Afternoon all

I changed my catalytic converters today due to an MOT failure on emissions. I planned to change both O2 sensors as well. However that was a fail because I cannot understand how I am supposed to access the connectors and route the wires. The car only has 2 sensors - these are before the main cats. I can see the wires running through a clip attached to the gearbox, This clip seems to be a loop of metal with no opening to remove the cables. It is held on by a large difficult to access bolt (hex or torx, not sure) on the engine facing side of the gearbox. So thats problem number one. Then above that there is an open metal clip - again very difficult to access but do-able. Then things get really bad. I can see the plugs that are on the bulk-head, directly in line with the end of the fuel rail but they are totally inaccessible. There is a metal bracket held on with a 10mm bolt. Managed to get that out but although I can then twist the bracket and see the connectors better, there seems no slack at all to be able to properly access them. The wiper motor is in the way as well but removing that isn't going to give me much more access. On the bracket is another connector that I can remove easily but the O2 plugs seem impossible.

Anyone have any ideas?

Thanks
Sam.

 

The rear O2 sensors connector mount position come in 2 forms with the upgrade referred to a the Lama mod

The 97 probably has this mod as my 96 was not difficult to get to the rear O2 sensors

There is a map to know the connectors are in correct spot as the pair can be easily mixed ( many people done )

On my 96 the wires go down the cars right transmission / engine split and trying to remember if the clamps were open just slip in pigtails or the clamp has to come all the way off

Be careful to not twist the O2 sensor wires as very brittle galvanized wires like a chain link fence , my O2 sensor wires were broken and sticking out of the wire's insulator .......................Wow

More text and pics coming

 

There is 1 fuse for all 2 or 4 ( US ) heating elements inside the sensors to be at operating temp for them to read correctly ( sensor physics )

This fuse is either one single # 10 , 12 , 14 , or 16 right engine bay fuse box

 

What you describe is like mine the 3rd connector is a single heavy white wire for the starter solenoid relay

The O2 sensor correct position is based on the car side of the O2 sensor connectors 4th wire as 3 are going to be the same

So you will see either red or blue color 4the wire

Check for green corrosion on the connectors and there is a small ground stud on the rear engine firewall to clean that protects the very sensitive O2 return signal

The original O2 sensors can be cleaned with gas and Seaform maybe , and there is a crush washer ( 12 mm ) needed for correct reading from reading someone else even through this specific sensor does not get a ground through the mounting threads and exhaust system like older cars

Do not get anti seize compound on the tip of the sensor

A 12 mm cooper crush washer can be obtained from a cheap 12 mm spark plug , the X300 spark plug is a 14 mm crush washer

The X300 O2 sensor hex nut is 17 mm and may be able to remove with common tools , but my pipes where hanging loose giving me room

 

Hello Parker,

nice to see the colors in the original schematics of which pipe is what harness. I was trying to figure it out myself, did not think of coloring the charts. Anyway my problem with o2 sensor got progressively worse. I had generic OBDII diagnostic tool which gave me following results, suggesting that one sensor is dead other was ok. My is 4.0L 1995 VIN:733433

• I have 2 sensors only, all sensors are then stated as S2
• In the beginning there was signal on
  • Bank2 1.215V short term trim was working
  • Bank2 0.01V and completely flat dead
• When i switched the wires to check whether the problem is not in harness, the voltage showed up in Bank1, so the harnesses were OK.
• Tryied to remove one of the oxygene sensor (now I am not sure which it was whether 1 or 2).
  • did not succede as I had too weak tools apparently
• Now everything is dead no voltage anywhere

My questions are:
1. Could I kill the harness wires?
2. Where is that ground connection that passess: "stud on the rear engine firewall to clean that protects the very sensitive O2 return signal"
3. Can I check the system by giving false resistance instead of the oxygene sensor? If so, do you have some idea of the range of the resistance the sensor is providing?

Thank you very much Vitek

 

A little tread highjack but related,

I have euro version 1997 3.2 X300, there is only two O2-sensors on the car and I have not found any loose plugs for the other two

BUT

The sensors I have in my car are located "downstream" like in the picture below. Upstream has no sensors, bank 1 hole is plugged with blind plug and bank 2 hole has plug with few centimeters of steel pipe that has been cut and kinked shut. I think it is for secondary air pump, as there is no EGR valve in this car.

Are the 02-sensors really supposed to be only downstream after cats or has some done some interesting modifications to my car?😅



[/QUOTE]

 

Only US (and Canada I think) have 4 O2 sensors. Rest of the world has only 2 sensors.

 

The rear O2 sensors on my USA model are between the fwd most cats ( cats pointing up 45 degrees ) and the aft cats ( middle of car below front passenger seat )

This for a 4 cats system

The previous owner on yours may have installed the incorrect type of O2 sensor as should be Titania based and not the more common type , or the reader device may not have or can not read this type

The other type generates a variable voltage from a ground wire , the Titania varies in resistance from a feed voltage and the resulting voltage is read by the ECU

A good explanation and expected voltage values of the Titania is on page X of this Jaguar 801s doc ( there are 3 engines in this doc as yours is a AJ16 series )

 

The downstream sensors are for engine regulation ( fuel mixtures / trim ) all of world and the upstream sensors installed in North America only are to measure catalytic efficiency ( good enough exhaust gas products conversion effectiveness ) down the flow path as CEL code P0420 and P0430 abouts

There is 1 fuse for all O2 sensors as they must be heated in normal service as you start the car for them to heat to a certain temp to even read correctly ( sensor element physics )

# 14 / 10 amp red , right engine bay fuse box

On each sensor themselves there are 2 pins as the heating element that would read the same resistance for all O2 sensors , as long as it is not an " open " or infinite resistance value

The original O2 sensors are from Denso and connector ready equivalents are Bosch # 17389 and a Walker brand number others have found ( both were hard to obtain in hand recently back from reading others )

If someone used a " universal equivalent " with no Jaguar connector the wires are almost impossible to solder or splice effectively as the wires are galvanized ( no solder wicking action ) and brittle , the brittle makes them break wires on the sensor hex twisting into the downpipe threads , so the not loading up of twist in wires must be adhered to , mine came with broken wire strands sticking through the wire insulation , wow

Remember to use anti - seize on the sensor threads only and not the sensor tip as this ruins them , a 12 mm crush washer ( from a cheap 12 mm spark plug ) is used on installation ( mine came without ) and someone in Boston observed this made a difference on his , installation hex size 17 mm


Got your Doc link as page 80 for the AJ16 engine , a really deep explanation of the engine regulation is at the beginning of the doc from the page 1 fwd

801S TITLE

 

Hopefully you got this sorted out Sam. I have the US version and replaced all 4 sensors a couple of months ago. The two that you struggled with were also a total pain for me as well. I disconnected the third connector on both sides, which I had to go under the car to retrieve when it came time to reconnect. Then I disconnected both of O2 sensors from the top side, which is the side that goes back to the ECU which gave me just enough room to disconnect the bottom side from the bracket. Doing one at a time is impossible. I have smallish hands which helped. I also found out that even though mine were reconnected properly per the drawing they were still backwards due to sometime the ECU is programmed backwards. I found that out by chance in another thread. A telltale sign that they are backwards is getting the multiple misfire code after your'e done. I had to go back and swap mine so I had to do it twice. I never did get the bracket remounted. It's zip tied out of the way currently. The only other idea I had is to remove the sensors while they're connected which would require the wires to be twisted 3 or 4 turns and then untwisted as you thread them into the manifold.

 

This is strange order for 02-sensors to work, as normally, the downstream sensors measure catalytic efficiency and upstreams are used to adjust fuel trim, because if the catalytic converter works, signal is flat. Thats why I was confused but didnt realise that these are pre-cats and there are main ones under the car.

Apparently these pre-cats after exhaust manifold are not doing very much if in 2-sensor car, they measure after them. They might have something to do with the secondary air pump system more than being effective converter?

 

Nothing to do with Air Pump as this only operates on initial startup for about a minute.