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KingKota2001
Dodge Dakota
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6/02/2005
05:14:38
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 Subject: Oxygen Sensors
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Been doing a lot of searching on oxgen sensors because my check engine light just came on at 49,000 miles and it's throwing p0141 AND p0161 codes. I can understand one O2 sensor going bad, but two at the same time? Could something have gotten them contaminated, like a bad PCV or a bad batch of fuel? I reset the computer and cleared the light for a hundred miles or so, but it came on again. I'll give it one more tank of (different)fuel & a reset, then have Autozone do one of their code checks. Thanks for any feedback.
2001 CC 4.7 Auto
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?
Dodge Dakota
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6/02/2005
08:45:00
| RE: Oxygen Sensors
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P0161 HO2S Heater Circuit Bank 2 Sensor 2
P0141 HO2S Heater Circuit Bank 1 Sensor 2
These codes ( as above ) mean fault with
the heater circuit to the sensors
= possible fuse problem
otherwise probable wiring problem
' sensor 2 ' should be behind cat
Were you off-road , or in some other way
caught wiring under truck ?
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KingKota2001
Dodge Dakota
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6/02/2005
11:00:15
| RE: Oxygen Sensors
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The only stress the truck has seen recently was towing a 1k trailer across town. It was a U-Haul trailer with a very knarly-looking flat connector, so that fuse idea is worth checking out. I might just pull that back sensor and have a look at it too just for the heck of it. I'm praying that it's not a PCM problem. Thanks for the input.
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Bob Lincoln
Dodge Dakota
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6/02/2005
14:13:38
| RE: Oxygen Sensors
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Intermittent or bad ground or harness connection.
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dickc
Dodge Dakota
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6/02/2005
21:45:22
| RE: Oxygen Sensors
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Those two O2 sensors are powered by the same relay. The relay is located in the Power Distribution Center under the hood. The relays all have the same part number so maybe you can swap with another one for troubleshooting.
Good luck
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KingKota2001
Dodge Dakota
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6/03/2005
03:53:49
| RE: Oxygen Sensors
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In what way do those sensors/heater circuits affect performance? I've read on other threads about O2 sensors wreaking havoc with idle, power, etc., but when the engine MIL came on it didn't seem to affect a thing. I wasn't able to check emmissions right there and then, but driveability didn't seem affected at all.
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Dan M
Dodge Dakota
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6/03/2005
06:32:40
| RE: Oxygen Sensors
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the o2 sensors check the air/fuel ratio and sends input back to pcm. In an ideal situation you alternating between rich and lean conditions which averages out to neither rich nor lean.
have you checked you gas milage?
running rich will cause the cat to go bad.
and as far as performance goes, you've got the obvious affects of either running lean (too much air and not enough fuel) or rich (too much fuel and not enough air).
- Dan M
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dickc
Dodge Dakota
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6/03/2005
08:49:11
| RE: Oxygen Sensors
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The "Heater" Circuit is separate from the "Operational" Circuit. O2 Sensors operate at a high temperature and heating them allows an earlier closed loop. If the engine is at normal operating temperature there probably won't be a noticeable difference in performance. Until the O2 Sensors heat up the VCM will not be able to use their input for fuel scheduling.
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KingKota2001
Dodge Dakota
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6/03/2005
09:22:30
| RE: Oxygen Sensors
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A curious thing about the engine MIL coming on is the time between illuminations. It's come on twice...and after I reset it the first time it took about a week ( 3 trips of about 20 miles or so ) to light again. If the heater circuits are bad enough to throw a code, why did it take so long to light the second time ( yesterday )? Seems it would have gotten to operating temperature at least a couple of times in the time between illuminations to go into closed loop.
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dickc
Dodge Dakota
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6/04/2005
03:07:56
| RE: Oxygen Sensors
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I also have an '01 CC 4.7. The first time The MIL light came on for the O2 Heater Circuit I just turned off the light. About a week later the code set again. I turned off the light but it came right back on again. You will probably get a hard fail soon. My problem was an "open" heater circuit in the 2-2 O2 Sensor.
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KingKota2001
Dodge Dakota
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6/04/2005
20:43:43
| RE: Oxygen Sensors
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Since I got the codes for BOTH downstream heaters, I'm kind of assuming the problem is not the sensors. But stranger things have happened. Any idea where the fuse is that protects those circuits? That option seems unlikely, given that the light hasn't come back on for a few days/trips/miles, and nothing else that I know of seems affected. When (or if) it comes back I'll hopefully have some time to do some serious troubleshooting.
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Mopar8
Dodge Dakota
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6/05/2005
14:09:14
| RE: Oxygen Sensors
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This seems to be a trend , my 2001 SLT just started this same trick at 45000 , thinking it was the sensor only I got a new one and disconnected the old one, Advance auto sent the wrong one so I reconnected the old one and the light stayed off for a week then reset the code, Gonna do some circuit testing and will get back if I find any thing that will help us all out
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Branson
Dodge Dakota
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6/05/2005
14:36:25
| RE: Oxygen Sensors
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The O2 sensor heater merely gets the sensor to the right monitoring temperature much quicker than the passing exhaust gas will, so the engine can more quickly go into closed loop mode for emissions purposes.
With no heater (like the early model sensors), the sensor will eventually work as designed, it'll just take longer to get to temperature.
Meanwhile you still have a MIL for heater circuit that either won't go away or keeps coming back.
Upstream sensors modify the air/fuel mixture, based on oxygen content of the exhaust gases.
Downstream sensors check that the catalytic converter is doing its job.
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KingKota2001
Dodge Dakota
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6/05/2005
20:41:59
| RE: Oxygen Sensors
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After a few days of nothin' it threw the code again this morning, just a few seconds after I started it. Weird how it waited a dozen start cycles to come on again. And Branson...will the system go into closed loop with the MIL on, when the sensors eventually get to temperature?
Mopar8...if you'll keep me up to speed on your findings I'll do the same.
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Branson
Dodge Dakota
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6/05/2005
21:02:30
| RE: Oxygen Sensors
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If I remember correctly Open and Closed loop with the MIL on is conditional.
Still at work just now (yes, on Sunday), but I'll be able to give you a better answer one once I get home and can spend some time researching in the Service Manual. It's a CD version for my '04, so I'll be able to copy and paste into this thread.
While you're waiting, maybe some knowledgeable folks will jump in, and you won't have to wait.
P0141 AND P0161 still the only codes?
dickc's first post has some good ideas, though. If you can find the O2 sensor heater circuit relay, swap it with another of the same type (a/c relay would be a harmless swap if they're exact matches). Maybe you'll discover a bad or intermittent relay in the process.
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Branson
Dodge Dakota
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6/05/2005
22:56:08
| RE: Oxygen Sensors
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OK.
Here's some OPEN/CLOSED LOOP background info, copied from my service manual. Now I'm gonna go look look up the other stuff.
"
Effective control of exhaust emissions is achieved by an oxygen feedback system. The most important element of the feedback system is the O2S. The O2S is located in the exhaust path. Once it reaches operating temperature 300° to 350°C (572 ° to 662°F), the sensor generates a voltage that is inversely proportional to the amount of oxygen in the exhaust. The information obtained by the sensor is used to calculate the fuel injector pulse width. This maintains a 14.7 to 1 Air Fuel (A/F) ratio. At this mixture ratio, the catalyst works best to remove hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxide (NOx) from the exhaust. The voltage readings taken from the O2S sensor are very temperature sensitive. The readings are not accurate below 300°C. Heating of the O2S sensor is done to allow the engine controller to shift to closed loop control as soon as possible. The heating element used to heat the O2S sensor must be tested to ensure that it is heating the sensor properly.
DESCRIPTION – MODES OF OPERATION
As input signals to the Powertrain Control Module (PCM) change, the PCM adjusts its response to the output devices.
The PCM will operate in two different modes:
Open Loop and Closed Loop.
During Open Loop modes, the PCM receives input signals and responds only according to preset PCM programming. Input from the oxygen (O2S) sensors is not monitored during Open Loop modes. During Closed Loop modes, the PCM will monitor the oxygen (O2S) sensors input. This input indicates to the PCM whether or not the calculated injector pulse width results in the ideal air-fuel ratio. This ratio is 14.7 parts air-to-1 part fuel. By monitoring the exhaust oxygen content through the O2S sensor, the PCM can fine tune the injector pulse width. This is done to achieve optimum fuel economy combined with low emission engine performance.
The fuel injection system has the following modes of operation:
- Ignition switch ON
- Engine start-up (crank)
- Engine warm-up
- Idle
- Cruise
- Acceleration
- Deceleration
- Wide open throttle (WOT)
- Ignition switch OFF
The ignition switch On, engine start-up (crank), engine warm-up, acceleration, deceleration and wide open throttle modes are Open Loop modes. The idle and cruise modes, (with the engine at operating temperature) are Closed Loop modes.
"
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Branson
Dodge Dakota
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6/05/2005
23:34:08
| RE: Oxygen Sensors
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Here's some more stuf ripped from the pages of you-know-what(the spelling errors are not mine).
"
P0141-O2 SENSOR 1/2 HEATER PERFROMANCE
When Monitored: Engine running and heater duty cycle greater than 0%.
Battery voltage greater than 11.0 volts.
Set Condition: No sensor output is received when the PCM powers up the sensor heater.
Two trip fault.
P0161-O2 SENSOR 2/2 HEATER PERFORMANCE
When Monitored: Engine running and heater duty cycle greater than 0%.
Battery voltage greater than 11.0 volts.
Set Condition: No sensor output is received when the PCM powers up the sensor heater.
Two trip fault.
POSSIBLE CAUSES
-O2 SENSOR BELOW 2.52 VOLTS
-O2 SENSOR
-O2 RETURN CIRCUIT SHORTED TO GROUND
-O2 SIGNAL CIRCUIT SHORTED TO GROUND
-O2 SIGNAL CIRCUIT SHORTED TO SENSOR RETURN CIRCUIT
-O2 SIGNAL SHORTED TO THE HEATER GROUND CIRCUIT
-PCM
"
...Not a very helpful list, is it?
So I went out to the beast and looked under the hood. In the engine bay fuse box, or Power Distribution Center (PDC), the PDC cover shows where the O2 sensor relay would go, if I had one.
Didn't consider this fact when I posted earlier, but My Dakota is a 2004, and so has the New Generation Controller (NGC), which is the Powertrain and Transmission Control Modules merged into a single unit. Anyway, in my 2004, the NGC controls all voltages to and from the O2 sensors – the O2 heater circuit does not use a relay (that I can get to). I mention this because I realized my schematics for O2 power do not apply to your vehicle, and someone with 2001 schematics will have to give you that data.
Also, the info above may not be totally accurate for your year, as well.
Sorry.
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Mopar 8
Dodge Dakota
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6/06/2005
09:03:27
| RE: Oxygen Sensors
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Did some checking yesterday and the factory 2001 manual shows the 1 and 2 downstream sensers splicing together and using a commom circuit, I did notice that the ground strap from the body to the exhaust system was very rusty and after taking it a part it lookked like it barely had any contact, Cleaned and reinstalled the strap and reset the code, hasnt come back yet but I haven't started it too many times yet, The grounding point for the sensers is on the right front lower engine block if you have a 4.7 engine, it all fuses through Fuse U
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Mopar8
Dodge Dakota
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6/06/2005
12:23:59
| RE: Oxygen Sensors
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Well that dumb ass idea didnt work, light is back on this morning, found a website that has OE type sensers and very good prices, OxygenSensers.com. nearly 30 bucks cheaper than most parts stores and free shipping,I checked all the wiring harness and the factory code says heater element failure so I am just going to repalce the damn thing and get it over with,
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KingKota2001
Dodge Dakota
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6/07/2005
04:27:16
| RE: Oxygen Sensors
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Mine threw the codes again a day after I did the reset. Times are getting shorter between MILs.I think I'm going to get new ones also and hope that's it. At least that will eliminate those as suspects. I'll try the relay swap too. Since they're both tied together maybe it only takes one to go bad to throw a code for both heaters. Dig this thread up again when you've installed and tested them and tell how it went. I'll do the same. Branson...thanks for all the info. I'm learning a lot more on this subject than I thought I would ever have to.
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Dan M
Dodge Dakota
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6/07/2005
06:05:59
| RE: Oxygen Sensors
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when i replaced mine, i got a bosche from advance and it was $0.02 cheaper than the walker listed on oxygensensors.com
- Dan M
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