Today I worked on a problem child vehicle. It keeps on throwing a P013C code. (Bank 2 Sensor Slow Switching) From what I have read this code is due to it failing a test that watches how fast the rear O2 sensor switches from normal rich bias to lean on deceleration. In a road test this was the case. When going from highway speed off an offramp it tripped. Although all the O2 sensors seemed to work, both the rear O2 sensors and the catalytic converters were changed. The shop told me that they checked for exhaust leaks. Exhaust leaks seemed to be the common theme I have been finding out there.
Here is the strange part. The long term and short term combined are at 20% at 2300 RPM. Above and below those RPM it is closer to 10%. The first picture is of the two front O2 sensors. (At 2300 RPM) The Orange line seems to be biased slightly rich. The Blue line seems to switch more and work more like I would expect. The second picture shows the rear O2 sensors. See how one is slightly higher than the other? When running the vehicle at 2300 RPM they will match each other for a while. After back to idle the Orange line drops but the Blue one takes a while. At Idle the sensors read perfectly.
We thought maybe there was something awry in the engine computer so we got one from a wrecking yard and tried it. Same exact readings. So we have moderately high fuel trim at idle and high fuel trim at 2300 RPM. Above 2300 it comes back down. I am really wondering if the high fuel trim is making the vehicle set the code when coming down. So the question is what would make the vehicle lean at cruise and slightly lean at idle?
Some of the Google research I found that one solution was replacing the MAP and PCV. This would make sense if the MAP sensor was dogging when vacuum reached a certain point. Tomorrow, I am going to watch the MAP and see if something goes weird with it. This would explain the fuel trim at mid range. I think we can rule out vacuum leaks.
What are your thoughts?
Hey Michael, it seems most times I have seen slow response codes I end up finding exhaust leaks, heater circuit failures, or a failing sensor. Have you checked heater integrity of the sensor? You could also try moving the sensor to the other bank to see if the symptoms follow the sensor.
Hi Pat, Thanks for responding. I have watched the heater values. They are being controlled by the PCM but seem to be working all about the same. The front sensors have not been swapped but the rears are new. The problem existed before they were replaced. The shop I am working with is an exhaust shop and they have gone through the exhaust looking for leaks. I really think that what is happening is that during cruise the Long Term trim gets up to 20% or so. Then during deceleration there is an initial hit of fuel based on the high fuel trim hitting the cat and lengthening the time before the rear O2 volts drop. I think if I can correct the fuel trim the other will fall into place. Just a theory at this point. Great input!
Your theory seems sound. My only comment is I would expect the MAP to create that reaction on both banks(I could be wrong on this). I have seen A/F sensors on V6 and V8 Toyotas to cause a down stream to set voltage stuck high and slow responses codes and this scenario reminds me of that.
What brand o2 sensors were used? Ive been bit on Mopar if you don't use their oxygen sensors...not sure why.
I believe the customer told me that the replacements were Denso or NTK.
Hi Michael, FWIW, I have had issues with Denso sensor in Dodge vehicles before, the only time I have ever had issues with that brand. I don't think that's your issue, I think the high fuel trim is probably the issue, just a heads up.
Just a thought, we are 98% import mostly European but do get an occasional domestic, I remember years ago getting a 2009 Jeep 3.7 with the same code which ended up needing a software update.
Thanks for the suggestion. The latest update was confirmed in both the original and the donor Powertrain Control Modules.
Here's some screen captures I have of a Toyota setting a slow response code on the downstream. The upstream was lying and reading a false rich. Again not sure if this is gonna help at all but this just reminds me of what you have going on. It threw me for a loop cause it was so slight and took a lot of studying to catch.
I will be taking a look at the vehicle tomorrow. I was told the technician was going to swap the left and right sensors to see if the patterns changed. We will see what happens.
Today the customer changed both front O2 sensors. The scan results remained the same. We tested the MAP sensor readings as compared to a vacuum gauge. The results were the same. We found a small intake leak at the PCV.
The fuel trims remain at around 10% at idle and 20% at cruise. I ran out of time but at the end of the day today the light bulb came on. What about fuel pressure? There are not driveability concerns but I am not able to explain the fuel trim. The customer is going to do an injector clean and at the same time watch the fuel pressure to see if it is too low.
So were the rear sensors switched bank to bank? I would want the vin & part numbers of the sensors that were installed.
Hi Glen, Rear sensors were swapped side to side. Results were identical. VIN 1J8HG58208C111300.
BTW, This is a 5.7 Engine not a 4.7 Engine. I am not sure what I did wrong in description but I do not see a way to change it.
Thank you for the information. I believe that the O2 sensors are a distraction to the real issue causing the trouble code. The fuel trim is where I believe the problem is. All four of the O2 sensors have now been changed. Both converters are new. All exhaust leaks repaired. Combined fuel trim at idle is now 11% and at 2500 RPM 22%. The theory is that the high fuel trim is tripping the code during deceleration. The shop was going to test the fuel pressure and do an injector clean to improve the fuel trim. The vehicle does not have driveability issues.
The end user customer needed the vehicle to go on vacation so the diagnostics are delayed until they get back.
Thanks for your help. I am hoping to get a final answer on this one next week.
I have a shop who contacted me with this same code on the same vehicle just this past week. I will let you know what I find with mine. The only thing I would say since you mentioned that the stop checked it for leaks, is that I would check it myself. How did they check it? Smoke machine? Shop vac with soapy water? Nearly every time I see this code it's a very small leak in the exhaust and always sets on decel.