cosmic.artifact
Virginia
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Joined: 02/13/2009
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I have a bit of experience with these oxy sensor codes, First thing I would do is buy you a can of gum-cutter and try spraying the (intake manifold) upper and lower, do a runner/cylinder at a time, and then listen for rpm changes, that will let you know if it is an intake manifold leak. It is a possibility... because your plenum is made of ABS plastic most likely and GM has that problem often. (dont go hawk wild with the gum cutter it will ignite) use the small straw supplied with the can.
These are very common emissions failure codes, I have found most of the time and depending on mileage that it IS usually the oxy sensors that go bad, I seem to replace them on a daily basis.
Another thing most folks do not realize is that oxy sensors are serviceable items just like a spark plug in a sense that they wear out. We usually call it SLOW from switching back and forth rich to lean. An oxygen sensor looks similar to a plug but in now way functions the same, I use that explanation often to customers and it makes it easier to understand that they do not last the life of the vehicle... 1998 humm, yeah its prolly about time specially if the engine seems to be running ok to you.
good luck...
* This post was
edited 03/10/09 08:21pm by cosmic.artifact *
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enblethen
Moses Lake, WA USA
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Joined: 01/05/2005
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Good Sam RV Club
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After the engine warms up, the fuel being dumped in by the fuel regulator can burn off. The code has already set.
I doubt whether both primary oxygen sensors would fail at the same time. The engine is getting too much raw fuel and it is affecting the oxygen sensors.
Bud
Suzuki XL7 pushing Pace Arrow
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cosmic.artifact
Virginia
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Sounds quite logical, although after warm-up the oxy sensors tell the ECM how much fuel to regulate and would light both codes as it is a sequential injected engine.
emission codes can be very difficult online HA ! could be a mass air flow sensor too as these seem to get replaced quite often on GM, but the last fuel pressure regulator I can recall doing was on a 4.3 vortec somewhere in the lower/mid 90's model.
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cosmic.artifact
Virginia
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Keep in mind... if you are dumping too much fuel in 'open loop' you can usually smell the raw fuel if you have a nose for it. If the codes have a hard-on (we like to call it) meaning... come back on right after you clear the codes and not in 'closed loop' yet, it quite possibly is a Mass Air Flow meter or Fuel Pressure Regulator.
I think GM did away with the 'spider' type regulator/injectors in the mid 90's for this very reason.
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edited 03/10/09 09:39pm by cosmic.artifact *
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cosmic.artifact
Virginia
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Q: What is the difference between 'Open Loop' and 'Closed Loop'?
A: When the engine is first started, and rpm is above 400 rpm, the system goes into 'Open Loop' operation. In 'Open Loop', the ECM will ignore the signal from the Oxygen (O2) sensor and calculate the air/fuel ratio based on inputs from the Coolant Tempature Sensor and Mass Air Flow sensor, but mostly from a pre-programmed table in the ECM.
The system will stay in 'Open Loop' until the following conditions are met:
1. The O2 sensor has varying voltage output, showing that it is hot enough to operate properly. (This depends on temperature)
2. The coolant sensor is above a specified temperature about 40oC/104oF.
3. A specific amount of time has elapsed after starting the engine.
The specific values for the above conditions vary with different engines and are stored in the mem-cal. When these conditions are met, the system goes into 'Closed Loop' operation. In 'Closed Loop', the ECM will calculate the air/fuel ratio (injector on-time) based on the various sensors but mainly the O2 sensor. This allows the air/fuel ratio to stay very close to 14.7:1.
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in open loop the ECM ignores the readings from the oxy sensors.
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smithrock
Long Beach, CA.
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Joined: 01/07/2005
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I was having this problem awhile ago, and it would idle real rough and I could smell unburned fuel. And I was getting various codes like multi-cylinder misfire along with the 02 codes. I put new sparkplugs in, and new TPS, cleaned the EGR valve and put in new 02 sensors in bank 1 sensors 1 & 2 and 1 sensor in bank 2 sensor 1. Seemed to run just fine until about a month ago, and I was getting code P0161 which is bank 2 sensor 2 (the on ly one i didn't change) Yesterday is when I got those others codes. Truck still seems to be running fine. I had my air/fuel ratio checked it's at 14.7
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cosmic.artifact
Virginia
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try an ECT (engine coolant temp sensor) seems like your doing the trial and error fix-er yourself approach and this is a pretty inexpensive item to replace.
I have been replacing these alot in tune-ups that I do as a preventive maintenance because of the low price of the sensor overall.
the DEQ's CRT class is one of the hardest I have to re-certify for every 3 yrs, sounds like it could be a simple fix and I can not tell you how much they stress replacing this component for emissions failures in class. I notice also your on Cali emissions standards (which are going to be much tighter than any state) therefore much more touchy to readings in open loop.
One thing I surely will not buy searching for an RV or any other vehicle is one that was manufactured for sale in the state of California, specially an rv or a truck... the engines have slight variances and different sensors, your O2's are not actually like our O2 sensors, yours are called 'Air/Fuel Metering' sensors and they do function differently.
If you are trying to subvert emissions tests, just go grab you a PO# box in a county that has no testing and register your vehicle to the po box (which I think is $13 a year) people do that here all the time as a lot of counties just outside D.C. do not have testing for emissions.
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smithrock
Long Beach, CA.
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Do you have a pic of an ECT or a link where I can see one for my vehicle?
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cosmic.artifact
Virginia
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REMOVAL PROCEDURE...
*CAUTION : Take care when handling the coolant sensor. Damage to the coolant sensor affects the proper operation of the fuel control system.
1. Relieve the coolant pressure.
2. Disconnect the negative battery cable.
3. Drain the cooling system below the level of the sensor.
4. Disconnect the electrical connector releasing locking tab.
5. Remove the coolant sensor from engine.
(item #2)
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smithrock
Long Beach, CA.
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Thanks! I'll try and work on it tomorrow. Can I clean the ECT? Or do I need to buy a new one? Can I purchase from Autozone or Kragens?
Question: What does an ECT have to do with 02 codes?
I'm only asking because I don't know.
thanks
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