O2 Sensor
03-07-14, 06:18 PM
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O2 Sensor
Have had my first interesting problem with the HS since I bought it new back in 2010. At 58,000 miles had a check engine light come on. Of course I'm over the warranty so not covered by Lexus... The code was a P0136 (O2 Sensor, Bank 1, sensor 2) which is the downstream unit. Bought a replacement part from an autoparts warehouse and installed it. Reset code and was fine for about 20 miles...then I got a P0141 (same unit heater malfunction). Thinking I got a bad part, I contacted the supplier and the sent me a replacement unit for free. Put that unit in, cleared code and about 15 minutes after starting to drive, code returned. I can't believe that I got two bad units but I also don't think I have a bad wiring harness.
I've read on these forums that some advocate only buying the Denso O2 sensors as those are the same ones Lexus uses (even though they are more expensive). Anyone have any suggestions? I'm trying to avoid paying the dealership the $270 they want to replace the sensor....
I've read on these forums that some advocate only buying the Denso O2 sensors as those are the same ones Lexus uses (even though they are more expensive). Anyone have any suggestions? I'm trying to avoid paying the dealership the $270 they want to replace the sensor....
03-08-14, 12:56 AM
#2
Been having CEL issue w/ my V6 Camry and Denso sensors did not correct problem so YMMV. I think that MAF and IAC valve malfunction/dirty may somehow affect your O2 sensors. Nothing scientific to back me up but jus' a hunch. 58k does seem a bit low to have one go bad, especially since our engine does not run some of the time. A rumor I heard was that the use of regular gas reduces the lifespan on the sensors so this might also be whats happening, again YMMV. I always try and use gasoline w/ a decent cleaning agent like Chevron, Shell and recently Costco to keep varnish from forming. The Camry was second hand so not sure what was used beforehand and luckily in Hawaii we don't need to pass a smog test.
Not sure what the length of warranty coverage on O2 sensors are, as emissions warranty may apply so I would look into that first.
Not sure what the length of warranty coverage on O2 sensors are, as emissions warranty may apply so I would look into that first.
03-08-14, 03:50 AM
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Thanks. Already checked, emissions warranty doesn't cover O2 sensors. Interesting that you think the Denso units don't make a difference. I have always used decent gas with a cleaning agent, so I don't think that's the problem and all other car indications are fine. Appreciate the tips and am open to any others from the group...
03-08-14, 08:41 AM
#4
Mine went bad around the same time - 2010, 54k miles. I first misread the warranty and thought the emissions covered all related ignition parts, so I took it to the dealer. Wrong - they charged me an hour of labor to "verify" the code! I looked into doing it myself, but it looked like a PITA having to remove carpet and such so I paid the penance and had the dealer do it - $330 on top of the $130 already sunk to read the code. I did check with an independent shop that was hybrid certified and they wanted $400 with no guarantee they'd even use the right part.
I use regular gas - mostly BP as that's what's local to me. Never heard of that causing a problem downstream of the engine, given everything should be burned (including any cleaning agents) by then. I've only heard of cleaning agents working on intake/ fuel injectors / intake valves. But who knows - I too felt this was a bit early for a sensor to go bad on an otherwise pampered (I even take it to the dealer for 5K intervals) car that sits in an insulated garage every night.
Well, good luck! Maybe there's a source of discount Lexus parts online. I use handa.com for factory Honda/Toyota parts and accessories at 20% discount, but I didn't see this O2 sensor there.
I use regular gas - mostly BP as that's what's local to me. Never heard of that causing a problem downstream of the engine, given everything should be burned (including any cleaning agents) by then. I've only heard of cleaning agents working on intake/ fuel injectors / intake valves. But who knows - I too felt this was a bit early for a sensor to go bad on an otherwise pampered (I even take it to the dealer for 5K intervals) car that sits in an insulated garage every night.
Well, good luck! Maybe there's a source of discount Lexus parts online. I use handa.com for factory Honda/Toyota parts and accessories at 20% discount, but I didn't see this O2 sensor there.
03-08-14, 03:13 PM
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Thanks. Actually no need to remove the carpet in the HS250h. The Bank 2 sensor 2 sensor is right by the catalytic converter and the plug for it is also in the undercarriage...
03-10-14, 02:12 PM
#6
Been having CEL issue w/ my V6 Camry and Denso sensors did not correct problem so YMMV. I think that MAF and IAC valve malfunction/dirty may somehow affect your O2 sensors. Nothing scientific to back me up but jus' a hunch. 58k does seem a bit low to have one go bad, especially since our engine does not run some of the time. A rumor I heard was that the use of regular gas reduces the lifespan on the sensors so this might also be whats happening, again YMMV. I always try and use gasoline w/ a decent cleaning agent like Chevron, Shell and recently Costco to keep varnish from forming. The Camry was second hand so not sure what was used beforehand and luckily in Hawaii we don't need to pass a smog test.
Not sure what the length of warranty coverage on O2 sensors are, as emissions warranty may apply so I would look into that first.
Not sure what the length of warranty coverage on O2 sensors are, as emissions warranty may apply so I would look into that first.
Your dealer may be the way to go as I assume their computer can discern the correct problematic component or have them at least check to make sure the MAF sensor is operating correctly. Had a '02 RX that threw a CEL at 80k (never got a chance to get it diagnosed, my son totaled the car) and the Camry was bought with 105k with the CEL already lit. I had changed one of the O2 sensors using a Denso and the ECT sensor twice on the Camry with no changes on the codes. The MAF had to be cleaned at about 50k on the RX because it couldn't keep running on idle. Can't remember if that threw a CEL.
Hopefully for you the correct code is displayed or that the MAF sensor is bad/dirty. Also note that a sensor can be changed and the CEL cleared but soon come back on after a couple of days of driving, even w/ a different code. If this happens I would highly suspect the MAF or dirty IACV.
FYI, the Camry's MAF was an easy replacement (cleaning did not produce significant results) and used Seafoam to clean the IACV. Sincere best wishes for a speedy and inexpensive repair.
03-10-14, 03:45 PM
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Thanks for the info. Was the MAF issue on a Camry hybrid (same engine as the HS)? Where is it located (I'm assuming on top of the engine downstream of the inlet air filter)?
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03-11-14, 05:43 AM
#8
The MAF sensor should be located between your air cleaner and the throttle body. In our case it's attached to the air cleaner housing on the air outlet end going towards the throttle body. Its held in place w/ 2 phillips head screws and a wiring harness attached to it.
Sometimes the MAF can be cleaned (I use CRC brand MAF Sensor Cleaner) and re-installed. If the thin resistor wires inside are damaged then replacement is likely. Make sure it is COMPLETELY air dried before re-installation. Costs for a new one can be high so best to shop around, the cleaner can be had for less than $10. On a side note I don't recommend using K&N type air filters that utilizes a type of oil to aid in filtration. There could be some of this oil dislodging from the filter and eventually end up contaminating the resistor wires.
Like Magellan55 said his O2 sensor went bad so its not a sure bet on it being the MAF. If me, I would try cleaning the MAF first then clear the code(s). If the exact same code(s) come back then I would think about taking it to a dealer or someone that can guarantee their work and have them check it out. If the code(s) change, I would suspect the MAF at least partially at fault.
03-14-14, 06:57 PM
#10
P0136 is a very common trouble code with Toyota's. It's always the O2 sensor. I don't know of too many people that I know that have a Toyota product that didn't have this same code. It seems to be always the number 2, or aft sensor, and I can't figure out why. Replace the O2 sensor, reset the code, if it comes back, it's most likely the wiring or the plug.
The MAF has it own set of trouble codes and the 2 most likely are not interconnected. When the MAF is dirty, or broken or the connector came off, you'll get a different code which will direct you to the MAF. You might also notice your car idle rough and run real bad. You won't notice much issues with the O2 sensor. The rear one anyways. The front O2 sensor is a whole different matter.
The MAF has it own set of trouble codes and the 2 most likely are not interconnected. When the MAF is dirty, or broken or the connector came off, you'll get a different code which will direct you to the MAF. You might also notice your car idle rough and run real bad. You won't notice much issues with the O2 sensor. The rear one anyways. The front O2 sensor is a whole different matter.
03-14-14, 08:00 PM
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I'm really thinking it is the O2 sensor or the plug. The fact the first fault code I saw was bad O2 sensor and (upon replacement) fault shifted to the bad rear O2 sensor heater element seems to indicate either bad O2 sensor (and replacement) or the wiring/plug...
Besides replacing the O2 sensor, any suggestions on how to troubleshoot the plug?
Besides replacing the O2 sensor, any suggestions on how to troubleshoot the plug?
03-15-14, 04:42 AM
#12
O2 heater malfunction can be checked w/ a multimeter. Didn't want to go here because not sure what the parameters of the resistance should be and which terminals are to be used inside the plug. I think normally under 20 ohm resistance and contacts #1 and 2 . If you can find out this info you can check the sensor.if its working or not. As you said, it could be the wiring, but what confuses me is the P0136 code then P0141. If the wiring then the code shouldn't change.
03-15-14, 06:39 AM
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Totally agree. At this stage I'm hoping it is the sensor. Just got a new OEM one from lexusparts.com (seemed to be the cheapest source). Am going to install it. If that doesn't solve it, I'm thinking it might be the connector on the wiring harness...perhaps intermittent contact issue. Before I install the new sensor, will run some electrical contact cleaner on the harness connector and see if that makes a difference...
Will report back later today! Appreciate all the tips and help.
Will report back later today! Appreciate all the tips and help.
03-15-14, 11:59 AM
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Just an update (hopefully the final one in this thread) for the group.
Replaced the replacement O2 sensor (2nd one) with a genuine Lexus/Toyota part (which I believe is actually manufactured by Delco) and cleared the alarm codes. Have driven 17 miles since (three drive cycles) without the light coming back on. Unless it does return, I'm assuming this fixed the problem.
A summary of what happened, what I did and what seemed to work:
1. At 58,000 miles the check engine light came on. Pulled the Code and it was a P0136 code (Bank 1, sensor 2). On the HS, this sensor can be accessed from beneath the car and screws into the exhaust piping downstream of the catalytic converter. Unlike other Lexus cars, it has a quick-connect coupling to the wiring harness immediately above the exhaust system (below/behind the engine) so you don't have to pull carpeting on the inside of the car or anything.
2. Dealership wanted $175 for the part and $90 for one hour's labor to swap it out.
3. I shopped around and bought an OEM equivalent part from ******************.com. Part I ordered was WREPT960903ATP for $91 (counting tax, free shipping).
4. Received part, installed it and cleared the two codes in the car (P0136 and P0136 pending). Within 20 miles, the check engine light came on. Pulled code and it was now P0141 (Bank 1, Sensor 2 heater malfunction).
5. Spoke to some folks who all agreed that sometimes you get a "bad O2 sensor" (either the heater element or the sensor element), contacted auto parts warehouse and they shipped me a replacement unit free of charge (along with free shipping to return the defective unit.
6. Installed the 2nd replacement unit and cleared the codes (again there were two P0141 codes in memory, one active, one pending) - less than 15 minutes after starting car, check engine light came on (P0141).
7. Had read on another forum some people suggest that the Lexus cars are sensitive to the voltage on the O2 sensors and that best luck was had using Denso parts. At this stage my thought was the odds of getting two bad parts from auto warehouse were slim and that (best case) it was just that the "equivalent part" is close but not quite right. Worst case, I had a wiring harness or connector problem. So wanting to eliminate any other variables, I decided to pay for a genuine Lexus part and not even mess with getting a Denso from somewhere else. I ordered an O2 sensor (p/n 89465-75010) from lexuspartsnow.com for $144.63 (plus $15 for shipping). Still a bit cheaper than the dealer, but not much.
8. Swapped out the O2 sensor for the third time and cleared the error codes (again, 2 P0141 codes (one pending)). Check engine light hasn't come on to date.
While the electrical connector and O2 sensor screw threads were exact fits, the sensor head of the autowarehouse.com unit was slightly different than the Lexus/Toyota part I pulled from the car (which the lexus part I ordered matched exactly). Specifically the Lexus part has a row of small round holes around the head about 1/4 inch from the tip and three holes of the same size on the end (top) of the sensor head. The autowarehouse part had a row of oval slots around the head, no holes on the top. Obviously this should not make a difference in how the O2 sensor operates, but my theory is that the two sensor heads put out slightly different voltages or have different heater element resistance thus causing the P0141 error code I saw with the two equivalent parts. It may well be that you can order a Denso part from places and get exactly what the Lexus/Toyota part is, but I'm not sure on that.
Hope this helps others on the list...
Replaced the replacement O2 sensor (2nd one) with a genuine Lexus/Toyota part (which I believe is actually manufactured by Delco) and cleared the alarm codes. Have driven 17 miles since (three drive cycles) without the light coming back on. Unless it does return, I'm assuming this fixed the problem.
A summary of what happened, what I did and what seemed to work:
1. At 58,000 miles the check engine light came on. Pulled the Code and it was a P0136 code (Bank 1, sensor 2). On the HS, this sensor can be accessed from beneath the car and screws into the exhaust piping downstream of the catalytic converter. Unlike other Lexus cars, it has a quick-connect coupling to the wiring harness immediately above the exhaust system (below/behind the engine) so you don't have to pull carpeting on the inside of the car or anything.
2. Dealership wanted $175 for the part and $90 for one hour's labor to swap it out.
3. I shopped around and bought an OEM equivalent part from ******************.com. Part I ordered was WREPT960903ATP for $91 (counting tax, free shipping).
4. Received part, installed it and cleared the two codes in the car (P0136 and P0136 pending). Within 20 miles, the check engine light came on. Pulled code and it was now P0141 (Bank 1, Sensor 2 heater malfunction).
5. Spoke to some folks who all agreed that sometimes you get a "bad O2 sensor" (either the heater element or the sensor element), contacted auto parts warehouse and they shipped me a replacement unit free of charge (along with free shipping to return the defective unit.
6. Installed the 2nd replacement unit and cleared the codes (again there were two P0141 codes in memory, one active, one pending) - less than 15 minutes after starting car, check engine light came on (P0141).
7. Had read on another forum some people suggest that the Lexus cars are sensitive to the voltage on the O2 sensors and that best luck was had using Denso parts. At this stage my thought was the odds of getting two bad parts from auto warehouse were slim and that (best case) it was just that the "equivalent part" is close but not quite right. Worst case, I had a wiring harness or connector problem. So wanting to eliminate any other variables, I decided to pay for a genuine Lexus part and not even mess with getting a Denso from somewhere else. I ordered an O2 sensor (p/n 89465-75010) from lexuspartsnow.com for $144.63 (plus $15 for shipping). Still a bit cheaper than the dealer, but not much.
8. Swapped out the O2 sensor for the third time and cleared the error codes (again, 2 P0141 codes (one pending)). Check engine light hasn't come on to date.
While the electrical connector and O2 sensor screw threads were exact fits, the sensor head of the autowarehouse.com unit was slightly different than the Lexus/Toyota part I pulled from the car (which the lexus part I ordered matched exactly). Specifically the Lexus part has a row of small round holes around the head about 1/4 inch from the tip and three holes of the same size on the end (top) of the sensor head. The autowarehouse part had a row of oval slots around the head, no holes on the top. Obviously this should not make a difference in how the O2 sensor operates, but my theory is that the two sensor heads put out slightly different voltages or have different heater element resistance thus causing the P0141 error code I saw with the two equivalent parts. It may well be that you can order a Denso part from places and get exactly what the Lexus/Toyota part is, but I'm not sure on that.
Hope this helps others on the list...
03-15-14, 02:27 PM
#15
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