Okay, you X300 motorheads, I need some help! My Kitty is sick. She is a 1996 XJ6 4.0 lt. naturally aspirated engine with 205,000 original miles. I have had her for 14 years and have had no significant mechanical problems. I feel a slight miss at idle. The old gal is not very responsive to the throttle until I stomp on it. Then she stumbles and surges unevenly until I get to about 50mph and then she seems to even out. When I let off on the gas, she bucks, and sometimes, rather violently. She is coughing up two fur ball codes; P0300 and P1193.

I took her to two European auto repair “experts” and spent over $ 1500 and the problem seems to be worse. I’ll refrain from telling you what they supposedly fixed as not to bias what you may offer as solutions. As opinions are rendered, I will say whether or not it was “fixed”.

Thanks in advance for your help

 

Heated Oxygen Sensors – P1193
Model:
Jaguar XJ Range 1996, 1997
Complaint:
Fault code P1193 will most likely be set due to a H02S heater open circuit in the downstream sensor.
Remedy:
Switch off engine.
Check harness and connector condition and reliability, if a fault occurs then repair and go to step 7 of the test below.
Disconnect both downstream sensors and go to step 1 of the test below if no fault is found.
Test:


1. Ensure that each upstream sensor has a heater resistance between 5.3 and 6.7 Ohms. If this gives a positive result then go to step 2. If the limits are incorrect then replace the sensors, re-connect the harness and go to step 7.
2. Check harness continuity PI 126/003 is correctly wired to PI 127/003. If this gives positive results switch off the engine and go to step 3. If the circuit is open then find and repair the fault, re-connect the harness and go to step 7.
3. Check harness continuity PI 126/001 is correctly wired to PI 104/004. If this gives a positive result then go to step 4. If the circuit is open then find and repair the fault, re-connect the harness and go to step 7.
4. Check harness continuity PI 126/004 is correctly wired to RS 006/008. If this gives a positive result then go to step 5. If the circuit is open then find and repair the fault, re-connect the harness and go to step 7.
5. Check harness continuity PI 127/004 is correctly wired to RS 006/008. If this gives a positive result then go to step 6. If the circuit is open then find and repair the wiring fault, re-connect the harness and go to step 7.
6. Check harness insulation PI 126/003 will complete a circuit to ground. If this gives a positive result then reconnect the harness and go to step 7. If it short circuits then find and repair the fault, re-connect the harness and go to step 7.
7. Clear the fault. Then in order to check if the fault code has been cleared perform the service drive cycle. If this gives a positive result then stop. If the fault is still present then go to step 8.
8. Repeat the diagnostic procedure. If this now omits a positive result then stop.

When testing do not test the resistance between sensor pins 3 and 4 as the generated current can damage the platinum electrodes.

 

Thanks for the speedy reply! Rather than check them, do you think I should just change them? As far as I know, they are the originals.

 

Changing the sensors is throwing money at a problem and may not lead to a solution.
By doing a thorough diagnosis you will know what to repair.
If the problem is in the harness or a connector, replacing the sensors is like doing what you did for $1500 already, methinks.

 

Quick reply on the O2 sensor code is that it is a low priority in your engine regulation . The heaters are used in the first minute or so of the starting sequence and then shut off after the sensor is heated up and by the exhaust gasses . The sensors will not read the gas value correctly until the sensor gets up to it's own operating temperature independent of the engine exhaust gases and coolant temperature .

The OS sensor values are ignored anyway as the fueling operation is in the open loop mode until the coolant temp sensor reaches a certain value and then goes into the closed loop operation which is what you want .

On a practical side there are 4 wires on the X300 sensor connector . There are other types of O2 sensors and some are 3 , 4 , and 5 wire . The X300 has the often not used Titanium based sensor . From the Pic below you can see the 2 wires to check for the heaters are the same for all 4 sensors . Blue / Pink through White / Green . As Vee noted they should read the same in the 5.3 and 6.7 Ohms range . The Aft sensors are the ones used in engine regulation so hit these and clean the connectors and also the multi wire ground terminals along the upper aft firewall that shield the sensitive intelligence value wires returning to the ECU .



Now back to your priority on engine regulation . This $ 10 device on Ebay lets you see all your sensors values as you drive around and record on a multi sensor time graph to watch later at home . There are better versions of this devise software available then what is used in the video .

The most important sensors to watch are :

TPS

MAF

RPM

ECT

Short Term Fuel Trim which is a calculated final output of the previous sensors and the engine burn cycle process .

To get the big picture see page 54 in the PDF below :

http://www.jagrepair.com/images/Trai...20-%202000.pdf


Editing

 

If they are originals, then replacing them after over 200,000 miles probably inevitable, regardless of fault. It could end up being the fault!

You could do that, and then see what happens, or you can spend some time with a multimeter and alligator cables, and see what you find.

I suspect the P0300 code will work its way out once the P1193 code is resolved.

 

I respectfully have a different take on what to look at first the 300 code or the 1193 code for the O2 sensors . Even though the O2 sensors are important in engine regulation they are very fickle to even show . The most important item in the O2 sensors is the intelligence wire returning to the ECU with it's value . In theory if you get one heater code there should be 2 sensors to look at as they are wired in pairs as the heater electrical current is monitored in the ECU which provides the ground to operate .

The 300 code does not tell you specifically what sensor you have a problem with but through inference a suggestions on what you should look at this or that .

A more specific would be a P0340 code being a Camshaft sensor fail but where not looking at that in your example .

In a mastery approach ( I'm not saying I'm there ) to engine regulation as much information you can get the better you have in looking into the area of interest . The codes can give you a target as well as advice from others that can be broke down into 2 categories , what someone did to fix his or a percentage chance that it's that . There is also a least intrusive approach in time , cost , and effort consideration like changing plugs before coils .

One important thing in engine regulation is the foundation items often not thought of in looking for that magic bullet for a solution in the heat of battle . That would include items like fuel quality , filter , and pressure . Electrical power strength and return grounds . Consumable items such as coils , O2 sensors , plugs , and oil / fuel / air filters . ECU box connector pin condition . Air leaks . The troublesome Papa Indy 1 and 61 connector

Enough with the philosophy lets get you some basic information on your regulation sensors .

TPS should read 0.60 + or - 0.02 volt DC on the middle wire ( Green / Yellow ) as it goes over the fuel rail with just the key in the on position only not running . This reading should not bip to 0 as you slowly rotate the throttle though the range .



MAF should read 1.2 volts at the correct idle speed on the middle wire ( Green / Pink )




Crankshaft sensor should read 1300 ohms as a fundamental check , Clean the face of the sensor and the connector as a foundation item .

ECT should read page 78 of the Jaguar 801s document . My sensor specific P0140 code went away with a connector clean




These items must be covered first before you get into the items such as EGR and IAC valve as your build you information out toward a solution .

These items can be seen first without a $ 10 ELM327 device with the exception of the resulting Short Term Fuel Trim .

Editing

 

Thank you all for you input, especially Lady Penelope !! Please forgive me as I am a 70+ senior and all this info and technology is overwhelming! I have a OBD2 Bluetooth scanner talking to my phone using Torque Lite ( Torque Pro says there is something wrong with the adapter!) Trying to understand what all this info means. I am getting a message " Open loop due to insufficient temperature" and another Secondary Air Status " from outside atmosphere or off" Engine temp is 77 degrees C I don't know if this is telling me anything.


Also, forgive me, how do I get these voltage readings; do I unplug the sensor and read the pins ?

 

There are some Youtube videos on how to hook up your bluetooth ELM327 and don't forget to specify your vehicle make , model , and year .

The information of open loop is the key as you want it to be in closed loop fueling mode after it warms up .

There are 2 water temp sensors on the top of the thermostat on page 78 . the single wire runs the gauge in the cabin only . The one with 2 wires runs the ECU . clean the connector first .

The secondary is the smog pump . There is a fuse and a relay .

The outside air temp is the IAT ( inlet air temp ) sensor as it is installed on top of the 90 degree turn into the throttle butterfly

The voltage readings are as you have the connectors on the MAF and TPS and engine running with the exception in this case of the TPS

The ELM327 will give you a % on the TPS and you are looking for a slow smooth increase with no bips as this would be a bad spot.

The ELM327 will give you a grams / second on the MAF and you are looking for about 4.0 for the 4.0 liter and 3.2 on the 3.2 liter at idle . Most devices have this value off by a factor of 10 or 100 . The high on WOT is above 150.0

Keep asking questions

 

Hello again ! I just started back to working on my Kitty. I should mention, that the car was in Maryland at my son’s house and it pretty much rained the 10 days I was there, so I couldn’t do much.
What I did do was a lot of reading of the Service Technician’s training manual on the Emissions Control System. God, are these systems complex! Bring back Quadrajet carburetors !
Okay, so I should mention that I had to get the car back to Florida, so I took a chance and jumped on I95 and headed south. I figured if the engine blew up that would be one less thing I would have to deal with and the Insurance company would give me a room for the night and a car to drive home with!
Well, although the old gal didn’t want to get up and go without a lot of coaxing, once I got her up to 70 mph and put her into cruise mode, she did quite well. I could feel little hiccups, but I did average 23+mpg and the way back.
So now I am working with my ELM327 and my Android app trying to figure out what’s going on. I did find a blown fuse in the Secondary Air Pump circuit. I replaced it with another 25 and it blew again. Then I replaced it with a 30 and that is holding. I swapped out the Air Pump relay with the A/C relay and did not notice any difference and have still not blown the fuse.
I am still getting the same fault codes; 1193 and P0300 and the OBD scanner is telling me the engine is operating in “open loop due to insufficient temperature” and secondary air status is “from outside atmosphere or off”. I am still not sure if this reader is correct or not as it sometimes seems to be reading stuff and then sometimes not.
I am still wrestling with the connectors for the o2 sensors so that I can take some readings as Lady Penelope suggested, but I just can’tseem to get the harness to give me enough slack even though I have unwrappedthe wires from the supply harness. I will try again this weekend to get the clamps off the bell housing. Otherwise, I think I may just cut the wires. I already bought two new Bosch sensors to put in.
Also, I am going to buy a vacuum gauge because I am not getting a good reading on Torque. Can someone suggest a point a which to check the vacuum? I am also going to run a quick compression test next week and look at the plugs and replace them with Champion RY12YC
Any suggestions at this point would be greatly appreciated.

 

Insufficient temperature means the oxygen sensor is not telling the ECU that it's reached operating temperature aka you need to replace the oxygen sensor. Might as well do all four of them.

If it's not that, then your Coolant Temp Sensor is likely malfunctioning? Can you tell me what the coolant temperature is reading through the Android app? You should be able to get a reading on that. That's a $20 part and 10 minutes of your time.

The secondary air status is what it should be. Nothing to see there. It's either getting air from the air pump which it can get for 30 seconds at startup. (or some short time like that) or it can get it from the atmosphere, in which case, the air pump is turned off.

 

Someone recently found burnt wires leading to the smog pump . Based on that wouldn't be a bad idea to remove the conduit cover and inspect it . There was a TSB on uprating the fuse amperage .

Do not cut the O2 sensor wires as they are galvanized and don't take to soldering .

There is no MAP ( manifold air pressure ) sensor on this engine , some do .

My engine coolant temp sensor code P0140 went away with connector cleaning . Or in my case when the PO removed the connector during engine run .

The 2 O2 sensors to change for engine regulation are the downstream . The upstream are for Cat efficiency monitoring code P0420 and 430 .