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2005 gmc envoy_slt
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Discussion Starter · #1 ·
Hello
I have been looking for awhile but have not found a thread questioning P0054 code. I have a 2005 GMC Envoy 4.2 L XLT 4WD ~ 88k miles. I started having issues with it when I started doing maintenance on the Oxygen sensors I replace both at 83K. Around the 86K mark I got the p0410 issue. Fooled around with it for about a month when I finally found out it was the solenoid valve. After replacing it I still had the problem and finally gave it to the dealer to trouble shoot it (by the way the valve was bad). The dealer charged $100 to hook up the scan tool and told me it was either the wiring to the Oxygen sensor 2 or the PCM. They wanted another $100 to check the wiring. I declined the service since I knew it would only take me 15 min to check the wiring myself. In the process of going home I picked up another Oxygen sensor. After getting home I check the out the wires and they all checked okay and I installed the new Oxygen sensor at the same time (either the bad solenoid burned out the previous new sensor or I was sold a bad sensor don't know). I cleared all the codes and had no trouble until now.

I now get a p0054 error pointing me back to the Oxygen sensor. Tomorrow I will be checking the wires again. Yesterday I installed a new sensor again (3rd one) and it had no impact. (is this sensor bad? I don't know) Does any body know a way to bench check the sensor to see if it is bad? I don't own a tech II scan tool since they cost a few thousand dollars. Is there an alternate means to setting the Oxygen sensor circuit to on like the scan tool does to do correct trouble shooting? I use to be a mechanic 35 + years ago in those days there was no such thing or concern for environment. I always found alternative means to do things with out test equipment when helping people on the road side and minimal tools.

Anybody have any Ideas what may be the problem. I find it hard to believe it to be the PCM. This vehicle is still a puppy compared to others I had.
 

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2004 gmc
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Heated O2 sensors have a resistive heater between two pins that draws around 600mA of 12V straight from fuse 29 under the hood. On my 2004 schematic, they use pink wire for the 12V on both sensors, and sensor 1 low side is d-gn, and sensor 2 low side is bk/wh. Both the low side controls go to the PCM, and ground when the sensor is to be heated.

The other two pins are the sensor output, varying from 10-1000mV in the presence of Oxygen. It's a differential signal going to the PCM for measurement, so you can use the meter floating differentially across the wires on a low voltage range for sensitivity. Sensor 1 uses TN and PU/WH wires, and sensor 2 uses tn/wh and pu/wh.

I don't see any connection between the exhaust manifold solenoid valve and O2 sensor wiring.

For theory of operation: http://en.wikipedia.org/wiki/Oxygen_sensor

For just over the $100 per trip you're wasting at the dealer, you can buy a hand held code scanner at any parts store.

 

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2005 gmc envoy_slt
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Discussion Starter · #3 ·
Thanks for the input and it is welcomed. I have a code reader unfortunately all it does is read the code and clear them. The dealer was my last resort not believing the new O2 sensor was bad. Believe me I don’t like going to auto shops it seems they don’t always know what is going on either. I have a sneaky suspicion that it may be bad O2 sensor again. I have been getting them at Auto Zone and have had no problem returning them. I am just looking for a sure way to know if it is a bad O2 sensor before asking for my money back and going to another parts store. I will be checking my wires again tomorrow but don’t expect to find a problem. That only leaves me with two things the sensor or the PCM. I can only say ouch if it is the PCM. :thx
 

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How are you checking the wiring? Ohming it out all the way back to the PCM? The connector on the PCM end could have oxidized slightly and just need reseating.

You can make sure the sensor is good by checking the heater current, and then checking the output voltage while it's running. The typical closed loop operation will have the sensor outputting around 1/2 V.

When the dealer had their scan tool hooked up to check the code, it's only about 15 seconds work to ask it to measure the heater current and sensor output voltage, the raw data of both of them is constantly measured by the PCM. $100 extra INDEED. :hissy: :no: :crazy:
 

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Discussion Starter · #5 ·
I did the check two different ways. I started with an analog ohm meter ran a wire from the PCM to the O2 connector got low resistance. Also check it by grounding the wire at the PCM connector an reading he O2 connector to ground with a DMM to measure the resistance. I found running a wire from the PCM to the O2 connector to be more precise since I could determine the ohm reading of the wire run and subtract it from my reading to get a more precise reading. Got less than 1 ohm well below the 3 ohm specifications. The DMM is the route to go as is running wire from one end to the other.

The PCM connector three pins 18,26,31 where checked back to the O2 connector. Also did the same for the fuse wire. All wires checked out. I also cross checked all the wires for any shorts or bleeding to another wire got open readings for all. Reconnected the connector at the PCM and turned on the ignition switch and checked for power at the O2 connector with a test light and got a solid light. Since I cannot command the O2 on I could not check for the blinking of the source.

I did an Ohm reading of the O2 sensor and only get reading across the heater the other two wires give open signals. I check all four wires for readings to the sensor's body and got open signals. I don't know what the reading are suppose to be. My OEM sensor showed 3 Ohms across the heater the new one 13 Ohms.

While I was doing all this work I had disconnected the negative side of the battery so the code was cleared. I had some errands to run and on my way back home the light came back on. At this point I am pretty sure the PCM is hosed. While I had the C2 connector off at the PCM I checked to make sure no pins were pushed back and that they were all clean. The seal around the connector looked like it was doing its job. I also checked the pins at the O2 connectors.
:mad:
 

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2003 chevy trailblazer_ls
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Hello
Does any body know a way to bench check the sensor to see if it is bad?
Ask and ye shall recieve:
Oxygen Sensor Information

What will damage my O2 sensor?
Home or professional auto repairs that have used silicone gasket sealer that is not specifically labeled "Oxygen sensor safe", "Sensor safe", or something similar, if used in an area that is connected to the crankcase. This includes valve covers, oil pan, or nearly any other gasket or seal that controls engine oil. Leaded fuel will ruin the O2 sensor in a short time. If a car is running rich over a long period, the sensor may become plugged up or even destroyed. Just shorting out the sensor output wire will not usually hurt the sensor. This simply grounds the output voltage to zero. Once the wiring is repaired, the circuit operates normally. Undercoating, antifreeze or oil on the *outside* surface of the sensor can kill it. See how does an Oxygen sensor work.
Will testing the O2 sensor hurt it?
Almost always, the answer is no. You must be careful to not *apply* voltage to the sensor, but measuring it's output voltage is not harmful. As noted by other posters, a cheap voltmeter will not be accurate, but will cause no damage. This is *not* true if you try to measure the resistance of the sensor. Resistance measurements send voltage into a circuit and check the amount returning.
How does an O2 sensor work?
An Oxygen sensor is a chemical generator. It is constantly making a comparison between the Oxygen inside the exhaust manifold and air outside the engine. If this comparison shows little or no Oxygen in the exhaust manifold, a voltage is generated. The output of the sensor is usually between 0 and 1.1 volts. All spark combustion engines need the proper air fuel ratio to operate correctly. For gasoline this is 14.7 parts of air to one part of fuel. When the engine has more fuel than needed, all available Oxygen is consumed in the cylinder and gasses leaving through the exhaust contain almost no Oxygen. This sends out a voltage greater than 0.45 volts. If the engine is running lean, all fuel is burned, and the extra Oxygen leaves the cylinder and flows into the exhaust. In this case, the sensor voltage goes lower than 0.45 volts. Usually the output range seen seen is 0.2 to 0.7 volts. The sensor does not begin to generate it's full output until it reaches about 600 degrees F. Prior to this time the sensor is not conductive. It is as if the circuit between the sensor and computer is not complete. The mid point is about 0.45 volts. This is neither rich nor lean. A fully warm O2 sensor *will not spend any time at 0.45 volts*. In many cars, the computer sends out a bias voltage of 0.45 through the O2 sensor wire. If the sensor is not warm, or if the circuit is not complete, the computer picks up a steady 0.45 volts. Since the computer knows this is an "illegal" value, it judges the sensor to not be ready. It remains in open loop operation, and uses all sensors except the O2 to determine fuel delivery. Any time an engine is operated in open loop, it runs somewhat rich and makes more exhaust emissions. This translates into lost power, poor fuel economy and air pollution. The O2 sensor is constantly in a state of transition between high and low voltage. Manfucturers call this crossing of the 0.45 volt mark O2 cross counts. The higher the number of O2 cross counts, the better the sensor and other parts of the computer control system are working. It is important to remember that the O2 sensor is comparing the amount of Oxygen inside and outside the engine. If the outside of the sensor should become blocked, or coated with oil, sound insulation, undercoating or antifreeze, (among other things), this comparison is not possible.
How can I test my O2 sensor?
They can be tested both in the car and out. If you have a high impedence volt meter, the procedure is fairly simple. It will help you to have some background on the way the sensor does it's job. Read how does an O2 sensor work first.
Testing O2 sensors that are installed
The engine must first be fully warm. If you have a defective thermostat, this test may not be possible due to a minimum temperature required for closed loop operation. Attach the positive lead of a high impedence DC voltmeter to the Oxygen sensor output wire. This wire should remain attached to the computer. You will have to back probe the connection or use a jumper wire to get access. The negative lead should be attached to a good clean ground on the engine block or accessory bracket. Cheap voltmeters will not give accurate results because they load down the circuit and absorb the voltage that they are attempting to measure. A acceptable value is 1,000,000 ohms/volt or more on the DC voltage. Most (if not all) digital voltmeters meet this need. Few (if any) non-powered analog (needle style) voltmeters do. Check the specs for your meter to find out. Set your meter to look for 1 volt DC. Many late model cars use a heated O2 sensor. These have either two or three wires instead of one. Heated sensors will have 12 volts on one lead, ground on the other, and the sensor signal on the third. If you have two or three wires, use a 15 or higher volt scale on the meter until you know which is the sensor output wire. When you turn the key on, do not start the engine. You should see a change in voltage on the meter in most late model cars. If not, check your connections. Next, check your leads to make sure you won't wrap up any wires in the belts, etc. then start the engine. You should run the engine above 2000 rpm for two minutes to warm the O2 sensor and try to get into closed loop. Closed loop operation is indicated by the sensor showing several cross counts per second. It may help to rev the engine between idle and about 3000 rpm several times. The computer recognizes the sensor as hot and active once there are several cross counts. You are looking for voltage to go above and below 0.45 volts. If you see less than 0.2 and more than 0.7 volts and the value changes rapidly, you are through, your sensor is good. If not, is it steady high (> 0.45) near 0.45 or steady low (< 0.45). If the voltage is near the middle, you may not be hot yet. Run the engine above 2000 rpm again. If the reading is steady low, add richness by partially closing the choke or adding some propane through the air intake. Be very careful if you work with any extra gasoline, you can easily be burned or have an explosion. If the voltage now rises above 0.7 to 0.9, and you can change it at will by changing the extra fuel, the O2 sensor is usually good. If the voltage is steady high, create a vacuum leak. Try pulling the PCV valve out of it's hose and letting air enter. You can also use the power brake vacuum supply hose. If this drives the voltage to 0.2 to 0.3 or less and you can control it at will by opening and closing the vacuum leak, the sensor is usually good. If you are not able to make a change either way, stop the engine, unhook the sensor wire from the computer harness, and reattach your voltmeter to the sensor output wire. Repeat the rich and lean steps. If you can't get the sensor voltage to change, and you have a good sensor and ground connection, try heating it once more. Repeat the rich and lean steps. If still no voltage or fixed voltage, you have a bad sensor. If you are not getting a voltage and the car has been running rich lately, the sensor may be carbon fouled. It is sometimes possible to clean a sensor in the car. Do this by unplugging the sensor harness, warming up the engine, and creating a lean condition at about 2000 rpm for 1 or 2 minutes. Create a big enough vacuum leak so that the engine begins to slow down. The extra heat will clean it off if possible. If not, it was dead anyway, no loss. In either case, fix the cause of the rich mixture and retest. If you don't, the new sensor will fail.
Testing O2 sensors on the workbench.
Use a high impedence DC voltmeter as above. Clamp the sensor in a vice, or use a plier or vice-grip to hold it. Clamp your negative voltmeter lead to the case, and the positive to the output wire. Use a propane torch set to high and the inner blue flame tip to heat the fluted or perforated area of the sensor. You should see a DC voltage of at least 0.6 within 20 seconds. If not, most likely cause is open circuit internally or lead fouling. If OK so far, remove from flame. You should see a drop to under 0.1 volt within 4 seconds. If not likely silicone fouled. If still OK, heat for two full minutes and watch for drops in voltage. Sometimes, the internal connections will open up under heat. This is the same a loose wire and is a failure. If the sensor is OK at this point, and will switch from high to low quickly as you move the flame, the sensor is good. Bear in mind that good or bad is relative, with port fuel injection needing faster information than carbureted systems. ANY O2 sensor that will generate 0.9 volts or more when heated, show 0.1 volts or less within one second of flame removal, AND pass the two minute heat test is good regardless of age. When replacing a sensor, don't miss the opportunity to use the test above on the replacement. This will calibrate your evaluation skills and save you money in the future. There is almost always *no* benefit in replacing an oxygen sensor that will pass the test in the first line of this paragraph.
 

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I had the same code pop up after replacing the O2 sensor (downstream). I started out with the P0410 code, looked at that forum and trouble shot and found that the check valve needed replaced, the haynes manual said the code was for the downstream O2 sensor, so while I was at it I replaced it. Cleared that code and received the P0054 code the next day. Checked the connections and couldn't see anything wrong. Took it to the dealer for further diagnostics and was told that some of the aftermarket O2 sensors are causing this code. They are ordering a new O2 sensor in to try that, if that doesn't work I was told we are looking at the PCM. I will let you know if the OEM O2 sensor solves the problem
 

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2002 chevy trailblazer_lt
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Thanks for the input and it is welcomed. I have a code reader unfortunately all it does is read the code and clear them. The dealer was my last resort not believing the new O2 sensor was bad. Believe me I don’t like going to auto shops it seems they don’t always know what is going on either. I have a sneaky suspicion that it may be bad O2 sensor again. I have been getting them at Auto Zone and have had no problem returning them. I am just looking for a sure way to know if it is a bad O2 sensor before asking for my money back and going to another parts store. I will be checking my wires again tomorrow but don’t expect to find a problem. That only leaves me with two things the sensor or the PCM. I can only say ouch if it is the PCM. :thx
Just a quick question, What O2 sensors are you using if it's Bosch they seem to not work to well in our TV's. I'd recommend AC Delco! From what i've seen Bosch and Denso are the only ones Autozone carry. Advaced Auto Parts has the AC Delco ones, i'll tell ya you do pay for them seeing as they are $97 here. You may try Rockauto or Gmpartsdirect or something like that for the OEM AC's that are cheaper. You may have to wait longer to get them but if it saves you money then go for it. Hope i was of some help here :thumbsup:
 

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2002 chevy trailblazer_lt
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Just a quick question, What O2 sensors are you using if it's Bosch they seem to not work to well in our TV's. I'd recommend AC Delco! From what i've seen Bosch and Denso are the only ones Autozone carry. Advaced Auto Parts has the AC Delco ones, i'll tell ya you do pay for them seeing as they are $97 here. You may try Rockauto or Gmpartsdirect or something like that for the OEM AC's that are cheaper. You may have to wait longer to get them but if it saves you money then go for it. Hope i was of some help here :thumbsup:
I'll get ya a link and part number in a few gotta go look at mine to get part number, but come to think of it what year is your TV? It'd be nice if you fill out your info please. Ok just looked on Rockauto.com and they have both the upstream one (exhaust man) 73.00 and the downstream one 40.00! Just need your year and i can get an exact fit for yours.
 

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Every enthusiast owner (which is pretty much all the members of this site ...) should own a proper scan tool, not just a code reader. There is a LOT you can diagnose with even the cheapest scan tool that has a live-readout facility, and for the price of one oxygen sensor, you could have had a scan tool and found out FOR SURE if the sensors are bad or not.

There are a lot of threads in here on oxygen sensors; how to remove them, how to install them and how to read them in a scan tool. I have written up a guideline for readings several times over. The threads are out there to see. (Check in particular members who are having mileage or MPG issues.)

Throwing parts at a problem is not the way to do things. With all the wonderful people in this forum, some basic tools and the ability to do some minimal searching, one can always find the easiest, cheapest and most common solutions first before they start just replacing parts.

We have also noticed two other issues that seem to crop up over and over in this forum: the need to regularly clean the throttle body (which is the cause of a LOT of seemingly unrelated problems if not done regularly) and a strange feeling that "aftermarket parts are BETTER than OEM; they just HAVE to be."

This second view may be true on things like shocks, but AC Delco still makes some of the best brake pads and brake rotors for our vehicles, the best oxygen sensors, top rated air and oil filters and most especially, the ONLY spark plugs that we should be putting in.

We can't solve every problem out there, and we can't diagnose someone's vehicle without a lot of background information but the people in here are GREAT for helping owners who are also prepared to help themselves to an extent. Not everyone is a top wrench of course, but owning a scan tool and being a member of this forum will go a LONG way.

Good luck, and let us know how things are working out for you!
 

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I had the same code pop up after replacing the O2 sensor (downstream). I started out with the P0410 code, looked at that forum and trouble shot and found that the check valve needed replaced, the haynes manual said the code was for the downstream O2 sensor, so while I was at it I replaced it. Cleared that code and received the P0054 code the next day. Checked the connections and couldn't see anything wrong. Took it to the dealer for further diagnostics and was told that some of the aftermarket O2 sensors are causing this code. They are ordering a new O2 sensor in to try that, if that doesn't work I was told we are looking at the PCM. I will let you know if the OEM O2 sensor solves the problem
Please keep us posted, I'm having the same P0054 code after replacing both O2 sensors from Auto Zone. Does it appear to be the downstream sensor malfunctioning?
 

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Please keep us posted, I'm having the same P0054 code after replacing both O2 sensors from Auto Zone. Does it appear to be the downstream sensor malfunctioning?
Just wanted to add, that I replaced the downstream sensor with AC Delco from Rock Auto, and it fixed the P0054 code. Auto Zone was very good about taking the defective Bosch O2 sensor back.
 
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