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Closed loop fault

  • ksat22
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19 Oct 2021 01:57 #52115 by ksat22
Closed loop fault was created by ksat22
Hi, guys. I have a 2006 Jeep Liberty 3.7 litre which has a CL fault on bank 2 and a DTC for high voltage on the downstream O2 on that side. Short and long fuel trims on that bank look okay. 

I was unfamiliar on what a CL fault was so I looked it up and, according to the ONE article I was able to find on the subject, it apparently involves the PCM thinking there's a problem with the one of the upstream O2s. It went on to say that despite the hunch, the PCM still uses info on that sensor to adjust fuel trims and doesn't go into open loop or try to grab data from another banks' upstream.   

I guess my question here is, is the definition I found on the CL fault correct? Also, could the high voltage code I'm getting on the the rear O2 be related to that fault? I guess my thinking there is that, for whatever reason, the PCM thinks the info it's getting from the rear O2's is more reliable than what it's getting from the upstream one.

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19 Oct 2021 20:19 #52146 by Desmond6004
Replied by Desmond6004 on topic Closed loop fault
What is the actual number of the code please?

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20 Oct 2021 01:37 #52159 by ksat22
Replied by ksat22 on topic Closed loop fault
Just the 1.

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20 Oct 2021 01:48 #52160 by Desmond6004
Replied by Desmond6004 on topic Closed loop fault
Yes, but what is that 1 codes number?????
It's not P0001 is it?

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20 Oct 2021 02:10 #52162 by ksat22
Replied by ksat22 on topic Closed loop fault
P0158, I believe. I'll recheck it in the am.

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20 Oct 2021 13:18 #52171 by scannerjohn
Replied by scannerjohn on topic Closed loop fault
"I guess my question here is, is the definition I found on the CL fault correct?"

Long and short answer. Yes. As long as you understand that a DTC alone does not mean that sensor is bad or is the source of the problem.

"Also, could the high voltage code I'm getting on the the rear O2 be related to that fault?"
Yes.

"I guess my thinking there is that, for whatever reason, the PCM thinks the info it's getting from the rear O2's is more reliable than what it's getting from the upstream one."

No.

The strategy of the downstream 02 is to protect the catalytic converter not that it's more reliable than the upstream 02's. 02's can lie.

The P0158 is telling the PCM that the heater circuit on the down stream has a high voltage but it sees that the upstream is working. You reported the trims are good on bank 2.

I only addressed your questions not how to fix this. If someone else has a better answer or finds my reply in error, I hope you will post in.


 

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20 Oct 2021 14:27 #52173 by ksat22
Replied by ksat22 on topic Closed loop fault
Thank you for the replies thus far,,,,

"The P0158 is telling the PCM that the heater circuit on the down stream has a high voltage but it sees that the upstream is working. You reported the trims are good on bank 2."

I might be misunderstanding, but I thought P0158 was related to the sensor reading a rich condition in the exhaust stream, not anything heater element-related.

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20 Oct 2021 18:53 #52177 by Monde
Replied by Monde on topic Closed loop fault

Thank you for the replies thus far,,,,

"The P0158 is telling the PCM that the heater circuit on the down stream has a high voltage but it sees that the upstream is working. You reported the trims are good on bank 2."

I might be misunderstanding, but I thought P0158 was related to the sensor reading a rich condition in the exhaust stream, not anything heater element-related.
This may help you deal with the code. 

File Attachment:

File Name: 2006JeepLi...0158.pdf
File Size:1,471 KB

 


Never assume, diagnose!
Attachments:

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21 Oct 2021 12:16 #52192 by scannerjohn
Replied by scannerjohn on topic Closed loop fault
We all know how Paul feels about flow charts...

What diagnostic tools do you have to work on this problem? You mentioned that the STFT and LTFT for bank two were Ok so I assume you have a scantool.

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21 Oct 2021 17:51 #52195 by ksat22
Replied by ksat22 on topic Closed loop fault
I have an entry level Autel, model AL519 . In addition to displaying PID values, it can also can graph them, though only individually. It also has Mode 6 ability, which has been helpful.

I have been looking to upgrade, though, and I've noticed FORScan seems to be pretty popular on this forum. I've a little unsure what dongle would be best to go with it in that regard, however.

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21 Oct 2021 21:54 #52196 by scannerjohn
Replied by scannerjohn on topic Closed loop fault
Can you get the freeze frame data from your Autel as to when the P0158 set?

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23 Oct 2021 00:51 #52206 by ksat22
Replied by ksat22 on topic Closed loop fault
Fuel system 1 & 2 = CL
Load % = 58.8
ECT = 206 degree F
STFT1 = -0.8%
LTFT1 = 0
STFT2 = +0.8%
LTFT2 = 0
MAP = 8.6PSI
RPM = 1517
Speed Sensor = 31MPH
Spark Advance = 26.5 degree
IAT = 96 degree F
TP = 21.2%
Time Since Engine Start = 64 secs
Commanded Evap Purge = 32.9%
Fuel Level = 92.9%
Baro = 14.5PSI
Module Volts = 13.9
Absolute Load = 41.6
Commanded Equivalence Ratio = 0.999
Relative TPS = 6.7%
Ambient Air Temp = 69 degree F

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23 Oct 2021 12:18 #52222 by scannerjohn
Replied by scannerjohn on topic Closed loop fault
Before you do any visual and touch inspection of the S2 harness. Graph the B1S1, B2S1 and B2S2 sensors. Let's see their waveforms and voltages.

Do you have a volt meter?

Has the Jeep had any previous problems or repairs. How did the P0158 come about.

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23 Oct 2021 13:44 #52227 by Tyler
Replied by Tyler on topic Closed loop fault
Forscan won't help you on this Jeep, unfortunately. :( I have an AL519 as well. It'll show us Global O2 voltage PIDs, but not the true sensor voltage readings. Chrysler/Dodge/Jeep/Ram products use a 2.5V bias on their sensor ground circuits that cause the signal voltage to read 5V with the sensor electrically open (or with the sensor cold). But that may not be a huge handicap.

Because the freeze frame indicated the code set relatively quickly into an ignition cycle (64 seconds), I'm gonna guess that this isn't an intermittent problem. The flow chart Monde posted isn't terrible. :silly: Check that the sensor signal circuit isn't shorted to voltage, check that the return circuit isn't shorted to voltage, then short the signal and return together. If the signal now shows 2.3 - 2.7V (or 0V on your AL519), then the sensor has failed. :)

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24 Oct 2021 00:43 #52238 by ksat22
Replied by ksat22 on topic Closed loop fault
I think I know the possible reason for the code P0158. Due to a 0430 code (below threshold bank 2) on the vehicle, the signal wire going to the harness side of B2S2 O2 was disconnected and replaced with a jumper wire bonded to the signal wire on B1S2. This was done in an attempt to fool the PCM into thinking bank 2 cat was still functioning when in actuality it wasn't. I can't wrap my head around the exact reason for the P0158 the code, but I imagine it could be from the combination of a slightly richer fuel trim on that side along with the info the PCM is getting on B2S1.

Just to satisfy my own curiousity about the closed loop fault, I thought I might swap upstreams to see if it jumps to the other side. If it doesn't, I guess it would at least verify the upstream on bank 2 wasn't the reason.

To answer your questions, yes, I have a volt meter, scannerjohn. It also has a min-max capture ability also, in case that might be useful. I can take some pics of those graphs my dinky meter gives me- if you still think that'll be useful- but they'll probably be pretty crude compared to what you're used to seeing.

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24 Oct 2021 13:01 #52247 by scannerjohn
Replied by scannerjohn on topic Closed loop fault
Guess that answers the question of whether the Jeep had prior problems and or repairs.

You'll have to restore the wiring integrity and replace that cat before you can rely on any readings.

Upstream and downstream O2's function differently and report different signals to the PCM. We can discuss that unless you already know. Also Chrysler uses bias voltages on signal and ground wires. Because of this, it's a must to use OEM 02 sensors. NTK. After market sensors such as Bosch don't work correctly.

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24 Oct 2021 13:43 - 24 Oct 2021 13:44 #52248 by Tyler
Replied by Tyler on topic Closed loop fault

I think I know the possible reason for the code P0158. Due to a 0430 code (below threshold bank 2) on the vehicle, the signal wire going to the harness side of B2S2 O2 was disconnected and replaced with a jumper wire bonded to the signal wire on B1S2. This was done in an attempt to fool the PCM into thinking bank 2 cat was still functioning when in actuality it wasn't. I can't wrap my head around the exact reason for the P0158 the code, but I imagine it could be from the combination of a slightly richer fuel trim on that side along with the info the PCM is getting on B2S1.

This is much more likely to be your problem, IMO.

If you cut/disconnected the B2S2 signal wire and ran a jumper, then it's very likely that the jumper has an open or high resistance. That'd cause the B2S2 signal voltage to stay high at all times. Boom, P0158. ;)

I'd suggest putting the B2S2 wiring back to stock, clear your codes and see what comes back. If P0158 returns, you've still got problems. If P0430 returns, either find a different way to defeat the cat monitor, or live with it. Or, replace the cat.
Last edit: 24 Oct 2021 13:44 by Tyler.

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