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Pete, Technician
Category: Car
Satisfied Customers: 28768
Experience:  17 years automotive training and experience.
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Billy, Land Rover LR3, 2006 4.4ltr, Canada (But vehicle from

Customer Question

Hi Billy,Land Rover LR3, 2006 4.4ltr, Canada (But vehicle from the US).Just recently I have had a few fault codes pop up during the very cold weather (and usually just after start up). The sensors mentioned have all been recently replaced (for the fault I last spoke with you about) so I am pretty certain the sensors themselves are fine, but I was wondering if they share a common ground? Once reset, these fault codes do not appear until the vehicle has been restarted, and then not always. The O2 sensor seems to be the one which faults out most often, but usually with the P0134 (no activity code). Ignore the cat code -- that is rare and only occasionally occursI have (today) cleaned both battery terminals to ensure a good feed. Can you suggest anything else I should check?
Submitted: 1 year ago.
Category: Car
Expert:  Pete replied 1 year ago.

My name is ***** ***** I am a professional here at Just Answer. I noticed that your question had not received a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.

Inspect the wiring leading to the oxygen sensors for any issues.If any broken or corroded or damaged wiring is found leading to or at the oxygen sensors this will need to be corrected.I have found this as one of the main causes for this type of fault here.If this was already checked and found o.k. let me know so we can continue.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 1 year ago.
Hi Pete,Yeah, the wiring is fine and the O2 sensor, MAS, MAP, temp. sensor, and thermostat housing were replaced 3 months ago for a different fault (turns out that they were replaced needlessly as the fault was something entirely different).With all these fault codes kicking off together, and with their being a low voltage issue, I'm pretty sure its a voltage supply issue. The feed is good, so I'd like to know if they share a ground -- and if they do, where that ground is located.Thanks, Pete
Expert:  Pete replied 1 year ago.

The only two sensors I see codes set for are the oxygen sensor bank 1 sensor 1 and the mass air flow sensor.The catalytic converter code can be a fault with the catalytic converter itself needing replaced as this is common to restrict and cause issues or if there are any exhaust leaks or damaged exhaust components needing replaced or repaired.In some cases repairing the oxygen sensor code issue here may resolve the catalytic converter code but I see the code is for bank 2 and the oxygen sensor codes are bank 1 so you may in fact need a new catalytic converter.

The ground control comes from the engine computer for the oxygen sensor as well as the signal wires.The only outside wire for the oxygen sensors is the green wire which feeds voltage to the sensor from the 20 amp fuse 14E in the battery junction box fuse panel.

The mass air flow sensor all wires lead to the engine control module as well with no seperate ground wire.The ground is fed from the engine computer on the purple wire to the mass air flow sensor.The signal wires are the light green and blue wires and the voltage comes in on the tan wire from fuse 10E which is a 15 amp fuse.

I see this as a possible oxygen sensor fault (even though it was replaced it may be faulty again if it failed prematurely) or an issue with the engine computer and a catalytic converter fault.

Thanks Pete

Customer: replied 1 year ago.
Hi Pete,Yeah -- I have known about the cat. code for a while now, but the performance has been measured externally by Land rover and internally by an exhaust engineer (when we fitted the O2 sensor the O2 bung needed replaceing -- there was no melting of the cat, and it looked in good condition), and seems to be related to my changing banks 1 and 2 sensor 1 O2 sensors, but not sensor 2 O2 sensors. The coolant temperature sensor is also playing up and occasionally does not send information to the gauge (or sends improper info to the gauge). Restarting the car fixes that issue. The temp sensor codes are thrown at the same time as the other codes and almost as often (the one snap shot just happened not to have that code on there).The engine ECM was recently checked and flashed (again due to the fault 3 months ago), and is fine -- the ECM was checked for internal water damage and has worked fine for the last 3 months -- it is only in this very cold weather that I have been seeing these 'phantom' faults thrown.The engine ECM for this vehicle only provides grounds to the various sensors by linking them to the various ground points on the frame -- it sort of collates the grounds in the ECM and then routes that ground to the sensor. There are numerous ground points all over the passenger (LHD) side of the vehicle, and each ground point only provides grounds to a few sensors. Thank you for helping me with the wire colours to the sensors -- those will be helpful, but I would also like to know where the ground points are that the ECM switches for those few items at issue.When last I had a problem with the fuel supply, Billy (a justanswer tech) was able to provide me with the ground points for the ECM as they fed different sensors -- and, in that case, fuel pump feed. These ground points are all over the passenger side of the vehicle, and require different parts of the vehicle to be taken off to get at the different ground points. Because more than one system (sensor) is throwing these faults and because all of these sensors were recently replaced (as well as others not throwing codes) with genuine Land Rover parts, I believe that the common issue is one of power supply (as all of the systems are not otherwise related). Consequently, I don't believe that it could be a sensor fault (mostly because 4 brand new genuine LR sensors do not fail at the same time).Finding the ground locations for those sensors (via the ECM) would help me in that I would only have to remove certain body panels and fixtures to check/clean that particular ground. (For instance, there are three behind the front passenger headlight, three under the dust shield above the passenger front wheel, three in the engine bay, and others dotted all over the vehicle).I did not take a snapshot of the code reader showing the temp. code, but the fault code shows 'out of range coolant temperature reading'. However, turing off the ignition and restarting makes the temp sensor operate properly -- making me think again that there is an impedance in ground or feed to the sensors exacerbated by the recent snow and cold temperatures we are having currently. I have checked all of the wiring and multiplugs to all of the sensors and there is no greening or issues with the wiring at the sensor end and I have cleaned and re-installed the battery terminals themselves.Hope this helps.....
Expert:  Pete replied 1 year ago.

This is a difficult question for me to answer myself here.

I will open your question up for others here to see if someone else can assist further on this as there may be others here that may have more info on what to check or do with this issue.I hope you can get this resolved with ease.No need to reply to my last post here unless it is a last resort as it will keep your question locked to me and others will not be able to view it.If you feel you want to continue to work with me on this feel free to reply at any time but keep in mind in some cases it can be difficult to fully diagnose or help repair this without seeing your vehicle.

Thanks Pete

Customer: replied 1 year ago.
Thanks, ***** ***** is there any way to put this question to Billy, the Land Rover tech who helped me last time? I did hit the 'ask me again' function, but I received an answer from you.
Expert:  Pete replied 1 year ago.

I have opted out so if Billy sees this hopefully he will help on this here or any other Land Rover expert here.

Thanks Pete

Customer: replied 1 year ago.
Ok! Super -- thanks for your help, Pete. I hope you have a great New Years celebration! All the best!
Expert:  Pete replied 1 year ago.

Your welcome.Happy New Years to you as well.

Thanks Pete