4X O2 sensors and no 4WD

rdharms

rdharms

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Houston, TX
Looking for advice.

2005 LJR with 6 speed manual with 138k miles. I believe the exhaust is all original as it's in mediocre condition. I just bought this and it has O2 codes.

O2 sensors MIL
  • The previous owner said he would fix it so he sent a couple O2 sensors saying it would resolve the issue
  • I replaced 1/1 & 1/2
  • 4x O2 codes still present. Two logged codes (P0135, P0155) + 2 pending codes (P0141, P0161). These are the heating element codes
  • I checked the resistance on the sensors and they are in spec (~4-5 ohms)
  • I checked wiring back to PCM and it's good for the heater circuit and the sensor circuit
4wd and axle lockers not functioning
  • The 4wd indicator will not turn on when in 4wd
  • switch on T-case is bad. I jumpered it, no change
  • I chased wiring to PCM, all good
  • Based on service manual, the PCM send signal to ElectroMechanical Instrument Cluster (EMIC) via CANbus
  • Performed EMIC diagnostic routine, no faults. 4wd light turns on (not burned out)
Both these issues have a potential root cause of the PCM but there could be others like the Cats.

Any other diagnostics to determine what the issue is?
 
rdharms said:
Looking for advice.

2005 LJR with 6 speed manual with 138k miles. I believe the exhaust is all original as it's in mediocre condition. I just bought this and it has O2 codes.

O2 sensors MIL
  • The previous owner said he would fix it so he sent a couple O2 sensors saying it would resolve the issue
  • I replaced 1/1 & 1/2
  • 4x O2 codes still present. Two logged codes (P0135, P0155) + 2 pending codes (P0141, P0161). These are the heating element codes
  • I checked the resistance on the sensors and they are in spec (~4-5 ohms)
  • I checked wiring back to PCM and it's good for the heater circuit and the sensor circuit
4wd and axle lockers not functioning
  • The 4wd indicator will not turn on when in 4wd
  • switch on T-case is bad. I jumpered it, no change
  • I chased wiring to PCM, all good
  • Based on service manual, the PCM send signal to ElectroMechanical Instrument Cluster (EMIC) via CANbus
  • Performed EMIC diagnostic routine, no faults. 4wd light turns on (not burned out)
Both these issues have a potential root cause of the PCM but there could be others like the Cats.

Any other diagnostics to determine what the issue is?
Click to expand...

What brand O2 sensors? Only NGK/NTK are reliable. If you have an 05-06 the PCM’s are prone to failure. See @Wranglerfix
 
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Mark at Wranglerfix will test yours-

Likely your cats are failing as well...seems we are seeing a rash of that lately.

Specify Rubicon/241 OR on the switch and keep the receipt - aftermarket ones are hit or miss.

At this age these are typical issues.
 
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rdharms said:
rdharms said:
I have this same issue with all 4x O2 sensors throwing the heater codes on my LJR. P0135, P0155, P0141 and P0161. I just got this Jeep. The previous owner just replaced the battery prior to selling to me. I replaced Bank 1 pre and post Cat O2 sensors but didn't change anything. I have chased the wiring from the O2 sensors back to the PCM with no issue. The resistance on the O2 sensor circuit is ~5 ohms (in spec). When checking voltage at the sensor, it appears low (>8V). Does this point to a PCM failure? or needing new Cats?

I am also having issues with the factory locker system. The computer will not register that the T-case is in 4wd. I have chased the T-case sensor switch and closed the circuit. I know the circuit is closed at the PCM. Seems like multiple issues with a potential root cause of the PCM. Thoughts?
Click to expand...
Welcome

O2 codes are usually telling you there's something wrong with the cats. The sensors are doing their job.

The 4WD switch is not a simple open/close circuit.
You should start a separate thread.
Click to expand...

I meant you should start a separate thread for the 4WD switch issue, so it didn't get buried in the other O2 thread. ;)
All good.
 
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@rdharms It sounds like the PCMs has failed you. Faulty o2 sensor readings, loss of gauges and stalling while driving are the common failures. Are you having issues with the lockers activating?
 
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Well it turns out it was the PCM and the catalytic converter. Mark helped me a lot with the PCM replacement which got the 4wd and axle lockers working. Once the new PCM was running, it flagged P0421 & P0431 for low catalyst efficiency. Haven't had a chance to replace them.

This turned out to be a bad deal on the vehicle purchase. Wish I could go back and do some things different.
 
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Check out the thread on the cats for sale. Their about $250 on sale now which is a deal. Just replaced mine a month ago and paid 350.
 
Apparition said:
I wasn't going to order one but that price was too good to pass up so spare parts ordered.
Click to expand...

I just put a brand new banks cat back on that replaced stock with a busted hanger that I thought was doing the rattling. Well it wasn't the only one thing doing the rattling. Ordered this and new NTK’s from Rockauto. Still happy to save what I did!
 
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