O2 codes

[caddypete]

I replaced my rear bank O2 sensor because I would get codes that realated to them, I still get these codes what do I look for next? besides a honest dealership? I used a ACDelco sensor, checked for intake leaks changed fuel filter and air filter. I know the rear bank is not lean the plugs are black sooty unlike the front bank but something is telling the computer to richen the rear bank, the only thing I can think of is there is a exhaust leak before the sensor, I can't see or hear one. ANY IDEAS? The computer richens that bank soo much that there are times after starting the car it will miss until you give it a romp on the pedal,then it will clear up with a cloud out the exhaust

P0131 - Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 1 Sensor 1

P0132 - Heated Oxygen Sensor (HO2S) Circuit High Voltage Bank 1 Sensor 1

P0171 - Fuel Trim System Lean Bank 1

[Ranger]

Leaky FPR?

[BodybyFisher]

From what I can see you have been complaining about this lean condition since October 2005. If I were you I would change your intake manifold gaskets or at the very least pull the intake manifold and check the gaskets for damage and look for intake manifold cracks, etc.

DTC P0171 Fuel Trim System Lean Bank 1

Circuit Description

The PCM controls a closed loop air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. The PCM monitors the heated oxygen sensor signal voltage and adjusts the fuel delivery based on the signal voltage while in closed loop. A change made to the fuel delivery changes the Long and Short Term Fuel Trim values. The Short Term Fuel Trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine fueling. The Long Term Fuel Trim values change in response to trends in Short Term Fuel Trim. The Long Term Fuel Trim makes coarse adjustments to fueling in order to re-center and restore control to Short Term Fuel Trim. You can use a scan tool in order to monitor the Short and Long Term Fuel Trim. The ideal fuel trim values are around 0 percent. A positive Fuel Trim value indicates that the PCM is adding fuel in order to compensate for a lean condition. A negative Fuel Trim value indicates that the PCM is reducing the amount of fuel in order to compensate for a rich condition. If the PCM detects an excessively Rich or Lean condition, the PCM sets a DTC. The long term fuel trim diagnostic parameter is an average of several of the long term speed load learn cells which the PCM selects based on the engine speed and the engine load.

Conditions for Running the DTC

No TP sensor, MAP sensor, MAF sensor, HO2S, KS sensor, Idle speed, Injector, Misfire, EGR Flow, CMP sensor DTCs are set.

EGR Flow test is inactive.

Engine coolant temperature between 20°C (68°F) and 115°C (239°F).

Barometric pressure more than 75 kPa.

Mass air flow between 3-60 grams per second.

Manifold absolute pressure between 15-85 kPa.

Intake air temperature between -20°C (-4°F) and 100°C (212°F).

Engine speed between 500-4000 RPM.

Throttle angle less than 65 percent.

Vehicle speed less than 131 km/h (82 mph).

Conditions for Setting the DTC

The PCM in not able to correct for a lean condition in cylinder bank 1.

Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic has been run and failed.

The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Conditions for Clearing the MIL/DTC

The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.

The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

The DTC can be cleared by using the scan tool Clear DTC Information function.

Visually/physically inspect the following items:

Vacuum hoses for splits, kinks and proper connections.

Throttle body, intake manifold and EGR valve for vacuum leaks.

Crankcase ventilation valve and/or system for leaks including a loose or missing Oil Fill cap or oil dipstick.

Contaminated fuel, refer to Alcohol/Contaminants-in-Fuel Diagnosis .

PCM and sensor grounds are clean tight and in proper locations.

MAF sensor inlet screen for damage, or a restriction.

Air induction system after MAF sensor for vacuum leaks.

Engine mechanical failure.

If a condition is found, repair as necessary

Visually/physically inspect the following items:

Bank 1 exhaust leaks, missing or loose exhaust hardware.

HO2S bank 1 sensor 1 is installed securely and electrical connector not contacting exhaust system.

Engine mechanical failure.

Vacuum leaks that will only affect bank 1 (Intake manifold, injector O-rings, etc.)

If a condition is found, repair as necessary

[caddypete]

Thanks. I just realized my old age is really starting to show. Why do I always want to blame the sensors, and not what they are saying? But I read plugs and I see a rich condition and disagree with the sensor. I just got get the carburated.2 valve to a cylinder,points and condenser ignition ingrained thinking out of my head.And start listening to what the computer says. By the way I turned 51, 50 minutes ago

[BodybyFisher]

Happy Birthday, mine is on the 7th of July (I have a few years on you)! I was hoping what I posted would help to explain the logic behind the symptoms you were getting..

The PCM in your case is richening up the mixture as much as it can. That is why you are getting black plugs. But unfortunately it can not richen up the mixture enough. You must have a large vacuum leak.. Are all four plugs on Bank 1 black or just some of them?

Was your starter ever replaced? As you know that entails removing the intake manifold. You might start by re-torqing the intake and looking for vacuum leaks that would ONLY impact Bank 1. Unfortunately besides the intake manifold gaskets I don't know what kind of a vacuum leak would impact only Bank 1, maybe a crack..

To cut to the chase, I would buy new intake manifold gaskets and just replace them. Watch your torque its in inch pounds not foot pounds (I once made that mistake). Let me know if I can help.

If you understood the points, carb type systems these systems are very logical, see these articles for more background:

http://www.autotap.com/Articles/Understand...en_Sensors.html

http://www.autotap.com/Articles/Replacing_...aintenance.html

[BodybyFisher]

[uGH, double post, this can be deleted]

[caddypete]

Nope starter hasn't been replaced. I will replace the intake gasket. It is only the rear bank that runs rich. I have checked all the connections on the intake, but figured if there was a leak it would cause a lean code on both banks. Which also confuses me what sensor is reading a lean condition? If the O2 sensor is the one reading the air fuel ratio and sensing a lean condition, I have a hard time comprehending it getting that reading because it is also black sooty like a rich plug. My thinking was even if that bank was running correct and I had a exhaust leak that drew in air the sensor could read lean and correct it but when the sensor looks like a rich condition plug would, how does it read lean when it is covered in half burnt fuel?

[BodybyFisher]

Nope starter hasn't been replaced. I will replace the intake gasket. It is only the rear bank that runs rich. I have checked all the connections on the intake, but figured if there was a leak it would cause a lean code on both banks. Which also confuses me what sensor is reading a lean condition? If the O2 sensor is the one reading the air fuel ratio and sensing a lean condition, I have a hard time comprehending it getting that reading because it is also black sooty like a rich plug. My thinking was even if that bank was running correct and I had a exhaust leak that drew in air the sensor could read lean and correct it but when the sensor looks like a rich condition plug would, how does it read lean when it is covered in half burnt fuel?

Its reading heat, the lean mixture is causing a temperature that appears to be lean and the PCM has continued to richen the mixture to solve the problem and it ran out of the ability to compensate. If I am wrong on this thinking, maybe someone will chime in on this. GM has had some problems with their intake manifold gaskets, the 3100 and 3400's have intake manifold gasket problems, not that that means a hell of a lot here, because the failure was related to the cooling system, but they CAN go bad or be damaged or loose.. You have been complaining about this for a long time. Try torqing it down first, you might be sucking air someplace. Do you have the torque specs?

[caddypete]

I thought I would post back because most post thier problems but not what the outcome was which doesn't help others. I went to check on what other things that may be needed while replacing my intake gasket and run a unlit propane torch around the intake area to see if I could locate a leak. I decided to check my pcv valve because it was right in front of my face. When I went to pull the rubber hose to the valve I noticed the whole underside of the hose was ripped. I replaced it with a piece of gas line and added that to my things to be ordered. Well it's been almost a week and no O2 codes. Not only that my mpg have increased by 1.6 mpg. Just waiting to see if that was the cause my problem,

[BodybyFisher]

I thought I would post back because most post thier problems but not what the outcome was which doesn't help others. I went to check on what other things that may be needed while replacing my intake gasket and run a unlit propane torch around the intake area to see if I could locate a leak. I decided to check my pcv valve because it was right in front of my face. When I went to pull the rubber hose to the valve I noticed the whole underside of the hose was ripped. I replaced it with a piece of gas line and added that to my things to be ordered. Well it's been almost a week and no O2 codes. Not only that my mpg have increased by 1.6 mpg. Just waiting to see if that was the cause my problem,

Yes a vacuum leak at the PCV will cause that, you are allowing more oxygen into your intake. Good find! Mike