Land Rover Repair: Error code 1158, cat converter, o2 sensor

Question
Hi John,

I just read your response to Vince regarding his Dico. OBDII code 1158 problem.  I have 95 RR 4.0SE and has same error code 1158.  I swap the after cat. converter O2 sensor (left & right) and got same code.  I than measure the cat. converter temp. and found passenger (right) side is about 60F lower than driver (left) side.  My friend told me it is because the passenger side cat. converter is degrading and not function properly.  I also disconnect the passenger side after cat. converter O2 sensor and got the same error code 1158.  I do not see any misfire error code (I did see it come out once about 8 months ago and never see one since then after I clear the code).  Is my cat. converter not functioning properly or something else cause the 1158 error code?  Please help.

Answer
Hi David,

sometimes this code is triggered when the connection is faulty. Make sure the wire and connector are free from grit and oil and that the connection is solid.

As for the cat question, you should hear a difference when the cat begins to fail.  I had terrible noises when it finally happened...then it went silent.

There could be many reasons why one side is hotter than the other.  Engine wear, exhaust trouble, spark problems, cooling troubles, air flow ability...

Best of luck,

JohnMc