normal operation, and they must be controlled because many of them become pollutants when released into the atmosphere. It’s...
P0819 OBD-II Trouble Code: Up and Down Shift Switch to Transmission Range Correlation
P0819 means there is an issue a voltage or resistance problem with the transmission's up- and down- shift switch, likely due to a manufacturer fault.

Related questions

Check engine light - O2 sensor circuit + speed sensor circuit...

Hi there. O2 sensor low voltage can be caused my a number of things. Mass air flow sensor was only one of them. It can be a bad O2 sensor, coolant temperature sensor, or wiring issue. What should be...

P0045 code and acceleration problems

Hello. This is an issue is caused by a turbo boost control issue. Most of the time, it is caused by either a dirty air filter, a leak in the air intake system or the turbo actuator or the turbo...

Flashing check engine light after repairs

Hello Stephanie, thank you for writing in. Unfortunately your situation is complicated, and resolution may not be as easy as we would like. Due to the repairs they performed pertaining to the fuel, spark, and cooling system, it is difficult...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1-800-701-6230 · hi@yourmechanic.com