I just bought an 03 Spyder and the check engine light just came on. I took it to autozone and it says Heated Oxygen Sensor Heater Circuit Low Input. Is this bad?
elizabeth28
What was the actual code? It could be a bad O2 sensor or a broken wire...I've seen both (actually on my '03 Spyder that I just bought).
The tool to remove your O2 sensor is a 3/4 inch wrench...or a 19mm. Either should work...just disconnect the wires first so you don't twist them while you're unscrewing the O2 sensor. A loose sensor would likely give you a code, but not the heater circuit (normally). I had a pinhole leak right by the upstream O2 sensor that I installed a couple months back. It caused a CEL until I fixed it with high temp thermal epoxy.
The tool to remove your O2 sensor is a 3/4 inch wrench...or a 19mm. Either should work...just disconnect the wires first so you don't twist them while you're unscrewing the O2 sensor. A loose sensor would likely give you a code, but not the heater circuit (normally). I had a pinhole leak right by the upstream O2 sensor that I installed a couple months back. It caused a CEL until I fixed it with high temp thermal epoxy.
What happens when people who do not know what they're doing or do not have the right tools muck with the sensors is they damage the delicate wiring - I am not being facetious about little strands of 16 or whatever gauge wire being delicate - and then the heater circuit is damaged and then the check engine light comes on. You can diagnose by testing resistance across the two same-color wires of the sensor these are the heater circuit wires the the other two wires of different color are the signal wires. A. you should have continuity B. resistance should be something in the range 5 ohms but don't quote me on that go look it up. If either A or B is a fail then replace the sensor.
PS. So now in the spirit of contributing to the community here are some impromptu guidelines on handling O2 sensors:
a. Always disconnect the sensor from the harness and free its wiring from any restraints before you attempt to remove it.
b. Unless you're dead sure of yourself and what you're doing use a proper O2 removal socket with a slot for the wire these are available from any auto parts store.
c. Never apply any form of strain to the O2 sensor wires where they enter the sensor assembly this messes up the sensor almost surely i.e. guaranteed. In fact if you want to play a very mean and reprehensible joke on someone just apply a sharp tug to the wiring on their O2 sensors.
PS. So now in the spirit of contributing to the community here are some impromptu guidelines on handling O2 sensors:
a. Always disconnect the sensor from the harness and free its wiring from any restraints before you attempt to remove it.
b. Unless you're dead sure of yourself and what you're doing use a proper O2 removal socket with a slot for the wire these are available from any auto parts store.
c. Never apply any form of strain to the O2 sensor wires where they enter the sensor assembly this messes up the sensor almost surely i.e. guaranteed. In fact if you want to play a very mean and reprehensible joke on someone just apply a sharp tug to the wiring on their O2 sensors.
Good advice, for sure...but I've never been shy about taking things apart. Taking things apart and "just doing it" is how I learned most stuff (before the internet, even). Did I break things? Sure.
With Google's help, if you're careful and do a little research before starting, you'll very likely be fine. Maybe this comes with an assumption that someone is mechanically inclined...I don't know, I've always been so it just works out well for me.
Not saying the OP should undertake this (very minor) task, but I'm definitely not saying she shouldn't. A buddy of mine isn't a motorhead at all, and only in the last 2 years completely modified his Miata (full STR prep) all by himself. Coilovers, full exhaust, some wiring for an ECU, etc. Anyone can do anything if they're willing to learn.
With Google's help, if you're careful and do a little research before starting, you'll very likely be fine. Maybe this comes with an assumption that someone is mechanically inclined...I don't know, I've always been so it just works out well for me.
Not saying the OP should undertake this (very minor) task, but I'm definitely not saying she shouldn't. A buddy of mine isn't a motorhead at all, and only in the last 2 years completely modified his Miata (full STR prep) all by himself. Coilovers, full exhaust, some wiring for an ECU, etc. Anyone can do anything if they're willing to learn.
I’m not mechanically inclined yet, it’d be fun to learn. Right now I’m just freaked out abt driving it home (I’m 1100 miles away out of state & planning to drive it back)
My plan is to take it to a Toyota mechanic in the morning to see if they can remove the sensors to check the pre-cats.
The car is an 03 & in great shape so I took a chance at buying it even though they couldn’t get the 02 sensor off.
Now that it has that warning I’m getting really nervous though.
My plan is to take it to a Toyota mechanic in the morning to see if they can remove the sensors to check the pre-cats.
The car is an 03 & in great shape so I took a chance at buying it even though they couldn’t get the 02 sensor off.
Now that it has that warning I’m getting really nervous though.
You likely will be fine with driving while a CEL is on. At least for the code you reported. Typically you'll just get slightly worse gas mileage. The ecu defaults to a safe (rich mixture) when it detects a problem.
Regarding the concern about driving it.... You'll be fine. The O2 sensor heater circuit fault is not a factor on this car after it has warmed up.
More than likely the resistance is out of spec in the heater portion of the oxygen sensor. You need to get the car in the air and as mention above, measure resistance between the listed pins. Having the car on live data may show that the oxygen sensor is reading close or where it needs to be and you'll no doubt see the AF sensor is working properly. This is a common failure actually. I do one a week at the Toyota dealer. This week it's going to be three as I have a pair to do today. There are more checks that can be done, such as checking the inputs at the ecu to ensure its receiving proper communication from the oxygen sensor. But I'd ohm it out and see where it is. More than likely its just a bad sensor.
Without a bore scope I'm not sure how you will check the pre cats. Its not anything I'd really be concerned with anyways on a heater circuit failure.
Without a bore scope I'm not sure how you will check the pre cats. Its not anything I'd really be concerned with anyways on a heater circuit failure.
One other thing worth mentioning here...If you have access to the OBDII scanner from Autozone (or where ever), I'd clear the codes and see if they come back. If not, you're golden...if they do, then you can figure out your next step (likely O2 sensor replacement).
P0031 code means for the engine to run correctly, the engine exhaust must have a specific air-fuel ratio of 14.7 to 1 as signaled by the heated oxygen sensors (HO2S) which detect the oxygen content of the vehicle exhaust. This information is then sent to the Engine Control Module (ECM) to adjust the correct volume of fuel delivered to the engine. The sensor may have a bad heater element internally or it could have a bad ground, a failed 12 volt battery input or connector.
An HO2S is heated to insure very rapid signal data to the ECM closed loop system which helps control emissions during start-up and when the engine is cold or warming up.
It would have no impact on a fully warmed up engine. You should be able to drive for many miles once warmed up.
P0051 code definition
HO2S Heater Control Circuit Low (Bank 2 Sensor 1)
What the P0051 code means
This code is set when the car’s computer, or Engine Control Module (ECM), detects low system voltage in the heater control circuit. Specifically, the code is referencing Bank 2 Sensor 1. The heater circuit in the heated oxygen sensor is for warming the sensor before the vehicle reaches operating temperature for an accurate reading.
Looks like both A/F sensors are having issues, bank 1 and bank 2. Still once completely warmed up driving would be OK. Cold starts may be richer for a longer period of time which can wash the oil from the cylinder walls potentially causing wear. I prefer to fix issues quickly as I like my vehicles to run well.
O2 sensors last about 125k miles. They can be a bear to remove. Once removed you can visually check the top of the cat convert material in the precats. You can not see the bottom of the material from here.
An HO2S is heated to insure very rapid signal data to the ECM closed loop system which helps control emissions during start-up and when the engine is cold or warming up.
It would have no impact on a fully warmed up engine. You should be able to drive for many miles once warmed up.
P0051 code definition
HO2S Heater Control Circuit Low (Bank 2 Sensor 1)
What the P0051 code means
This code is set when the car’s computer, or Engine Control Module (ECM), detects low system voltage in the heater control circuit. Specifically, the code is referencing Bank 2 Sensor 1. The heater circuit in the heated oxygen sensor is for warming the sensor before the vehicle reaches operating temperature for an accurate reading.
Looks like both A/F sensors are having issues, bank 1 and bank 2. Still once completely warmed up driving would be OK. Cold starts may be richer for a longer period of time which can wash the oil from the cylinder walls potentially causing wear. I prefer to fix issues quickly as I like my vehicles to run well.
O2 sensors last about 125k miles. They can be a bear to remove. Once removed you can visually check the top of the cat convert material in the precats. You can not see the bottom of the material from here.
I had to recheck again because I have experienced a bad 02 sensor heater in the past with my 1ZZ.
When the car goes into limp mode it stays in limp mode until the code is reset and it will run slightly rich at all times which is bad. I remember this very well because I have driven my car until I received my replacement 02 sensors and although the car ran fine the millage suffered and the car smelled rich until I was able to replace the 02 sensors.
I have known about this from reading other information in the past specific to limp mode due to shorted heater circuit issues but I cannot source that information again readily. What I do know is that only the post cat 02 sensor will not cause the car into limp mode but the others will.
Here is the information I can provide that says it stays in limp mode running rich.
https://www.yourmechanic.com/article/p0030-obd-ii-trouble-code
https://www.yourmechanic.com/articl...-ii-trouble-code-ho2s-heater-control-circuit-low-bank-1-sensor-1-by-john-nelson
http://www.carobdcodes.com/toyota-p0030-ho2s-heater-control-circuit-bank-1-sensor-1.shtml
https://www.autocodes.com/p0135_toyota.html
If anyone has written information documented that says otherwise I would like to see it so I do not spread misinformation because I would hate for someone to receive bad advice that could penitently harm their engine.
When the car goes into limp mode it stays in limp mode until the code is reset and it will run slightly rich at all times which is bad. I remember this very well because I have driven my car until I received my replacement 02 sensors and although the car ran fine the millage suffered and the car smelled rich until I was able to replace the 02 sensors.
I have known about this from reading other information in the past specific to limp mode due to shorted heater circuit issues but I cannot source that information again readily. What I do know is that only the post cat 02 sensor will not cause the car into limp mode but the others will.
Here is the information I can provide that says it stays in limp mode running rich.
https://www.yourmechanic.com/article/p0030-obd-ii-trouble-code
https://www.yourmechanic.com/articl...-ii-trouble-code-ho2s-heater-control-circuit-low-bank-1-sensor-1-by-john-nelson
http://www.carobdcodes.com/toyota-p0030-ho2s-heater-control-circuit-bank-1-sensor-1.shtml
https://www.autocodes.com/p0135_toyota.html
If anyone has written information documented that says otherwise I would like to see it so I do not spread misinformation because I would hate for someone to receive bad advice that could penitently harm their engine.
Please note that code p0030 in not listed on the OP's diagnostic sheet, P0031 and P0051 are listed. I am fairly certain that this will not be a limp mode. Once the sensors are heated by the exhaust gas the heater circuit is of little use. Check with Cap Weir about this, he has posted a few times about this. The cars emissions will be higher and mileage should suffer. Short drives would not be in the best interest for the engines health but a cross country drive should be no issue.
Source: Toyota Technical Training Course. For direct link to training materials, PM me.
View attachment 59305
The only fail-safe action for O2 sensor heater circuit DTC is to shut off the heater circuit. No other fault management actions are taken. O2 sensor operation and closed loop fuel control are not suspended.
Additional Toyota-specific sources are available.
This is corroborated by direct observations and logging of ECM and sensor functions by qualified technicians. In case of heater circuit DTC, the ECM continues to use O2 sensor output to regulate fuel trims.
Different manufacturers utilize different strategies for different ECM's. Generic information sources cannot account for all variations of ECM fault management strategies. Generic information can be useful as a general guideline but cannot be relied on to diagnose or correct a specific situation with a specific ECM. To portray otherwise is wrong.
In many cases, generic information from the internet is simply wrong. As an additional example, closely related to the specific situation in this thread, the information below (same source cited by other poster, yourmechanic.com) is DEMONSTRABLY AND PATENTLY WRONG AND DOES NOT APPLY TO SPYDER ECU:
https://www.yourmechanic.com/articl...bd-ii-trouble-code-o2-sensor-circuit-malfunction-bank-1-sensor-2-by-jay-safford
If someone were to use this incorrect generic info to support a baseless claim about a downstream O2 sensor causing misfires they would be tarred and feathered and run out of town on a rail, and rightfully so. Contrary to the yourmechanic info, it is well known and agreed upon that in our ECM's the downstream O2 sensor has no effect on engine function.
This is in addition to the info about the upstream O2 sensor heater circuit from yourmechanic being wrong.
In view of this clearly wrong information, with regard to not just one but two and quite likely many more DTC's, the source cited - yourmechanic.com - and any other sources that agree with it should be regarded as suspect, and disregarded. Persons citing those sources are to be regarded as careless and misinformed, i.e. purveyors of fake technical information, and that's putting it kindly.
View attachment 59305
The only fail-safe action for O2 sensor heater circuit DTC is to shut off the heater circuit. No other fault management actions are taken. O2 sensor operation and closed loop fuel control are not suspended.
Additional Toyota-specific sources are available.
This is corroborated by direct observations and logging of ECM and sensor functions by qualified technicians. In case of heater circuit DTC, the ECM continues to use O2 sensor output to regulate fuel trims.
Different manufacturers utilize different strategies for different ECM's. Generic information sources cannot account for all variations of ECM fault management strategies. Generic information can be useful as a general guideline but cannot be relied on to diagnose or correct a specific situation with a specific ECM. To portray otherwise is wrong.
In many cases, generic information from the internet is simply wrong. As an additional example, closely related to the specific situation in this thread, the information below (same source cited by other poster, yourmechanic.com) is DEMONSTRABLY AND PATENTLY WRONG AND DOES NOT APPLY TO SPYDER ECU:
https://www.yourmechanic.com/articl...bd-ii-trouble-code-o2-sensor-circuit-malfunction-bank-1-sensor-2-by-jay-safford
If someone were to use this incorrect generic info to support a baseless claim about a downstream O2 sensor causing misfires they would be tarred and feathered and run out of town on a rail, and rightfully so. Contrary to the yourmechanic info, it is well known and agreed upon that in our ECM's the downstream O2 sensor has no effect on engine function.
This is in addition to the info about the upstream O2 sensor heater circuit from yourmechanic being wrong.
In view of this clearly wrong information, with regard to not just one but two and quite likely many more DTC's, the source cited - yourmechanic.com - and any other sources that agree with it should be regarded as suspect, and disregarded. Persons citing those sources are to be regarded as careless and misinformed, i.e. purveyors of fake technical information, and that's putting it kindly.
Hi - just an update, I ended up driving it for about 6 hours because I couldn't find any mechanics in that city with decent reviews that had any availability until next Tues or Thurs. It seems fine so far.. no strange noises, no smells, no other warning signs. Getting 27 mpg so far. What does it mean to run "rich"? I have a friend in Dallas who knows someone that is a mechanic that is going to help, once I get there. I'm in New Orleans now.
Hoping to be able to make it to Dallas tomorrow (Saturday) I'm going to go to another Autozone and see if the same error appears as someone mentioned. On a positive note, the car is really cool! As long as it makes it all the way home, I'm going to have fun with it learning how to be mechanical & stuff
When I get some downtime I'll add a picture of it on here for everyone. It has the spyder emblem on the front (instead of Toyota emblem)
Hoping to be able to make it to Dallas tomorrow (Saturday) I'm going to go to another Autozone and see if the same error appears as someone mentioned. On a positive note, the car is really cool! As long as it makes it all the way home, I'm going to have fun with it learning how to be mechanical & stuff
When I get some downtime I'll add a picture of it on here for everyone. It has the spyder emblem on the front (instead of Toyota emblem)
You just keep on going and find a mechanic who can replace those O2 sensors for you. Watch out for bad weather these cars are temperamental in the wet. Everything is gonna be just fine.
I found the relevant information that points to it in writing more specific for Toyota vehicles.
I don't fault the sources I listed because it does mention that it can vary with each manufacture but I could not find the information I was looking for in writing until Franks post pointed me to make a better search to confirm he is right.
When there is a fault in the 02 sensors heater circuit it does indeed go into fail safe mode and its action is to turn off the heater circuit only.
I don't fault the sources I listed because it does mention that it can vary with each manufacture but I could not find the information I was looking for in writing until Franks post pointed me to make a better search to confirm he is right.
When there is a fault in the 02 sensors heater circuit it does indeed go into fail safe mode and its action is to turn off the heater circuit only.
Relevant to a Camry. You should keep relevance to MR2 spyder gen III with a 1ZZ ECU. Years and models can and will be different, technology moves, forward and backward ;~D)
In Cap I trust.
In Cap I trust.
DTC fail-safe codes for a 2000 MR2 spyder shop manual are:
P0110 - intake air temp...
P0115 - Engine coolant temp...
P0120 - VTA is fixed at 0 degrees
P0325 - Max. timing retardation
P1300 - Fuel cut
Page DI-8 shop manual.
If anyone has a 2003 or later MR2 spyder shop manual that would be proof in the pudding.
P0110 - intake air temp...
P0115 - Engine coolant temp...
P0120 - VTA is fixed at 0 degrees
P0325 - Max. timing retardation
P1300 - Fuel cut
Page DI-8 shop manual.
If anyone has a 2003 or later MR2 spyder shop manual that would be proof in the pudding.
Elizabeth, keep going...you're not likely going to hurt anything. Do replace your O2 sensors as soon as practical after you get home.
A "rich" mixture means there's too much fuel in the air/fuel mixture. A "lean" mixture means there is less fuel. The optimum ratio is 14.7:1...that's 1 part fuel, 14.7 parts air.
In case you're wondering what happens on either end of the rich/lean spectrum, too lean will cause very high cylinder pressure and high combustion temps. This typically leads to melted piston heads, broken rings or other parts failing...mostly from the high pressure.
An overly rich mixture usually causes carbon to build up in the cylinder and can create "hot spots" that detonate the fuel/air charge earlier than when the spark plug fires. This generally takes much longer to build up carbon to cause damage compared to lean. So running lean can be destructive much sooner.
From the information provided in this thread, sounds like you'll be fine for awhile...but do get those codes looked into. (Don't tell MerryF, but my recommendation is to buy a couple O2 sensors and replace them yourself...around $30 each online, although you will have to splice 2 wires together on each sensor to fit the original plug. Very easy to do, and worth saving a couple hundred bucks from an auto repair shop).
A "rich" mixture means there's too much fuel in the air/fuel mixture. A "lean" mixture means there is less fuel. The optimum ratio is 14.7:1...that's 1 part fuel, 14.7 parts air.
In case you're wondering what happens on either end of the rich/lean spectrum, too lean will cause very high cylinder pressure and high combustion temps. This typically leads to melted piston heads, broken rings or other parts failing...mostly from the high pressure.
An overly rich mixture usually causes carbon to build up in the cylinder and can create "hot spots" that detonate the fuel/air charge earlier than when the spark plug fires. This generally takes much longer to build up carbon to cause damage compared to lean. So running lean can be destructive much sooner.
From the information provided in this thread, sounds like you'll be fine for awhile...but do get those codes looked into. (Don't tell MerryF, but my recommendation is to buy a couple O2 sensors and replace them yourself...around $30 each online, although you will have to splice 2 wires together on each sensor to fit the original plug. Very easy to do, and worth saving a couple hundred bucks from an auto repair shop).
It's definitely been an adventure driving this through all sorts of weather! I thought I was going to fly off the road driving in the wind in Wichita Falls, then driving in the rain was crazy as well. Now I'm in Albequerque New Mexico and have just 550 miles left to go.. new problem is I hit some potholes in a construction area and that cover thing near the exhaust is hanging down now and something is making noises, can't tell if it's coming from the engine or where it's from. I'll definitely need to take it to a mechanic here to get this checked out. So close to making it all the way!!
That's a long journey you're taking, New Orleans to Dallas!! Are you getting decent mileage during your trip? Are you moving to Texas or just going there to visit?
Made it!!
mazdaverx7 actually I drove from Orlando to Salt Lake City, haha. I stopped in New Orleans, Dallas & New Mexico.
The only reason I made this trip is because I was so picky about exactly what I wanted. The color, the leather seats, a true manual with the clutch, a 2003 or newer etc & I only could find one in Florida and for a good deal. Plus with some nice aftermarket rims & Injen cold air intake and exhaust system.
It's been quite the adventure! All the things you shouldn't drive through in this car, I can now say I've made it. I drove through a snow storm in a dark canyon last night at 2am, that was freaky. It took nearly 2 hours to drive 50 miles & I could barely see anything except snow but I made it out.
I almost hit a deer in a rainstorm, luckily it moved out of the way just in time (it ended up being about 2 feet or less from the front of the car when I passed it, after it ran off to the side) It was a large deer, would have probably crushed me in this tiny car.
So anyway back to the O2 thing. A mechanic in New Mexico looked at it and said there isn't anything obvious that's wrong and that it was safe to drive all the way back home & then have a mechanic here look at it (they said they'd have to spend some time taking everything apart to figure it out because an O2 sensor error is a common misdiagnosis & sometimes it is actually something else).
mazdaverx7 actually I drove from Orlando to Salt Lake City, haha. I stopped in New Orleans, Dallas & New Mexico.
The only reason I made this trip is because I was so picky about exactly what I wanted. The color, the leather seats, a true manual with the clutch, a 2003 or newer etc & I only could find one in Florida and for a good deal. Plus with some nice aftermarket rims & Injen cold air intake and exhaust system.
It's been quite the adventure! All the things you shouldn't drive through in this car, I can now say I've made it. I drove through a snow storm in a dark canyon last night at 2am, that was freaky. It took nearly 2 hours to drive 50 miles & I could barely see anything except snow but I made it out.
I almost hit a deer in a rainstorm, luckily it moved out of the way just in time (it ended up being about 2 feet or less from the front of the car when I passed it, after it ran off to the side) It was a large deer, would have probably crushed me in this tiny car.
So anyway back to the O2 thing. A mechanic in New Mexico looked at it and said there isn't anything obvious that's wrong and that it was safe to drive all the way back home & then have a mechanic here look at it (they said they'd have to spend some time taking everything apart to figure it out because an O2 sensor error is a common misdiagnosis & sometimes it is actually something else).
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
