The O2 Sensors start working as soon as they reach operating temperature (should be 20-30 secs after start). They are powered from the point of ignition on. You should try and graph the O2 sensor voltage. You can induce lean and rich conditions in the engine to see if the sensor voltage reacts.

The voltage should change high/low about every second. The actual voltages are not important, it's the change from high/low and low/high that is critical.

The difference with OL and CL is that in OL the signal from the sensors is ignored by the ECM. It is only in Closed Loop that the ECM will start changing STFT based on the O2 sensor signal.


I think the Temperature Sensor thing is not your issue. Closed Loop should happen well before 72 Deg C so something else is preventing Closed Loop (could be the O2 sensors themselves or something else - I'm not exactly sure of the full list of parameters)

 

Once the coolant thermostat opens and coolant flows past the sensor ( you can feel the upper hose to the radiator ) you should be in the ECU closed loop mode

But then the thermostat can be failed in the total open flow position and the coolant temp never gets up in range

ECU connector socket check ?

look for missing tabs on the sockets I have 5 tabs missing

If you change the thermostat the X300 does not take a O - ring as it will crack the thermostat casting , I have not changed mine so from reading

You can easily test the original thermostat in a pot of hot water and measure the opening gap

A new thermostat is not always be accurate but you can compare them to each other as you bring the pot of water temp up

 

Hi,

thanks to all your kind advices and help. Yesterday I changed the cooling temp sensor and drove on the highway to heat the engine up. To my surprise the temperature after that was only 75 degrees C. I removed the fuses F11 and F17 to shut off the fans. The temp rose to 104 degrees C or even more. I scanned the car and its still in open loop. The O2 show no sign of life. I then tried so switch the O2-connectors (see picture) but they won't open that easy. I was about to use stronger force or a screwdriver but before I'll attempt this and maybe damage them I was wondering about the colours. Looking from the passenger side (EU spec) the one on the left has a red, white and two blue wires. The right one three blue and a white wire.

When I look down where the O2-sensors are located and move the left connector its connected the one sitting on the right in the exhaust, and if I move the right connector its connected to the left O2-sensor. Is that mixed up or okay? Maybe someone has a wire-diagram? But even if they are mixed, they should show some movement right?

Thanks for your patience @all.

 

I failed to see your degree C and not F so disregard the lines on the thermostat .....bed time
r


Recommend pulling out the thermostat and a pot of hot water using a meat thermometer to watch the thermostat open as it approaches boiling

You may see the thermostat is already failed in the wide open position

On the sensor side of he connector they have the same 4 wire colors

On the ECU side of the connector they have 3 same wire colors and the 4th is different

Blue , Red , Green , Brown

I can see the Red one in the pic

It is this 4th wire that is critical and is a shielded wire with the ground studs on the engine firewall

The 2 sensors on this car is a platinum base and function different then the normal O2 sensor

Your reader may not account for this and only see them as the normal type of sensor or reject what it is seeing

 

I have the EU spec version, so only 2 O2-sensors. The thermostat can't be defective because the car gets warm pretty quickly and never falls down (middle of the gauge). Yesterday it went more to the right, which is also okay at 105 degrees C.

 

Don't move your O2 sensors. They are not your problem. If they were the wrong way around the engine would run very rough, and the STFT numbers would be very different to what you are seeing.

For your data and diagnosis, remember that the STFT is not a reading of the O2 sensors. STFT is the reaction of the ECM to the voltage reading from the O2 sensors. The STFT will only change in Closed Loop, regardless of what the O2 sensors is doing. So you cannot conclude from the data shown here that the O2 sensors are not working.

As I said previously, try and measure the O2 sensor voltages and see how they react to rich and lean conditions.

 

Ah, I see. Thank you very much. I always thought that the Trims are the actual O2-sensor readings. I have to buy a multimeter first. When I look at the colours, I guess my connectors are put the wrong way around!!??

 

No, unlikely. Plugging in the sensors the wrong way around would not prevent you from going closed loop, it would give you a wild idle though.

If you're buying a multimeter (which is a great tool to have), I would strongly recommend buying wire piercing probes. You'll be able to test readings while the car is in use.

If you're looking to take readings from the oxygen sensors, take the first reading close to the sensor, if you get readings, then the next reading you should take it at the ECU.

1. If you get readings near the oxygen sensor, then the sensor is at least working and sending a signal, if not, the sensor is dead. Replace.
2. If you get a reading near the ECU, then the sensor is successfully transmitting all the way to the ECU, and the ECU is now suspect. If not, then you have to start tracing the wire until you find the point(s) of failure.

 

You can monitor the O2 sensor voltages with your OBD tool. If fact it's better to do that initially, because that will show you what the ECM sees as the voltage.

As @Vee says above, if the ECM is not seeing anything then you will need to measure at the actual sensors and you will need multimeter for that (you definitely need a multimeter anyway ).

Here's some sample screenshots with the Autel tool.

1. Start position. Engine just started. OL, O2 voltage low, STFT 0
2. 20-30 seconds after engine start. OL, O2 voltage now rising to high as it warms up. STFT 0
3. Induce a Lean condition (by pulling off Vac pipe on inlet manifold. O2 voltage drops but STFT stays 0 as in Open Loop.
4. Just entered Closed Loop. O2 volts high, STFT just starting to move to -ve.
5. Normal operation at idle, Closed Loop. O2 voltage moves high and low. STFT flexes slightly as O2 voltage changes.

 

1. I always recommend D900 over ELM as cheapo OBD scanner. Works perfect with X300, shows o2 sensors too and you might be able to get it in Germany too.
2. Measuring o2 sensors directly with a digital multimeter isn't going to do much, you can just about measure 5 or 0V, you wont be able to check for switching, which is important here. You'll need an oscilloscope or an old school analogue meter to do any kind of meaningful troubleshooting.
3. CTS at under 80C is fine.
4. You'll probably have to fork out for new sensors, they are old and lazy anyway and suppose to be changed. My guess is that heaters are shot hence they don't 'close' anymore.
5. You can definitely do it yourself, you can get to one from the engine bay, just cut off the wires as low as possible, then normal socket over it and 4 or 5 extensions and it will come out. The other one can be accessed from underneath the car, you will need to get it up enough to actually get underneath it, normal spanner will get it out although open ring spanner is preferred.
6. I highly recommend getting a tap and rethread the hole after removing old o2 sensor. They are often messed up and it easy to cross thread new sensor.
7. You wont pass your test until the o2 sensors show closed loop. Good luck.

 

Look again at the colours please which Parker posted: R and U. Red (bank2) and blue (bank1). My picture reflect exact these colours! So its mixed up!!! Maybe they are dead too but still mixed up. It has a rough idle and only gets smoother when its hot.

 

thank you very much! I guess my thermostat stays open all the time hence the problem to heat up properly. Also the upper hose was hot. Would be cold if thermostat was closed. But thats not a big problem, I can swap it on my own but the car gets to normal temp (gauge) in no time, never decreases whether winter or summer.

 

b1mcp, katar83: your kind help and advice is much appreciated but its late in germany and I will check later.

 

It has a rough idle and only gets smoother when its hot

The O2 sensors must be heated up to properly read , after a while and running they may get to this temperature and read and send the correct signal to the ECU . Before the exhaust gasses can get the O2 sensors to " their temp " the ECU will command that power goes through each O2 sensors heating element . On each sensor connector it is the same wire colors of Blue / Pink and White / Green on the ECU side of the connector so you would have to match the wires on the sensor side of the connector . With a meter it is easy tp check on the sensor side of the connector to see if you have a bad heating element inside the sensor . There is a cheap connector already installed Bosch sensor that is common available . There is one fuse for a 2 or 4 sensor setup and is # 14 / 10 amp right engine bay fuse box .Between the fuse and the O2 sensors heating element the wire passes through the Papa Indy 61 connector at pin 12 as the White / Green wire that has had corrosion problems from reading and there is a Jaguar TSB on this connector in the link below . If there is corrosion present on this pin it would limit the current to properly operate the sensors heaters even though you may see 12 volts with a meter as soon as you rotate the key to the run position before starting the engine .

05.1-14 (jagrepair.com)

This applies to both connectors next to each other and you may find different connector body colors like 2 black ones

If you find a fault with the connector you can bypass the connector on this wire before replacing the connector

Corrosion can be hidden as the wires exit the connector other then the front faces that mate to each other

You will find extra wires on one side of the connector halves and not on the other halves , These extra wires are for the V12 engine








It is a 13 pin connector and you can see the # 12 to the left in this picture







The ECU may not but should be able the show a code for failed O2 sensor heaters but..............

75 C and even better 104 C should be hot enough to trigger ECU closed loop mode

Without knowing what the temp point is to be in open or closed mode you may be in open mode at 75 C and closed at 104 C

The temp gauge on the dash should not be referred to as this gauge is not accurate in how it behaves .and is the other single wire sensor on the thermostat housing

 

The Jaguar is odd, in as much as both sensors have the same connector, so in practice, can and do get ‘mixed up’. HOWEVER, once installed there is a software procedure called ‘Sensor orientation’. This tells the ECU to work it out for itself which sensor is which! This is in dealer level software and you would need to find a Jaguar specialist that has it.

This is meant to be run after the sensors are changed to avoid the mixup, but if you change them one at a time you will not get in a muddle.

Your wiring may LOOK wrong, but if the software orientation has been run (when they were installed) it doesn’t matter……

 

If the O2 sensors were mixed up then the opposite would be true. As we know the O2 sensors are ignored until car warms up and Close Loop happens. It would be at this point that rough running would happen if the sensors were mixed.

In Open Loop, the ECM just uses a default fueling map based on other parameters (temperature etc.).

 

…and we’re back to where we started.

Replace the oxygen sensors.

You only have two sensors, so if you start up the car and the idle is wild, you can just unplug them both and switch it over. Imagine the confusion if you had 4 sensors like we do in the states! Basically, let’s not worry about if the sensors are switched just yet, it’s a 2 minute solution.

 

Bosch Exact Fit Oxygen Sensor # 13789

The sensor pigtail wires are a special galvanized wire and are very brittle so care must be taken to not let the wire twist and break during installation

When I received my car from the previous owner it had broken wires sticking out of the insulation near the sensor

They can not be solderd

The new sensors may need some engine run in time before they work perfectly and observe their performance

Dónt forget anti seize on the threads only and never excess on the bulb'

A missing crush washer seems from reading to make a difference and should be included but one from a cheap spark plug will work

Hex Size = 17mm

I have the cheap spark plug # in the garage somewhere and is either a 12 or 14 MM thread size different then the X300 engine spark plug

There are 2 ground wire studs on the rear engine firewall that are critical to protecting the return wire to the ECU signal and can be cleaned before purchasing and replacing the sensor as a cheap try

By removing the O2 sensor connector you may find some corrosion on he pins like on mine

In the end a short term fuel trim of + or - 3 % from a target value of 0 % is reasonable through all throttle and engine load resistance ranges

There was a Jaguar TSB to uprate the smog pump fuse size and the pump can fail without popping the fuse as the wire harness can short out

There is a diode in the wiring harness and can be easily checked with a meter

The Smog pump can be removed or left in place and run with a battery charger or battery using battery jumper cables

Fuse # 7 / 25 amp right engine bay fuse box and I believe it was uprated to 30 amps

There is a specific smog pump relay that can be swapped

See page 17 as right # 4 secondary air injection control and can be swapped with the right # 3 but not # 5 as this powers the ECU and half of the engine regulation sensors

X300 1996 LWB.pdf (jagrepair.com)

You may not have a smog pump in the German market vehicle

See page 93

www.jagrepair.com/images/Training Guides/801S - 2000.pdf

There is a smog pump check valve that can be checked also

There is also a electrically controlled check valve inside the smog pump itself

The smog pump only runs in the idle speed range to pass emissions test

 

OMG Parker I am german so give me some time please haha. Thanks bud! I chatted with Pete and the Bosch seem to be the OEM but they are 135.- € each in germany so I am willing to give bristishparts a try.

I could use contact spray on the connectors and swap them for testing but they are really tight and the "ELM" shows no reading.

Its an Euro spec car, I don't have that pump. Talked to a mechanic and he said pull off the crankcase ventilation to pass the emissions test because my oil is too old and full of gasoline leftovers. BUT: the officials will see it, the car will suck false air in

 

While waiting for the part, you might want to start spraying down the nut with some penetrant. Something to help get the darn things loose!